https://www.perplexity.ai/search/ive-opened-a-couple-malfunctio-QDKV6HJiQ.KjKnybpZ63Tw#6
I’ve opened a couple malfunctioning keyboards and I’m impressed by their simplicity as well as their mysterious delicateness. One of the things that surprised me was the presence of traces traveling through multiple keys. How does the circuitry for identifying which key is pressed tend to work? <img src="https://r2cdn.perplexity.ai/pplx-full-logo-primary-dark%402x.png"; style="height:64px;margin-right:32px"/> # How Keyboard Circuitry Detects Key Presses **Keyboards commonly use a matrix circuit design to identify which key is pressed, balancing simplicity and hardware efficiency.** ## Matrix Architecture Explained Inside most keyboards, especially membrane and mechanical types, the keys aren't wired individually to the controller. Instead, the keys are arranged in a grid (matrix) of rows and columns, with electrical traces running horizontally (rows) and vertically (columns). Each key sits at the intersection of one row and one column trace. Pressing a key physically connects its specific row and column traces together via a switch. **Why are traces shared among keys?** By arranging traces in a criss-cross matrix, many keys can be identified with fewer wires than if each key had its own dedicated circuit. For example, a 5x14 matrix can handle 70 keys with only 19 lines, instead of 70 individual wires. ## Key Identification Process 1. **Microcontroller Scanning:** The keyboard's microcontroller scans all rows and columns rapidly. Usually, it sets one row "active" and checks which columns respond. If there’s continuity for a row-column pair, the key at their intersection is pressed. 2. **Sequential Scanning:** The controller activates one row at a time while reading all the columns, then moves to the next row. This cycle repeats thousands of times per second, making the detection virtually instantaneous. ## Ghosting and Diodes In some keyboards, pressing multiple keys can cause "ghosting" (misinterpreting which keys are really pressed) because current can flow through unintended paths in the matrix. To prevent this, many higher-quality keyboards add diodes (one-way current valves) in series with each key. This allows accurate multi-key rollover without ghosting. ## Why the Circuitry Feels Fragile The "mysterious delicateness" comes from the fine conductive traces (often printed on flexible plastic sheets in membrane keyboards or on circuit boards in mechanical keyboards) and the flexible contact domes or switch mechanisms. These are engineered for millions of actuations, but physical puncturing or contaminant exposure can easily break traces or contacts. ## Summary Table: Keyboard Matrix Circuit | Feature | Description | | :-- | :-- | | Trace layout | Grid of intersecting rows and columns (matrix) | | Key switch location | At each intersection of row and column | | Signal detection | Microcontroller cycles through rows, senses columns for closed circuits | | Trace sharing | Each trace services multiple keys, drastically reducing wiring complexity | | Ghosting prevention | Diodes may be added for correct multi-key detection (anti-ghosting) | | Physical construction | Thin, flexible traces and contact domes often create a delicate feel | Essentially, modern keyboard matrix design is a triumph of cost- and space-efficient engineering, enabling fast, accurate key detection with relatively simple, but elegant, circuitry. --- I’m working ln a specific laptop keyboard with traces on two layers of flexible plastic. Upon inspection, the thing looks like it would be waterproof! However, keys stopped functioning correctly after exposure to rain. Another had a ripped flexible cable, which I attempted to replace, but the cable appears to seat and contact via pressure to both sides, and strangely seems more sensitive to placement than the apparent width of the traces it contacts. What is a good way to test or diagnose a keyboard like this? Is there some way to affix test leads to thin traces or cables? Or should I find a broken motherboard and find a way to affix leads to its solid traces? # Diagnosing Laptop Keyboard Flexible Cable Issues Given your specific situation with a two-layer flexible membrane keyboard that appears waterproof yet failed after rain exposure, and a damaged flexible cable connector that's finicky about placement, here's a practical diagnostic approach. ## Understanding the Problem **Why "waterproof-looking" keyboards fail:** While the plastic membrane layers themselves are waterproof, water damage typically occurs through trace corrosion rather than immediate electrical shorts. Rain exposure can introduce contaminants that corrode the conductive ink traces over time, and these corroded spots may not be visually obvious. The traces are essentially printed conductive ink or carbon, which is vulnerable to oxidation and chemical degradation.[^2_1][^2_2][^2_3][^2_4] **Why the cable connector is so sensitive:** Zero Insertion Force (ZIF) and similar pressure connectors rely on precise alignment between the ribbon cable contacts and two rows of pins in the connector. The cable contacts are wider than the individual traces they eventually connect to, so even slight misalignment can cause some keys to work while others fail. The connector makes contact via pressure on both sides of the cable simultaneously, and this contact quality degrades easily.[^2_5][^2_6] ## Diagnostic Approaches ### Testing the Membrane Itself **Multimeter continuity testing** is your primary diagnostic tool:[^2_7][^2_8][^2_9] 1. **Set your multimeter to continuity mode** (typically produces a beep when resistance is below 70 ohms)[^2_7] 2. **Identify the matrix structure:** Each key sits at the intersection of a row and column trace. Place one probe at the ribbon cable connector end of a suspected trace and walk the other probe along that trace, listening for continuity[^2_7] 3. **Important caveat:** Long traces have inherent resistance. A non-beeping multimeter doesn't necessarily indicate a break—you may need to reposition the common probe closer to test sections of long traces[^2_7] 4. **Mark and map traces:** Use dots and dashes or other unique patterns to mark each trace as you follow it, since multiple traces run in parallel and can be confusing[^2_10] 5. **Test key contact points:** When you press a key location on the membrane, the top and bottom layers should show continuity between their respective row and column traces[^2_8][^2_9] ### Addressing the Cable Connection Problem For the sensitive FFC (Flat Flexible Cable) connector: 1. **Clean the connector contacts thoroughly:** Use isopropyl alcohol (90%+ concentration) with a small craft pipe cleaner, moving up and down (not side to side) to avoid bending pins. Alternatively, use DeoxIT contact cleaner[^2_11][^2_12] 2. **Clean the cable contacts:** Wipe the exposed metal contacts on the flexible cable with isopropyl alcohol and a lint-free cloth or paper towel[^2_12] 3. **Ensure proper seating angle:** The cable should be inserted at a slight angle (like a plane landing) then laid flat, with the exposed contacts facing the correct direction (usually downward toward the bottom row of pins)[^2_6][^2_5] 4. **Apply consistent pressure:** If the connector latch is intact, you can supplement it with Kapton tape to maintain pressure across the entire cable width. Kapton tape is heat-resistant and thin enough not to interfere with the connection[^2_5] 5. **Live testing:** Keep the laptop powered up (if safe) and test keys as you adjust cable positioning to find the sweet spot[^2_5] ## Practical Testing Solutions ### For Flexible Membrane Traces Unfortunately, attaching traditional test leads to thin conductive ink traces is extremely difficult. Here are your realistic options:[^2_4] **Option 1: Test at the connector points** The gold-plated or conductive pads where the flexible cable plugs into the keyboard are your best access points. These are solid enough to probe with multimeter leads.[^2_3][^2_10] **Option 2: Pogo pin test fixture (advanced)** Spring-loaded pogo pins (test probes) can make temporary contact with flexible circuits. However, creating a custom fixture requires:[^2_13][^2_14][^2_15] - Identifying exact test point locations - Mounting pogo pins in a rigid holder aligned to those points - This is overkill for a single keyboard repair but useful if you repair many[^2_14][^2_15] **Option 3: Direct cable shorting (temporary diagnostic)** If you only need to type a few characters, you can manually short the connector contact pads with a small piece of wire to simulate key presses. This confirms whether the problem is in the membrane or the cable/connector.[^2_3] ### For Broken Motherboard Connector If you suspect the motherboard's ZIF connector is damaged, testing on a broken motherboard's connector would indeed be easier since its traces are on a rigid PCB. However, sourcing an identical connector from a broken board requires finding the exact same laptop model.[^2_16][^2_1] ## Repair Considerations If you locate broken traces, repair options include: **Conductive ink/paint pens:** Products like CircuitWriter or CircuitScribe silver pens can repair corroded traces on flexible plastic. The ink must be:[^2_2][^2_17][^2_18][^2_1] - Shaken thoroughly before use - Applied carefully to avoid dissolving adjacent traces - Allowed to dry completely (several hours) under airflow - The repair is moderately durable but may not survive repeated flexing[^2_17][^2_18] **Copper wire with adhesive:** For straight-line breaks, a thin copper wire can be taped over the damaged trace, though copper oxidation can cause eventual failure[^2_2] **Replacement:** Given the difficulty of repair, sourcing a replacement keyboard assembly for your specific laptop model is often more practical[^2_1][^2_4] ## Rain Damage Specific Issues The rain exposure likely caused internal corrosion rather than immediate failure. Even though the keyboard looked waterproof, moisture can:[^2_19][^2_20] - Enter through the cable connector opening - Condense between membrane layers in humid conditions - Introduce salts and minerals that corrode conductive traces over time - Cause oxidation on the connector contacts themselves[^2_21][^2_19][^2_1] This explains why the keyboard appeared physically intact but stopped functioning properly after exposure. ## Summary Strategy For your specific situation, I'd recommend: 1. **Start with the easier fix:** Thoroughly clean both the cable and connector contacts with high-percentage isopropyl alcohol 2. **Test cable seating:** Experiment with slight variations in insertion depth and angle while testing keyboard function 3. **Map the failures:** Document which keys don't work to identify affected traces using the keyboard matrix structure 4. **Multimeter testing:** Test continuity from the connector end along suspected traces, repositioning probes as needed for long traces 5. **Assess repair viability:** If you locate specific broken traces accessible near the connector end, consider conductive pen repair; otherwise, replacement is more practical Given that flexible membrane keyboards are notoriously difficult to repair permanently and replacement keyboards for most laptop models are available for \$20-60, weigh the time investment against replacement cost.[^2_4][^2_1] <span style="display:none">[^2_22][^2_23][^2_24][^2_25][^2_26][^2_27][^2_28][^2_29][^2_30][^2_31][^2_32][^2_33][^2_34][^2_35][^2_36][^2_37][^2_38][^2_39][^2_40][^2_41][^2_42][^2_43][^2_44][^2_45][^2_46][^2_47][^2_48][^2_49][^2_50][^2_51][^2_52][^2_53][^2_54][^2_55][^2_56]</span> <div align="center">⁂</div> [^2_1]: https://www.reddit.com/r/AskElectronics/comments/864chw/how_can_i_repair_a_laptop_keyboard_flat_flex/ [^2_2]: https://www.eevblog.com/forum/repair/conductive-ink-or-flex-glue-to-repair-keyboard/ [^2_3]: https://www.reddit.com/r/AskElectronics/comments/2hjxho/is_there_a_solvent_to_expose_conductive_traces_on/ [^2_4]: https://www.eevblog.com/forum/repair/understand-the-laptop-keyboard-for-repair-purposes/ [^2_5]: https://www.reddit.com/r/AskElectronics/comments/i1ki3b/encountering_some_zif_connector_issues_while/ [^2_6]: https://h30434.www3.hp.com/t5/Notebooks-Archive-Read-Only/keyboard-zif-connector-getting-a-replacement-for-top-black/td-p/1088815 [^2_7]: https://www.youtube.com/watch?v=REz928pgCII [^2_8]: https://www.youtube.com/watch?v=LFXKCfQmcy8 [^2_9]: https://dchspanel.com/how-do-the-membrane-switch-continuity-test/ [^2_10]: https://www.instructables.com/Mapping-the-innards-of-a-keyboard/ [^2_11]: https://www.reddit.com/r/AskElectronics/comments/fl0sks/can_anyone_help_me_get_the_oxidization_off_of/ [^2_12]: https://www.youtube.com/watch?v=xqsn0ZtFYbs [^2_13]: https://gennexcorp.com/test-pogo-pins-ultimate-guide/ [^2_14]: https://www.protoexpress.com/blog/how-flying-probe-testing-works-for-pcb-assembly/ [^2_15]: https://www.fixturfab.com/articles/test-fixture-signal-interfaces [^2_16]: http://www.laptoprepair101.com/fix-broken-keyboard-connector-on-laptop-motherboard/ [^2_17]: https://www.reddit.com/r/retrocomputing/comments/14s1zwp/conductive_ink_for_keyboard_membrane/ [^2_18]: https://www.reddit.com/r/AskElectronics/comments/yz7j2x/fixing_a_trace_printed_on_plastic/ [^2_19]: https://www.meetion.com/a-how-to-fix-water-damaged-mechanical-keyboard.html [^2_20]: https://www.linkedin.com/advice/0/how-does-spilled-water-affect-mechanical-wahpc [^2_21]: https://www.facebook.com/groups/ElectronicParts/posts/2667395773449741/ [^2_22]: https://www.ifixit.com/Answers/View/843432/Broken+flex+keyboard+dont+Work [^2_23]: https://www.reddit.com/r/AskElectronics/comments/18ujqk8/is_it_possible_to_fix_this_without_conductive/ [^2_24]: https://www.youtube.com/watch?v=KktvIMT9VuY [^2_25]: https://www.youtube.com/watch?v=XInxW0YtghY [^2_26]: https://www.youtube.com/watch?v=ULwU7U9sIpg [^2_27]: https://www.edaboard.com/threads/how-to-detect-whether-matrix-keypad-is-connected-or-not.356195/ [^2_28]: https://www.facebook.com/groups/ElectronicParts/posts/2686484074874244/ [^2_29]: https://www.youtube.com/watch?v=VBCxo0VHAFU [^2_30]: https://geekhack.org/index.php?topic=9653.0 [^2_31]: https://antiqueradios.com/forums/viewtopic.php?t=354782 [^2_32]: https://www.facebook.com/groups/735824034641967/posts/1063335221890845/ [^2_33]: https://forum.vcfed.org/index.php?threads%2Fhow-to-repair-thin-conductive-keyboard-trace.67268%2Fpage-2 [^2_34]: https://www.eevblog.com/forum/repair/repairing-keyboard-flexible-membrane/ [^2_35]: https://www.reddit.com/r/MechanicalKeyboards/comments/syilb0/rant_get_a_multimeter_people/ [^2_36]: https://www.ifixit.com/Answers/View/504870/Troubleshooting+the+keyboard+ffc-zif+connector [^2_37]: https://www.youtube.com/watch?v=jCjAF7NcsvE [^2_38]: https://www.youtube.com/watch?v=PSJCOKU7noY [^2_39]: https://www.youtube.com/watch?v=HN_xr2Di020 [^2_40]: https://promaxpogopin.com/professional/how-to-clean-lcd-connectors/ [^2_41]: https://www.ifixit.com/Guide/Replacing+a+ZIF+Connector+Locking+Flap/153175 [^2_42]: https://www.instructables.com/Fix-Membrane-Keyboard-With-Some-Non-working-Keys/ [^2_43]: https://www.eevblog.com/forum/repair/ffc-stripping-single-or-both-sides/ [^2_44]: https://www.elecrow.com/blog/how-to-efficiently-perform-a-mechanical-keyboard-test.html [^2_45]: https://bchtechnologies.com/blogs/questions-and-answers/is-ink-on-your-ffc-cable-a-sign-of-damage-tips-for-cleaning-and-repair [^2_46]: https://bobistheoilguy.com/forums/threads/zif-connector-for-a-laptop-keyboard.151173/ [^2_47]: https://www.reddit.com/r/MechanicalKeyboards/comments/uf7su5/are_mechanical_keyboards_more_susceptible_to/ [^2_48]: https://www.sunrom.com/c/test-probes [^2_49]: https://www.groupepace.com/itm/0-7ml-PCB-Keyboard-Repair-With-High-Conductivity/851347 [^2_50]: https://www.adafruit.com/category/634 [^2_51]: https://hirosarts.com/blog/how-to-fix-water-damaged-keyboards/ [^2_52]: https://www.youtube.com/watch?v=rBRmWCPeGQA [^2_53]: https://ptr.ptr-hartmann.com/en/testing-technology/test-probes/ [^2_54]: https://www.ifixit.com/Answers/View/370484/Water+damage-corrosion+on+keyboard+cable+and+cable+connector. [^2_55]: https://www.ebay.com/itm/388108174270 [^2_56]: https://ingun.com/en-US/products/test-probes/ --- How can I connect a multimeter to pcb traces or a flexible cable? Now, the plastic front of the keyboard connects to the metal back via these welded plastic rivets — a bit of plastic goes through a hole in the metal and is then melted on the other side to maintain a tight permanent closure. In order to inspect a keyboard I ripped one of these open, but it was quite destructive, bending the metal frame and breaking the plastic surrounding the keys. What is the correct way to remove such plastic rivets? # Connecting Test Equipment to Keyboard Circuits and Removing Plastic Rivets ## Connecting a Multimeter to PCB Traces and Flexible Cables Testing keyboard circuits requires making reliable electrical contact with delicate conductive surfaces. Here are your practical options: ### For Rigid PCB Traces **Standard multimeter probes** work well on exposed PCB traces and component pads. The key is ensuring good contact:[^3_1][^3_2] - **Direct probing:** Place probe tips directly on exposed copper traces, component pads, or test points[^3_1] - **Alligator clips:** For hands-free testing, clip to larger solder joints or exposed traces. The standard 4mm banana plug connection on most multimeters accepts various clip attachments[^3_2][^3_3] - **Pogo pin probes:** Spring-loaded pogo pin test probes (available with banana plug connections) maintain constant pressure on test points for more consistent readings, especially useful for small high-density circuits. These typically cost \$20-50 for a set[^3_4][^3_5] **Aluminum foil technique for trace following:** Wrap aluminum foil around one finger and connect it to a multimeter probe with a wire and alligator clip. This creates a large contact area that lets you sweep across multiple solder joints quickly. When the multimeter beeps (continuity mode), you've found a connection.[^3_2] ### For Flexible Cable Contacts Flexible flat cable (FFC) contacts present a challenge since they're often recessed inside connectors. Your options: **Option 1: Test at the connector pads** The gold-plated contact pads where the cable enters its connector are your most accessible test points. These provide solid surfaces for standard probes.[^3_6][^3_7] **Option 2: Pogo pin contact** For repeated testing of flex cable contacts, spring-loaded pogo pins with appropriate extension force (10-30 grams for standard applications) can make reliable temporary contact without damage. However, positioning them accurately requires either:[^3_8][^3_4] - A custom test fixture (impractical for one-off repairs)[^3_4][^3_8] - Manual pressure holding the pin against the contact point[^3_5] **Option 3: Wire shorting for diagnostic testing** To test if specific keys work, temporarily short connector contact pads with a thin wire or paper clip. This simulates a key press and confirms whether the issue is in the membrane or the cable/connector.[^3_7] **Option 4: Flexible back probes** Flexible silicone-insulated probes designed for automotive connector testing can reach tight spaces and bend around obstacles. These have 4mm banana plug connections and work up to 30V. While designed for automotive work, they're useful for accessing recessed keyboard connector pins.[^3_9] ### For Membrane Keyboard Traces The conductive ink traces on flexible plastic membranes are nearly impossible to probe directly without damage. **Your best approach is testing at the ends** where traces terminate at the connector contacts, using the methods above.[^3_10][^3_11] If you must test along a trace's length, conductive epoxy or tape can temporarily attach a fine wire to the trace surface, but this risks damaging the delicate conductive layer.[^3_11] ### Practical Testing Setup For keyboard diagnosis specifically: 1. **Set multimeter to continuity mode** (beeps when resistance <70Ω)[^3_12][^3_13] 2. **Clip the common (black) probe** to one connector pad using an alligator clip for hands-free operation[^3_2] 3. **Use the red probe** to test other pads, key contact points, or trace continuity[^3_13][^3_14] 4. **For long traces:** Reposition your common probe closer if you don't get a beep—trace resistance over long distances may exceed the continuity threshold[^3_12] ## Removing Plastic Rivets from Keyboards The melted plastic rivets (also called ultrasonic-welded rivets or staked rivets) holding laptop keyboards are designed to be permanent. Your destructive experience is common—most people damage the assembly on first attempts. Here's the correct approach:[^3_15][^3_16][^3_17] ### The Proper Removal Method **Tools needed:** - Rotary tool (Dremel or similar) with small grinding stone attachment - OR a sharp utility knife (harder, slower, higher skill requirement) - Patience and steady hands[^3_18][^3_15] **Step-by-step process:** 1. **Grind down the rivet crowns** (the mushroom-shaped heads on top):[^3_19][^3_15][^3_18] - Use a small grinding stone on your rotary tool - Carefully grind each rivet crown until it's **flush with the metal backplate surface**[^3_15] - The goal is to remove only the crown while preserving as much of the rivet shaft as possible[^3_18][^3_15] - **Critical:** Don't grind too deep—you want to keep the plastic shaft that goes through the hole intact[^3_15] 2. **Check your work frequently:** Stop grinding periodically to check if the crown is flush. Over-grinding wastes the rivet material you'll need for reassembly.[^3_15] 3. **Remove the backplate gently:** - Place your fingers under the keyboard from beneath - Push upward gently and evenly[^3_15] - If you feel significant resistance, you missed a rivet—find it and grind it down[^3_15] - **Never pry or twist** the metal plate, as this causes the bending and warping you experienced[^3_15] ### Why Your Method Caused Damage Ripping or prying plastic rivets causes: - **Metal backplate bending** from leverage forces[^3_20][^3_15] - **Plastic frame cracking** around the rivet holes from stress concentration[^3_21][^3_15] - **Loss of rivet material** needed for reassembly[^3_18][^3_15] The grinding method avoids these issues by removing only the retaining crown while preserving the shaft.[^3_18][^3_15] ### Reassembly: Creating New Rivets Once you've replaced the faulty keyboard, you need to recreate the rivets. The professional method uses **melted zip tie plastic**:[^3_22][^3_15] **Materials:** - Black plastic zip ties (cable ties) - Soldering iron or hot knife (cheap tool recommended—the tip will be sacrificed)[^3_21][^3_15] - OR hot air rework station[^3_22] **Process:** 1. **Cut thin strips from zip ties** if using wide ones[^3_15] 2. **Position the new keyboard and backplate** in place[^3_15] 3. **For each rivet location:** - Place the zip tie strip over the original rivet shaft[^3_15] - Heat with soldering iron to melt both the zip tie and the original rivet plastic[^3_21][^3_15] - **Push down firmly** while simultaneously **pressing the backplate from below** to sandwich everything together[^3_15] - The molten plastics will fuse into a single unit[^3_15] - Hold pressure while blowing on it to cool (about 10-15 seconds)[^3_15] **Why zip ties work:** Zip ties are thermoplastic, and when melted alongside the original rivet plastic, they fuse chemically rather than just adhering adhesively. This creates a bond as strong as the original manufacturing weld.[^3_16][^3_15] **Alternative for edges:** For rivets near keyboard edges where the grinding tool won't fit, small flat cutters can carefully shear off the crown. You need a delicate touch—too much force cuts through the shaft entirely.[^3_19] ### Alternative Tools **Upholstery tack remover:** Some technicians use upholstery tack removal tools designed for removing furniture tacks. These work well on the main keyboard area but struggle with edge rivets where they can't sit flat.[^3_19] **Hot air method for softening (not removal):** Some people use hot air rework stations to soften rivets for removal, but this is finicky and risks melting the plastic frame itself. It's not recommended compared to the grinding method.[^3_20][^3_22] ### Why Keyboards Are Riveted This Way Ultrasonic welding/riveting is a manufacturing process where ultrasonic vibration melts thermoplastic at specific points, creating permanent joints. It's:[^3_23][^3_24][^3_25][^3_16] - **Fast** (seconds per rivet)[^3_26] - **Strong** (equivalent to the base material strength)[^3_24][^3_23] - **Cost-effective** for mass production[^3_24] - **Clean** (no adhesives, no fasteners)[^3_24] Unfortunately, these advantages make keyboards difficult to service.[^3_17][^3_15] ### Time Investment Expect **3-4 hours minimum** for a complete keyboard replacement using this method:[^3_15] - Disassembly: 30-60 minutes - Grinding all rivets: 60-90 minutes - Reassembly and re-riveting: 60-90 minutes - Testing and final assembly: 30 minutes The first time takes longer. With practice, you can reduce this time.[^3_15] ### When to Consider Alternatives Given the difficulty and time investment, many technicians recommend: - **Replace the entire palm rest/top case assembly** if the keyboard is riveted (costs \$30-80 depending on laptop model)[^3_27][^3_15] - **Only attempt rivet removal/replacement** if you can't source the complete assembly or want to preserve original parts[^3_15] ## Summary Recommendation For testing, start with standard multimeter probes and alligator clips at the connector contact points—this covers 90% of keyboard diagnostics. For rivet removal, invest in a basic rotary tool with grinding stones if you don't already have one, and budget several hours for careful, patient work. The zip tie fusion method for reassembly is proven effective and creates durable repairs comparable to factory assembly.[^3_28][^3_15] <span style="display:none">[^3_29][^3_30][^3_31][^3_32][^3_33][^3_34][^3_35][^3_36][^3_37][^3_38][^3_39][^3_40][^3_41][^3_42][^3_43][^3_44][^3_45][^3_46][^3_47][^3_48]</span> <div align="center">⁂</div> [^3_1]: https://resources.altium.com/p/pcb-design-test-test-structures-and-types-tests-part-1 [^3_2]: https://www.instructables.com/How-To-Quickly-Find-And-Trace-PCB-Tracks-1/ [^3_3]: https://www.fluke.com/en-us/products/accessories/test-leads [^3_4]: https://gennexcorp.com/test-pogo-pins-ultimate-guide/ [^3_5]: https://www.testequity.com/product/35704-1-6342 [^3_6]: https://www.instructables.com/Mapping-the-innards-of-a-keyboard/ [^3_7]: https://www.reddit.com/r/AskElectronics/comments/2hjxho/is_there_a_solvent_to_expose_conductive_traces_on/ [^3_8]: https://www.fixturfab.com/articles/test-fixture-signal-interfaces [^3_9]: https://www.lislecorp.com/specialty-tools/flexible-back-probes-4pc [^3_10]: https://www.eevblog.com/forum/repair/understand-the-laptop-keyboard-for-repair-purposes/ [^3_11]: https://www.reddit.com/r/AskElectronics/comments/yz7j2x/fixing_a_trace_printed_on_plastic/ [^3_12]: https://www.youtube.com/watch?v=REz928pgCII [^3_13]: https://www.youtube.com/watch?v=LFXKCfQmcy8 [^3_14]: https://dchspanel.com/how-do-the-membrane-switch-continuity-test/ [^3_15]: https://www.youtube.com/watch?v=YIJ-1oTwb48 [^3_16]: https://www.keber.cn/us/wap/content/?778.html [^3_17]: https://www.reddit.com/r/diyelectronics/comments/mmctv9/so_i_took_apart_my_entire_laptop_to_replace_the/ [^3_18]: https://www.youtube.com/watch?v=KZo-W6yzsGQ [^3_19]: https://www.youtube.com/watch?v=JDLg5QF6QeA [^3_20]: https://groupdiy.com/threads/hot-riveted-plastic-clips-how-to-uninstall-and-reinstall.84489/ [^3_21]: https://www.youtube.com/watch?v=r1IP7VC-gwU [^3_22]: https://www.reddit.com/r/Tools/comments/152k3g9/reforming_small_plastic_rivets/ [^3_23]: https://www.assemblymag.com/articles/98726-ultrasonic-extruded-weld-riveting [^3_24]: https://sonotronic.de/en/technologies/ultrasonic/ultrasonic-riveting/ [^3_25]: https://www.youtube.com/watch?v=qo8zq_c-FiI [^3_26]: https://documents.dukane.com/DesignGuides/Guide To US Plastic Assembly.pdf [^3_27]: https://www.reddit.com/r/AskElectronics/comments/864chw/how_can_i_repair_a_laptop_keyboard_flat_flex/ [^3_28]: https://www.reddit.com/r/modelm/comments/w6burc/is_it_possible_to_reweld_the_plastic_rivets_on/ [^3_29]: https://www.youtube.com/watch?v=HxeKfwPD-3k [^3_30]: https://www.technibble.com/forums/threads/replacing-riveted-laptop-kboards.90107/ [^3_31]: https://www.facebook.com/groups/subarumechanics/posts/3695724384050153/ [^3_32]: https://www.walmart.com/c/kp/plastic-rivets-removal-tool [^3_33]: https://www.tiktok.com/@roadkill.garage/video/7384972083719130411 [^3_34]: https://sktools.com/products/body-clip-and-rivet-removal-set [^3_35]: https://www.youtube.com/watch?v=oxPD6QdwkvQ [^3_36]: https://www.youtube.com/watch?v=eTqYbIHjK9s [^3_37]: https://www.protoexpress.com/blog/how-flying-probe-testing-works-for-pcb-assembly/ [^3_38]: https://ptr.ptr-hartmann.com/en/testing-technology/test-probes/ [^3_39]: https://hackaday.com/2025/01/27/diy-probe-clamps-to-ease-your-pcb-work/ [^3_40]: https://probemaster.com/dmm-multimeter-test-leads/ [^3_41]: https://www.keyelco.com/category.cfm/Keyelco/Test-Points-Tips-Probes-Clips/id/518 [^3_42]: https://www.ccpcontactprobes.com/sites/default/files/2021-08/CCP_Contact_Probes_Company_Presentation_20210827_330ppi_0.pdf [^3_43]: https://www.ebay.com/itm/277394758381 [^3_44]: https://www.youtube.com/watch?v=MiA78HjaIEg [^3_45]: https://ingun.com/en-US/products/test-probes/ [^3_46]: https://www.homedepot.com/p/Lukyamzn-27-Piece-Multimeter-Test-Leads-Probes-Kit-with-Alligator-Clips-Test-Tweezers-Flexible-Electrical-Accessories-PH03327B536/337048686 [^3_47]: https://learn.sparkfun.com/tutorials/how-to-work-with-jumper-pads-and-pcb-traces/all [^3_48]: https://www.adafruit.com/category/634 --- Great rivet information if it works. Can you again clarify how to test _very tiny laptop keyboard connector leads_? When I was young I would solder needles to my multimeters but my hands shake now. # Testing Very Tiny Laptop Keyboard Connector Leads Given your shaky hands, here are practical solutions that eliminate the need to hold probes steady while testing those delicate keyboard flex cable contacts: ## Spring-Loaded Fine-Pitch Probes The modern solution to your needle-soldering approach is **spring-loaded needle probe tips**. These are specifically designed for SMD (surface mount device) testing and maintain contact pressure without requiring steady hands.[^4_1][^4_2][^4_3] **Best options:** **ProbeMS 9110 SMD Spring Tip Micro Probe Kit** (\$50-80):[^4_1] - Spring-loaded sharp needle tip (0.013" diameter)[^4_1] - The spring mechanism keeps constant pressure even if your hand shakes[^4_1] - Gold-plated contacts for reliability[^4_1] - Fits standard 4mm banana plug multimeters (Fluke, etc.)[^4_1] - Includes multiple tip sizes: 0.025", 0.030", 0.040"[^4_3][^4_1] **Tag-Connect Non-Slip Probe Tips** (\$30):[^4_2] - Tungsten carbide tips with machined flutes that "bite" into surfaces[^4_2] - Available in 0.6mm (fine) and 0.8mm (standard) sizes[^4_2] - Slide onto your existing 2mm multimeter probes[^4_2] - The fluted design prevents slipping even with unsteady hands[^4_2] **SparkFun/Generic Needle-Tipped Probes** (\$7-15):[^4_4][^4_5] - Basic sharp needle tips (0.7mm)[^4_4] - 36" lead length gives flexibility[^4_5] - Budget option, though without spring-loading[^4_5] The **spring-loaded versions are crucial** for your situation—the spring compensates for hand tremor by maintaining consistent pressure.[^4_6][^4_3][^4_1] ## Hands-Free Probe Holders (The Real Solution) Rather than holding probes at all, use positioning systems that clamp probes in place. This is the approach professional technicians use for fine-pitch work: ### PCBite System (Premium, \$150-250) The **PCBite** from Sensepeek is specifically designed for hands-free probing of dense electronics:[^4_7][^4_8][^4_9][^4_10][^4_11][^4_12] **How it works:** - Steel magnetic base plate that sits flat on your bench[^4_8][^4_12][^4_7] - Magnetic probe holders with flexible arms and weighted heads[^4_12][^4_7][^4_8] - Spring-loaded pogo pin probes in the tips[^4_9][^4_8][^4_12] - You position the probe needle once, then let go—it stays put via magnetism and gravity[^4_13][^4_7][^4_8] **Key advantages for shaky hands:** - "Lift and drop" positioning—no set screws or fine adjustments needed[^4_7] - The weighted probe head maintains constant needle pressure even if you bump the table[^4_8][^4_7] - Magnetic base means you can quickly reposition without tools[^4_12][^4_8] - Probes have dual-pin headers (0.1"/2.54mm spacing) that connect directly to multimeter test leads via Dupont wires[^4_9][^4_8][^4_12] **SP10 probe specifications:** - Fine needle tips for dense circuits[^4_9][^4_12] - Fits test points and component leads down to 0.5mm pitch[^4_9] - Four probes included in standard kit[^4_8][^4_12] **Downsides:** - Expensive (\$150-250 for complete kit)[^4_10][^4_12][^4_8] - Probes can be knocked over by cable snags[^4_11] - Requires space for the steel base plate[^4_11] ### DIY Magnetic Base Holders (Budget, \$20-50) You can build your own probe holder system using parts:[^4_14][^4_15][^4_16] **Components needed:** - **Dial indicator magnetic base** (\$15-30 from machinist tool suppliers)[^4_16] - These have a magnetic base with an on/off switch[^4_16] - Articulating arm with ball joints[^4_16] - Some models include fine micrometer adjustment[^4_16] - **Spring-loaded needle probes** (\$10-20)[^4_5][^4_1] - Attach to the articulating arm - Wire them to banana plug connectors for your multimeter **Assembly approach:** One DIYer created a custom PCB with pogo pins that connects to the magnetic arm, with header connectors for test equipment. The magnetic base holds it steady, and you position it once then connect your multimeter to the headers.[^4_14] ### Third-Hand Tools with Probe Attachments (\$15-60) Traditional "helping hands" tools now have versions suitable for probe holding:[^4_15][^4_17][^4_18] **SparkFun Third Hand Kit** (\$38):[^4_17] - Heavy aluminum base (prevents tipping)[^4_17] - Two flexible arms with multiple articulation points[^4_17] - Originally designed for alligator clips, but you can attach probes instead[^4_17] **Generic flexible gooseneck third hands** (\$15-30):[^4_18][^4_19] - Multiple flexible arms (4-6 typically)[^4_19] - Ball-joint construction[^4_19] - Weighted base[^4_18][^4_19] **How to adapt for probe holding:** Attach your spring-loaded needle probes to the clips using small zip ties or by replacing the alligator clips with custom mounts.[^4_20][^4_15] ## Practical Testing Workflow for Keyboard Connectors Here's how to combine these tools for your specific laptop keyboard situation: ### Setup Method 1: PCBite System 1. Place steel base plate under your workspace 2. Position keyboard with flex cable accessible 3. Attach PCBite holders to secure the keyboard frame 4. Position SP10 probes on individual flex cable contacts 5. Connect Dupont wires from probe headers to multimeter leads 6. Test continuity hands-free[^4_12][^4_8][^4_9] ### Setup Method 2: DIY Magnetic Base 1. Position magnetic base on metal surface near keyboard 2. Attach spring-loaded needle probe to articulating arm 3. Fine-adjust probe position onto one flex cable contact 4. Lock magnetic base switch to hold position 5. Connect probe's banana plug to multimeter common (black) lead 6. Use handheld red probe to test other contacts[^4_16] ### Setup Method 3: Solder Temporary Wires (Your Current Best Option) For laptop keyboards specifically, where contacts are often recessed and difficult to probe: 1. **Use 30 AWG or 32 AWG magnet wire** (enameled wire)[^4_21][^4_22][^4_10] 2. **Tack solder a 2-3 inch wire to each contact** you need to test[^4_21][^4_10] 3. The thin wire won't stress the delicate traces[^4_10][^4_21] 4. Route wires to a more convenient location where you can clip alligator clips[^4_21] 5. Test with multimeter via the wires hands-free[^4_21] This is what professionals do when probe access is impossible.[^4_22][^4_10][^4_21] ### Setup Method 4: Test Point PCB Adapter (Advanced) Create a custom PCB with pogo pins matching your connector spacing, with those pins wired to 0.1" header pins. You press this adapter onto the flex cable contacts once, then connect test equipment to the convenient headers.[^4_16] ## Specific Recommendations for Your Situation Given your: - Hand tremor - Need to test tiny (sub-1mm) flex cable contacts - Budget concerns (likely) **Immediate solution (under \$30):** - Buy spring-loaded SMD needle probes (\$7-20)[^4_5][^4_1] - Buy a dial indicator magnetic base (\$15-30)[^4_16] - Attach probe to magnetic arm - Use magnetic positioning to hold probe steady **Long-term solution (if you repair keyboards often):** - Invest in PCBite kit (\$150-250)[^4_8][^4_12] - The hands-free operation and rapid repositioning will save enormous frustration - Multiple keyboards can be tested efficiently **For specific keyboard connector testing right now:** - Solder thin magnet wire (30-32 AWG) to critical contacts[^4_22][^4_21] - This creates stable test points you can clip to with standard alligator clips - Removes the need for steady probe positioning entirely ## Additional Stabilization Tip If using handheld probes at all, **rest your hand on the work surface**. Brace your wrist or forearm against a solid surface to create a stable pivot point. This dramatically reduces the effect of hand tremor—the movement becomes rotational around your wrist rather than translational.[^4_22] The key insight: **modern electronics testing has moved away from handheld probing** for exactly the reasons you're experiencing. Spring-loaded tips and magnetic holder systems are now standard in professional settings specifically because they eliminate the need for steady hands while improving reliability.[^4_7][^4_8][^4_1][^4_16] <span style="display:none">[^4_23][^4_24][^4_25][^4_26][^4_27][^4_28][^4_29][^4_30][^4_31][^4_32][^4_33][^4_34][^4_35][^4_36][^4_37][^4_38][^4_39]</span> <div align="center">⁂</div> [^4_1]: https://probemaster.com/9110-smd-spring-tip-micro-probe-deluxe-kit/ [^4_2]: https://www.tag-connect.com/product/non-slip-probe-tips [^4_3]: https://probemaster.com/smd-grippers-test-clips/ [^4_4]: https://www.robotics.org.za/RB-NEEDLE [^4_5]: https://www.sparkfun.com/multimeter-probes-needle-tipped.html [^4_6]: https://prc.keysight.com/Content/PDF_Files/N2879-97000.pdf [^4_7]: https://acutena.com/en-can/products/pcbite-kit-with-2x-sq-mhz-handsfree-oscilloscope-probes [^4_8]: https://sensepeek.com/pcbite-20 [^4_9]: https://sensepeek.com/pcbite-probes [^4_10]: https://www.reddit.com/r/embedded/comments/1n9aq5g/what_tool_do_you_use_to_probe_pins_on_pcb_without/ [^4_11]: https://www.eevblog.com/forum/reviews/pcbite-is-a-brilliant-oscilloscope-probe-holder/ [^4_12]: https://binho.io/products/pcbite-kit-with-4x-sp10-probes-and-test-wires [^4_13]: https://www.youtube.com/watch?v=EGIDVK14--c [^4_14]: https://www.youtube.com/watch?v=MiA78HjaIEg [^4_15]: https://makezine.com/projects/3d-print-the-ultimate-helping-hands-for-a-pcb-workstation/ [^4_16]: https://www.eevblog.com/forum/testgear/i-need-a-better-(cheap)-probe-for-measuring-signals-on-arbitrary-devicespcbs/ [^4_17]: https://www.sparkfun.com/sparkfun-third-hand-kit.html [^4_18]: https://snakeclamp.com/collections/third-hand-tools [^4_19]: https://tinkersphere.com/helping-hands-vises/2397-flexible-third-hand-kit-with-6-arms.html [^4_20]: https://www.engineerable.com/single-post/diy-the-best-helping-hands-for-electronics-soldering-pcb-work-jewelry [^4_21]: https://www.reddit.com/r/AskElectronics/comments/1i6260t/tips_on_probing_fine_pitch_surface_mount_devices/ [^4_22]: https://www.reddit.com/r/AskElectronics/comments/b4a6bf/need_to_probe_an_ultra_small_ic_what_tools_do_you/ [^4_23]: https://www.keysight.com/us/en/product/N2879A/fine-pitch-passive-probe-accessory-kit.html [^4_24]: https://www.newark.com/c/test-measurement/test-leads-test-probes/test-probes-lead-end-connectors [^4_25]: https://www.eevblog.com/forum/projects/fixturingmechanisms-for-postitioning-and-holding-probes-soldering-irons-etc/ [^4_26]: https://www.fluke.com/en-us/products/accessories/test-leads [^4_27]: https://www.reddit.com/r/diypedals/comments/mclbmx/best_pcb_holderhelping_hands_device/ [^4_28]: https://www.pomonaelectronics.com/products/dmm-test-leads-and-probes/test-leads-and-probes [^4_29]: https://www.eevblog.com/forum/testgear/test-clipsgrabbers-for-fine-pitch-ics/ [^4_30]: https://probemaster.com/dmm-multimeter-test-leads/ [^4_31]: https://www.thingiverse.com/thing:6455809 [^4_32]: https://www.ebay.com/b/Third-Hand-Tool/46413/bn_7022293347 [^4_33]: https://www.sainsmart.com/collections/soldering/soldering-accessories [^4_34]: https://sensepeek.com/pcbite-kit-with-4x-sq10-probes-and-test-wires [^4_35]: https://www.printables.com/search/models?q=tag%3Athirdhand [^4_36]: https://www.ebay.com/itm/197750765994 [^4_37]: https://legacy.cttc.co/sites/default/files/marketing_projects_attachments/MKT13143.pdf [^4_38]: https://sensepeek.com [^4_39]: https://www.walmart.com/c/kp/third-hand-holder --- Great information! Now, a slightly different focus, it could be nice to set myself up so I can solve almost any electronic problem with appropriate tools like an oscilloscope, which I usually don’t budget for. Most of my stuff is broken right now (pinephone, ttl prototype, laptops), but I’ve used up early most of my money for the month. Is there something super cheap I could buy to e.g. help me figure out if the pinephone is the display cable or the mainboard or what? I imagine trying each pin with an oscilloscope during boot, but maybe that’s overkill. Something under $30? # Budget Diagnostic Tool for Multiple Electronics Repairs Under \$30 For your situation—multiple broken devices (Pinephone, TTL prototype, laptops) and limited budget—here's what will give you the most diagnostic power: ## The Best Sub-\$30 Option: USB Logic Analyzer (\$8-15) **A cheap 8-channel USB logic analyzer** is your most versatile diagnostic tool under \$30.[^5_1][^5_2][^5_3][^5_4] ### What You Get **Hardware specs:** - 8 channels (can monitor 8 signals simultaneously)[^5_3][^5_1] - 24MHz sample rate[^5_4][^5_1][^5_3] - Effective signal detection up to ~2-6MHz[^5_3] - Works with free sigrok/PulseView software[^5_1] - USB powered—no external power needed[^5_1] **Where to buy:** - AliExpress/Amazon: \$5-15[^5_2][^5_4][^5_3] - SparkFun official version (TOL-18627): ~\$20[^5_1] ### Why This Over an Oscilloscope **For digital circuits** (which describes all your broken devices), a logic analyzer is often **more useful than an oscilloscope**:[^5_5][^5_6][^5_2] 1. **Multiple signals at once:** You can see 8 different pins/signals simultaneously. An oscilloscope shows only 2-4 channels and costs \$60-200 for entry-level models[^5_7][^5_2][^5_3][^5_1] 2. **Protocol decoding:** The software automatically decodes I2C, SPI, UART, and other digital protocols. This is **huge** for diagnosing communication issues between chips[^5_6][^5_8][^5_4][^5_1] 3. **Perfect for boot diagnosis:** You can connect to multiple signals (power rails, enable pins, clock lines, data buses) and see the exact sequence of what happens during power-on[^5_8][^5_6] 4. **Time correlation:** See how different signals relate to each other in time—essential for understanding why something doesn't initialize[^5_6][^5_1] ### What It Can't Do - **Can't measure analog voltages accurately** (but you have a multimeter for that)[^5_9][^5_2][^5_6] - **Not great above 6MHz reliably** on the \$8 versions (the 24MHz spec is sample rate, not maximum signal frequency)[^5_3] - **Small buffer** means you can only capture short time windows (typically milliseconds)[^5_3] ### Practical Application to Your Devices #### For the Pinephone Display Issue **Common Pinephone display symptoms:** - Black screen with backlight = likely loose display cable or failed display panel[^5_10][^5_11][^5_12] - Flickering = loose cable connection[^5_13][^5_12] - No backlight = power rail issue or cable[^5_10] **Diagnostic approach without oscilloscope:** **1. Start with physical inspection** (free):[^5_11][^5_14][^5_10] - Open the phone (easier than laptop keyboards)[^5_14] - Check if display flex cable is seated properly in connector[^5_12][^5_11][^5_10] - Press along screen edges while powered—if display changes, it's the cable[^5_12] - Reseat the cable[^5_11][^5_10] **2. Multimeter testing** (you already have this): - Check battery voltage (should be 3.7-4.2V for Li-ion)[^5_11] - Check backlight power rail at connector (typically 3.3V or 5V)[^5_12] - Continuity test on display cable if it appears damaged[^5_15][^5_16][^5_12] **3. Logic analyzer use case** (if you had one): - Monitor the display interface signals (MIPI DSI or similar)[^5_10] - See if the phone is **sending** display data during boot[^5_10] - If data is present but no display, it's the panel or cable[^5_10] - If no data is sent, it's a mainboard/software issue[^5_10] **However:** For Pinephone specifically, **you probably don't need a logic analyzer**. The most common failure mode is the display cable itself, which you diagnose by:[^5_11][^5_10] - Physical inspection - Reseating - Swapping the display/cable (replacement parts are available from Pine64)[^5_14] #### For TTL Prototype and Laptop Issues **The logic analyzer is most valuable here**:[^5_17][^5_2][^5_4] **TTL circuits:** - Monitor clock signals, data buses, chip select lines simultaneously[^5_4][^5_17] - Identify timing problems that a multimeter can't see[^5_4][^5_6] - Debug which IC isn't responding[^5_17] **Laptop diagnostics:** - Monitor power sequencing during boot - Check if peripherals are responding on I2C/SPI buses - See if keyboard controller is sending scan codes ### Specific Product Recommendations **Budget tier (\$8-15):** - Generic "Saleae clone" 8-channel 24MHz from AliExpress[^5_18][^5_2][^5_4][^5_3] - Search terms: "USB logic analyzer 24MHz 8 channel"[^5_18] - Works with free sigrok PulseView software[^5_1] - **Caveat:** Quality control is variable; USB buffering can cause glitches on fast signals[^5_3] **Quality budget tier (\$20-30):** - SparkFun Logic Analyzer (TOL-18627) - \$20[^5_1] - Official hardware, better QC, same software compatibility[^5_1] - DSLogic U2 Basic - \$25-30 (if you can find it)[^5_19][^5_2] ### Alternative Under \$30: Hantek/OWON USB Oscilloscope (\$50-80... wait, too expensive) I was going to recommend the **OWON VDS1022** USB oscilloscope (\$50-60), but that's over your \$30 budget. However, **if you can stretch** to \$50-60:[^5_2][^5_7] - 2-channel, 25MHz bandwidth[^5_7][^5_2] - Better than logic analyzers for analog signals and power rail troubleshooting[^5_7] - Can measure voltage waveforms, see noise, detect ripple[^5_7] - "Vastly superior" to the cheaper Hantek 6022BE[^5_2] **But honestly:** At your \$30 budget, the logic analyzer + your existing multimeter is the right combo.[^5_17][^5_2] ### The Absolute Cheapest Option: Just Use Your Multimeter Better If you can't spend anything right now: **For the Pinephone:** 1. **Open it** and reseat the display cable[^5_14][^5_11][^5_10] 2. **Multimeter continuity test** on the cable if it looks damaged[^5_16][^5_15][^5_12] 3. **Test voltage** at display connector pins while powered[^5_12] 4. **Replace the cable** if damaged (Pine64 sells replacements cheap)[^5_14] **For laptops:** 1. **Voltage testing** at power rails[^5_15] 2. **Continuity testing** on keyboard matrix traces (as we discussed)[^5_16][^5_15] 3. **Visual inspection** for burned components, broken traces[^5_20] **For TTL prototype:** 1. **Power rail testing** first—most issues are power-related[^5_17] 2. **Pin-by-pin voltage checks** on ICs to see what's powered[^5_20][^5_17] 3. **Continuity testing** on connections[^5_15][^5_16] **Truth from the forums:** Many people successfully troubleshoot Ben Eater's 8-bit computer (complex TTL project) using **only a multimeter and logic probe** (\$10-15). The logic analyzer is nice but not essential for low-speed digital.[^5_21][^5_17] ### My Recommendation for Your Specific Situation **Immediate action (free-\$5):** 1. **Open the Pinephone** and reseat the display cable[^5_11][^5_10] 2. **Check for obvious physical damage** on all devices[^5_12] 3. **Multimeter voltage and continuity testing** on suspected failure points[^5_15] **If you have \$15-20 to spend:** Buy the **SparkFun USB Logic Analyzer (\$20)**. It will help with the TTL prototype and laptop boot issues, though probably not the Pinephone display.[^5_11][^5_10][^5_1] **If you only have \$8-10:** Buy the **generic 8-channel logic analyzer** from AliExpress. Same functionality, just less reliable quality control.[^5_4][^5_3] **If you can find \$25-30:** Buy the **DSLogic U2 Basic** if available. Better buffer, more reliable capture, still works with free software.[^5_19][^5_2] **Reality check:** For phone display issues specifically, physical cable reseating and replacement is almost always the answer. The logic analyzer won't help much there. But for everything else, especially TTL debugging, it's invaluable.[^5_22][^5_23][^5_4][^5_17][^5_12][^5_1] The \$8 logic analyzer + your existing multimeter will give you diagnostic coverage for probably 90% of electronics troubleshooting scenarios.[^5_8][^5_2][^5_17] <span style="display:none">[^5_24][^5_25][^5_26][^5_27][^5_28][^5_29][^5_30][^5_31][^5_32][^5_33][^5_34][^5_35][^5_36][^5_37][^5_38][^5_39][^5_40]</span> <div align="center">⁂</div> [^5_1]: https://learn.sparkfun.com/tutorials/using-the-usb-logic-analyzer-with-sigrok-pulseview/all [^5_2]: https://www.reddit.com/r/embedded/comments/n8hcoy/what_is_the_best_cheap_oscilloscope_for_embedded/ [^5_3]: https://www.reddit.com/r/embedded/comments/10yyddl/cheap_logic_analyzer_precision/ [^5_4]: https://www.youtube.com/watch?v=2sAJoszsuo8 [^5_5]: https://community.simplefoc.com/t/oscilloscope-or-logic-analyzer/3748 [^5_6]: https://digilent.com/blog/when-is-a-multimeter-not-enough/ [^5_7]: https://www.youtube.com/watch?v=1ec1n9ScGTw [^5_8]: https://www.youtube.com/watch?v=SSp1wn0Abck [^5_9]: https://www.techtownforum.com/knowledge-base/equipment-appliances/tech-tools/logic-probe-vs-multimeter-what-are-the-differences/ [^5_10]: https://forum.pine64.org/showthread.php?tid=19318 [^5_11]: https://www.ifixit.com/Wiki/PinePhone64_Troubleshooting [^5_12]: https://www.linkedin.com/pulse/how-determine-problem-damaged-screen-faulty-flex-cable-jojo-huang-mmfoc [^5_13]: https://forum.pine64.org/showthread.php?tid=18859 [^5_14]: https://pine64.org/documentation/PinePhone/Repairs/ [^5_15]: https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-test-for-continuity [^5_16]: https://www.skillcatapp.com/post/measuring-continuity [^5_17]: https://www.reddit.com/r/beneater/comments/kl058o/bens_8bit_troubleshooting_tools_logic_analyzer/ [^5_18]: https://www.eevblog.com/forum/testgear/best-cheap-knockoff-logic-analyzer/ [^5_19]: https://www.bigmessowires.com/2021/11/21/logic-analyzer-shopping/ [^5_20]: https://www.instructables.com/How-To-Quickly-Find-And-Trace-PCB-Tracks-1/ [^5_21]: https://forum.vcfed.org/index.php?threads%2Flogic-probe-vs-logic-analyser.52919%2F [^5_22]: https://xdaforums.com/t/q-black-screen-loose-cable.2366178/ [^5_23]: https://www.reddit.com/r/mobilerepair/comments/wxa2f5/is_my_screen_connector_loose/ [^5_24]: https://www.eevblog.com/forum/beginners/cheap-logic-analyser/ [^5_25]: https://forum.pine64.org/showthread.php?tid=15076 [^5_26]: https://forum.allaboutcircuits.com/threads/logic-analyzer-purchase.197929/ [^5_27]: https://lisalist2.com/index.php?topic=606.0 [^5_28]: https://hackaday.com/2015/05/26/review-dslogic-logic-analyzer/ [^5_29]: https://www.reddit.com/r/PinePhoneOfficial/comments/zl146y/pinephone_screen_goes_black_after_1_second/ [^5_30]: https://github.com/Tow-Boot/Tow-Boot/issues/278 [^5_31]: https://forum.microchip.com/s/topic/a5C3l000000Mc5MEAS/t376460 [^5_32]: https://www.youtube.com/watch?v=iG0-0R9qYWU [^5_33]: https://cyberraiden.wordpress.com/2025/07/31/signs-of-damaged-displayport-cable-in-the-desktop-computer/ [^5_34]: https://www.wikihow.com/Test-Continuity-with-a-Multimeter [^5_35]: https://www.diyfixtool.com/blogs/news/how-to-use-multimeter-in-mobile-phone-repairing [^5_36]: https://forum.pine64.org/showthread.php?tid=12665 [^5_37]: https://www.youtube.com/watch?v=Ib10TBicCcw [^5_38]: https://www.youtube.com/watch?v=Cev8gsmR_RI [^5_39]: https://forum.allaboutcircuits.com/threads/logic-probe-vs-multimeter.180900/ [^5_40]: https://www.quecoo.com/blogs/mobile-phone-repair/the-complete-guide-to-using-multimeters-in-mobile-phone-repair --- What will I be missing at 6-25MHz? I mean, my laptop cpu is GHz. # What You'll Miss at 6-25MHz (And Why It Usually Doesn't Matter) You're absolutely right that your laptop CPU runs at GHz speeds, but **the signals you actually need to debug run much, much slower**. Here's what's happening at different speeds and what you can/can't capture: ## What the 24MHz Logic Analyzer Can Capture **Common embedded system buses (all well within 24MHz capture):** - **I2C:** 100 kHz (standard), 400 kHz (fast), 1 MHz (fast-mode plus), 3.4 MHz (high-speed)[^6_1][^6_2][^6_3] - **SPI:** Typically 1-20 MHz for embedded systems[^6_2][^6_4][^6_1] - **UART:** 9600 to 460 kbps (0.0096-0.46 MHz)[^6_5][^6_1][^6_2] - **PWM signals:** Most run 1-100 kHz[^6_6] - **GPIO toggling:** Usually <10 MHz for debugging purposes[^6_7] **Real capture limits:** - **Reliable capture up to ~2-6 MHz** on the cheap \$8 analyzers[^6_8][^6_9][^6_6] - You need **4-10x oversampling** for clean digital capture[^6_6] - 24 MHz sample rate ÷ 4x = **6 MHz maximum signal** for reliable decoding[^6_6] - With 10x oversampling: 24 MHz ÷ 10 = **2.4 MHz maximum**[^6_6] ## What You'll Miss (And Why You Don't Care) **High-speed signals you CAN'T capture:** - **DDR4/DDR5 RAM:** 2-4 GHz[^6_10] - **PCIe:** 2.5-16 GT/s (gigatransfers/second), bandwidth up to 8 GHz[^6_10] - **USB 2.0 High-Speed:** 480 Mbps[^6_11][^6_12] - **Ethernet 100BASE-TX:** 100 Mbps[^6_13] - **CPU internal buses:** GHz range - **HDMI/DisplayPort:** Multi-Gbps **BUT HERE'S THE KEY:** You can't physically access these signals anyway without specialized equipment.[^6_14][^6_15][^6_16] ## Why This Isn't a Problem for Your Repairs ### For Laptop Boot Debugging **What actually controls laptop boot sequence:**[^6_17][^6_18][^6_13] 1. **Embedded Controller (EC):** Communicates via **I2C/SPI at 1-10 MHz**[^6_3][^6_19][^6_13] 2. **Power sequencing:** Enable signals are **DC or slow PWM (<1 MHz)**[^6_20] 3. **Sensor monitoring:** Temperature, voltage sensors use **I2C at 100-400 kHz**[^6_13][^6_11][^6_3] 4. **BIOS chip (SPI flash):** Typically **16-50 MHz** during boot[^6_4][^6_2] **What you can debug with 24MHz analyzer:** - EC communication to mainboard (I2C)[^6_15][^6_13] - Power enable sequences[^6_7][^6_20] - Sensor responses[^6_15][^6_13] - Whether chips are responding to bus queries[^6_13][^6_15] **What you can't debug:** - SPI flash reads during boot (50-100 MHz)—**but** you can detect if the bus is active at all[^6_4][^6_15] - RAM initialization (GHz)—but you don't have physical access anyway[^6_16] ### For Pinephone Display **Display interface signals:** - **MIPI DSI (Display Serial Interface):** Can run 80-500 Mbps per lane[^6_21] - **Too fast for your analyzer**[^6_6] **But the practical diagnostic:** - Display enable signals: **DC level (static)**—multimeter is fine[^6_22][^6_23] - I2C communication to display controller: **100-400 kHz**—logic analyzer works[^6_1][^6_15] - Power rails: **DC**—multimeter is fine[^6_20] **Reality:** Physical cable reseating solves 90% of Pinephone display issues without any analyzer.[^6_21][^6_22] ### For TTL Prototype **Classic TTL/CMOS speeds:** - 74HC logic: Typically 1-25 MHz operation[^6_6] - Arduino/AVR: I2C at 100 kHz, SPI at 1-8 MHz[^6_5][^6_2] - Most homebrew digital projects: <10 MHz[^6_24][^6_9][^6_15] **Your 24MHz analyzer is perfect for this**.[^6_9][^6_25][^6_15] ## The Sampling Math Explained When people say "24 MHz sample rate captures 2-6 MHz signals," here's why:[^6_6] **Digital signal requirements:** - **Minimum (Nyquist):** 2x signal frequency[^6_6] - **Practical for square waves:** 4x signal frequency[^6_6] - **Reliable protocol decoding:** 10x signal frequency[^6_6] **Example: 10 MHz signal** - Nyquist says 20 MHz sampling is enough - **Reality:** At 24 MHz sampling, you get 2.4 samples per cycle[^6_6] - This might catch edge transitions or might miss them entirely[^6_6] - Protocol decoders fail because they can't reliably detect START bits, ACK bits, etc.[^6_9][^6_6] **Example from real testing:** One user tested a cheap 24 MHz analyzer against a Saleae Pro (500 MHz) on a 10 MHz PWM signal:[^6_6] - Cheap analyzer: Couldn't accurately measure duty cycle - Saleae Pro: Perfect capture showing true 50% duty cycle[^6_6] ## What You Actually Need for Laptop Diagnostics **Signals you'll realistically probe:**[^6_26][^6_15][^6_13] 1. **Power rails:** Multimeter voltage measurement[^6_20] 2. **I2C buses (EC, sensors, etc.):** 100-400 kHz—logic analyzer perfect[^6_15][^6_13] 3. **SPI buses (BIOS chip):** 10-50 MHz—24 MHz analyzer will show activity but may not decode perfectly[^6_27][^6_4] 4. **UART debug ports:** 115200 baud (0.115 MHz)—trivially easy[^6_1][^6_5] 5. **GPIO control signals:** Usually <1 MHz—perfect[^6_15] **The \$8 logic analyzer handles items 2, 4, and 5 perfectly**. For item 3 (SPI), you'll see that something is happening, even if individual bits aren't perfectly captured.[^6_28][^6_27][^6_15] ## Real-World Example: Raspberry Pi I2C >From a Hackaday article testing a \$10 24 MHz analyzer on Raspberry Pi I2C bus:[^6_15] - **Signal speed:** 100-400 kHz (typical I2C)[^6_1][^6_15] - **Capture quality:** Perfect[^6_15] - **Protocol decode:** Automatic in PulseView software[^6_28][^6_15] - **Result:** Could see every transaction between CPU and peripherals[^6_15] **Quote:** "This might be one of the cheapest tools you will get... Whether it's debugging weird problems, optimizing your code, probing around a gadget you're reverse-engineering... you are likely missing out a lot if you don't have a logic analyzer"[^6_15] ## When You Actually Need More Speed **If you were debugging:**[^6_14][^6_26][^6_16] - **High-speed USB (480 Mbps):** Need dedicated USB protocol analyzer (\$200+)[^6_12][^6_11] - **Ethernet (100 Mbps+):** Need oscilloscope with protocol decode (\$500+)[^6_13] - **DDR memory:** Need specialized DIMM interposer and GHz analyzer (\$10,000+)[^6_29] - **PCIe:** Need protocol analyzer (\$5,000-50,000)[^6_29][^6_10] **For hobbyist/repair work:** None of these are accessible or necessary.[^6_26][^6_16][^6_15] ## Bottom Line **What you're missing at 24 MHz:** High-speed serial protocols (USB, Ethernet, PCIe, DDR) and fast SPI flash reads.[^6_11][^6_4][^6_10][^6_6] **Why it doesn't matter:** 1. You can't physically access these signals without desoldering chips and using specialized probes[^6_16][^6_14] 2. The actual control logic (I2C, enable signals, sensor buses) runs at speeds your analyzer handles perfectly[^6_1][^6_13][^6_15] 3. For \$8-20, you get 90% of the diagnostic capability of professional tools that cost \$500-5000[^6_26][^6_28][^6_15] **The real limitation isn't speed—it's buffer depth**. The cheap analyzers can only capture milliseconds of data before USB bandwidth becomes the bottleneck. But for boot debugging and protocol troubleshooting, milliseconds is plenty.[^6_9][^6_15][^6_6] **Your best move:** Get the \$8-20 logic analyzer. It will solve your TTL prototype issues completely and help with laptop EC/sensor debugging. For the Pinephone, stick with multimeter + physical inspection.[^6_23][^6_22][^6_28][^6_9][^6_15] <span style="display:none">[^6_30][^6_31][^6_32][^6_33][^6_34][^6_35][^6_36][^6_37][^6_38][^6_39][^6_40][^6_41][^6_42][^6_43][^6_44][^6_45][^6_46]</span> <div align="center">⁂</div> [^6_1]: https://www.wevolver.com/article/i2c-vs-uart [^6_2]: https://www.totalphase.com/blog/2021/12/i2c-vs-spi-vs-uart-introduction-and-comparison-similarities-differences/ [^6_3]: https://www.ti.com/lit/pdf/sbaa565 [^6_4]: https://resources.pcb.cadence.com/blog/2022-comparing-uart-vs-spi-speed [^6_5]: https://forum.arduino.cc/t/why-is-i2c-generally-faster-than-uart/635501 [^6_6]: https://www.reddit.com/r/embedded/comments/10yyddl/cheap_logic_analyzer_precision/ [^6_7]: https://www.reddit.com/r/embedded/comments/nztmn3/any_embedded_software_debugging_tips_and_tricks/ [^6_8]: https://adaptivesupport.amd.com/s/question/0D52E00006iHr6BSAS/choosing-a-logic-analyzer-sample-frequency?language=en_US [^6_9]: https://www.youtube.com/watch?v=2sAJoszsuo8 [^6_10]: https://blog.teledynelecroy.com/2021/09/correlating-low-to-high-speed-events-in.html [^6_11]: https://assets.testequity.com/te1/Documents/pdf/debugging-serial-buses.pdf [^6_12]: https://www.embedded.com/usb-debug-tips/ [^6_13]: https://www.tek.com/en/documents/application-note/debugging-serial-buses-embedded-system-designs-0 [^6_14]: https://www.eevblog.com/forum/testgear/recommendations-on-logic-analyser-for-embedded-debugging/ [^6_15]: https://hackaday.com/2023/08/31/logic-analyzers-tapping-into-raspberry-pi-secrets/ [^6_16]: https://www.reddit.com/r/embedded/comments/n8hcoy/what_is_the_best_cheap_oscilloscope_for_embedded/ [^6_17]: https://www.reddit.com/r/buildapc/comments/mabxmz/troubleshooting_a_debug_boot_led_and_no_signal_on/ [^6_18]: https://www.ibm.com/support/pages/uefi-debug-messages-printed-setup-lenovo-nextscale-nx360-m5-nextscale-nx360-m5-dwc [^6_19]: https://fiveable.me/embedded-systems-design/unit-8/spi-i2c-protocols/study-guide/zgceBCH0J66PwmNO [^6_20]: https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-test-for-continuity [^6_21]: https://forum.pine64.org/showthread.php?tid=19318 [^6_22]: https://www.ifixit.com/Wiki/PinePhone64_Troubleshooting [^6_23]: https://www.linkedin.com/pulse/how-determine-problem-damaged-screen-faulty-flex-cable-jojo-huang-mmfoc [^6_24]: https://www.vogons.org/viewtopic.php?t=74862 [^6_25]: https://www.reddit.com/r/beneater/comments/kl058o/bens_8bit_troubleshooting_tools_logic_analyzer/ [^6_26]: https://www.baldengineer.com/logic-analyzer-tutorial-introduction.html [^6_27]: https://www.uctronics.com/download/Amazon/U6041.pdf [^6_28]: https://learn.sparkfun.com/tutorials/using-the-usb-logic-analyzer-with-sigrok-pulseview/all [^6_29]: http://www.ashling.com/wp-content/uploads/Real-time_trace_a_better_way_to_debug_embedded_applications.pdf [^6_30]: https://wolles-elektronikkiste.de/en/logic-analyzer [^6_31]: https://www.parlezvoustech.com/en/comparaison-protocoles-communication-i2c-spi-uart/ [^6_32]: https://sigrok.org/wiki/Getting_started_with_a_logic_analyzer [^6_33]: https://www.reddit.com/r/embedded/comments/1816dor/uart_vs_spi_vs_i2c/ [^6_34]: https://resources.altium.com/p/i2c-vs-spi-vs-uart-how-layout-these-common-buses [^6_35]: https://wiki.osdev.org/Debugging_UEFI_applications_with_GDB [^6_36]: https://www.andrea-allievi.com/blog/debugging-the-undebuggable-part-1/ [^6_37]: https://www.omi.me/blogs/hardware-guides/how-to-implement-i2c-and-spi-communication-in-embedded-systems [^6_38]: https://www.youtube.com/watch?v=Dm0zLJJYLo0 [^6_39]: https://wiki.congatec.com/wiki/UEFI_Shell_Debugging_(AN51) [^6_40]: https://www.totalphase.com/blog/2021/07/i2c-vs-spi-protocol-analyzers-differences-and-similarities/ [^6_41]: https://forum.pjrc.com/index.php?threads%2Fabout-buying-a-not-too-expensive-logic-analyzer.56496%2F [^6_42]: https://uefi.org/specs/UEFI/2.9_A/07_Services_Boot_Services.html [^6_43]: https://resources.altium.com/p/spi-versus-i2c-how-choose-best-protocol-your-memory-chips [^6_44]: https://interrupt.memfault.com/blog/four-favorite-firmware-debug-tools [^6_45]: https://support.hpe.com/hpesc/public/docDisplay?docId=a00112581en_usen_us\&page=GUID-A7605881-42C0-4583-A05D-986A9D669405.html\&docLocale=en_US [^6_46]: https://www.nxp.com/products/interfaces/ic-spi-i3c-interface-devices/bridges/ic-bus-to-spi-bridge:SC18IS606 --- Now I’m still new to this, but usually if I wanted to troubleshoot a high-speed connection like the display data in the pinephone, I might hope to see noise rather than a ground floor. Can a logic analyzer still help me in situations like that? # Can a Logic Analyzer Detect High-Speed Signal Activity? **Yes, with an important caveat:** A logic analyzer can detect that **something is happening** on a high-speed line, even if it can't accurately decode the data. This is exactly the "noise vs. ground floor" distinction you're thinking about. ## What a Logic Analyzer Actually Sees **Logic analyzers work by threshold detection**:[^7_1][^7_2][^7_3] - They sample an input and compare it to a voltage threshold (typically 1.65V for 3.3V logic)[^7_4][^7_1] - If voltage > threshold: Record "1"[^7_5][^7_1] - If voltage < threshold: Record "0"[^7_1][^7_5] - They **don't** capture the analog waveform shape[^7_2][^7_3][^7_1] **What this means for fast signals:** When you connect a 24 MHz logic analyzer to a 480 Mbps signal (like USB 2.0 high-speed or fast MIPI DSI): - **You'll see rapid toggling between 0 and 1**[^7_6][^7_7] - The pattern will look like random noise because you're undersampling[^7_7][^7_6] - But you **can definitively tell the signal is active** vs. stuck at ground or stuck high[^7_8][^7_9] ## Practical Example: Your Pinephone Display **MIPI DSI display interface** typically runs 80-500 Mbps per lane. Here's what your \$8 logic analyzer (24 MHz sample rate) would show:[^7_10] ### Scenario 1: Display Cable Disconnected - Logic analyzer shows: **Constant "0" (or possibly "1" depending on pull-up/pull-down resistors)**[^7_11][^7_1] - Pattern: Flat line, no transitions[^7_8] - Conclusion: No signal activity—cable problem or mainboard not sending data[^7_12][^7_13] ### Scenario 2: Display Cable Connected, Data Flowing - Logic analyzer shows: **Rapid random-looking transitions**[^7_6][^7_7] - Pattern: Chaotic 0101010110100... that changes every capture[^7_7] - Conclusion: Signal is active—mainboard is sending data[^7_10][^7_8] - **You can't decode what data**, but you know it's there[^7_9][^7_8] ### Scenario 3: Display Cable Connected, No Boot Activity - Logic analyzer shows: **Mostly flat with occasional transitions**[^7_14] - Pattern: Long periods of static state with infrequent changes[^7_1] - Conclusion: Control signals present but no data stream—software/initialization problem[^7_10] ## Why This Works Despite Undersampling **Nyquist theorem says you need 2x signal frequency minimum**, so for 100 MHz signal you need 200 MHz sampling. But for **presence/absence detection** you need far less.[^7_9][^7_8][^7_6][^7_7] **Aliasing actually helps here:**[^7_6][^7_7] - When you undersample a high-frequency signal, it appears as a lower-frequency alias[^7_6] - A 100 MHz square wave sampled at 24 MHz looks like a ~24 MHz pattern (the beat frequency)[^7_6] - This **still shows activity**, just not the true signal[^7_7][^7_6] **Quote from forum:** "If the only thing you care about is 'is there a signal or not,' you can even detect way higher frequencies than the sample rate suggests, because any transition will cause some captured samples to differ"[^7_7] ## Real-World Diagnostic Value **What you can determine with undersampled capture:** 1. **Signal present vs. absent**[^7_8][^7_9] - Ground/power issue vs. disconnected cable vs. active signal[^7_13][^7_11] 2. **Relative timing**[^7_14][^7_1] - Does the display signal start at boot?[^7_10] - Does it appear after other initialization signals?[^7_15][^7_1] - Does it stop when backlight fails?[^7_12] 3. **Correlation with other events**[^7_16][^7_1] - If you capture 8 channels simultaneously, you can see:[^7_17] - Power enable signals (DC level)[^7_11] - I2C initialization to display controller (100-400 kHz—perfectly captured)[^7_18][^7_19] - Display data lanes (high-speed—shows as noise)[^7_7] - Backlight PWM (1-100 kHz—perfectly captured)[^7_7] - Now you know the sequence: "I2C worked, then data started, but backlight never came on"[^7_12][^7_10] 4. **Intermittent faults**[^7_5][^7_1] - Capture shows signal dropouts[^7_1] - Even if you can't read the data, seeing the signal disappear proves cable/connection issue[^7_20][^7_13] ## When You Actually Need an Oscilloscope **For your specific "noise vs. ground" question, an oscilloscope is more definitive**:[^7_3][^7_2][^7_9] **Oscilloscope advantages:** - Shows **voltage levels** continuously[^7_2][^7_3] - Can see weak/marginal signals (voltage between logic thresholds)[^7_3][^7_9] - Detects **signal integrity issues**: ringing, overshoot, crosstalk[^7_3][^7_9] - Sees **analog characteristics** that affect whether signal is decoded properly[^7_2][^7_3] **Example scenario where oscilloscope wins:** MIPI DSI cable is damaged: - **Logic analyzer might show:** Activity detected, looks like data[^7_8][^7_7] - **Oscilloscope shows:** Signal only reaches 1.2V instead of 3.3V—too weak to be decoded by receiver[^7_9][^7_3] - **Reality:** Data is being sent but display can't interpret it due to signal degradation[^7_13][^7_3] **But for \$30 budget:** This level of diagnosis is probably overkill. The logic analyzer's "is there activity?" answer gets you 90% there.[^7_19][^7_21] ## Specific Recommendations for Your Pinephone Given your constraints and goals: **Best diagnostic approach (all free, no tools):** 1. **Visual inspection** of display connector[^7_13][^7_12][^7_10] 2. **Reseat the cable**[^7_12][^7_10] 3. **Press along screen edges while powered** to see if display flickers (indicates loose connection)[^7_20][^7_13] 4. **Check backlight** separately—shine flashlight at screen to see if image is there but backlight is off[^7_12] **If you buy the \$8-20 logic analyzer:** Connect to display flex cable pins and: 1. **Monitor power rails** (3.3V, backlight voltage)—will show as solid "1" if present[^7_4][^7_11] 2. **Monitor I2C control lines** (SCL/SDA)—will perfectly capture initialization commands[^7_18][^7_19] 3. **Monitor data lanes**—will show noise/activity if data is flowing, flatline if not[^7_8][^7_7] **Result:** You'll know if the problem is: - Power (no voltage on power rails)[^7_11] - I2C communication (no/wrong initialization)[^7_19][^7_18] - Data transmission (no activity on data lanes)[^7_10][^7_8] - Physical layer (everything looks right electrically but display doesn't work = cable or panel)[^7_13] ## The Bottom Line **Yes, a cheap logic analyzer helps with high-speed signals for presence detection**:[^7_19][^7_8][^7_7] - You can't decode the data[^7_9][^7_8] - You can't see signal quality issues[^7_3][^7_9] - But you **can** tell "active vs. inactive"[^7_9][^7_8] - And you **can** see timing relationships with other signals[^7_16][^7_1] **For your \$30 budget and multiple broken devices:** - The \$8-20 logic analyzer is worth it[^7_17][^7_19] - It handles all the slow stuff perfectly (I2C, UART, power sequencing)[^7_18][^7_19] - It detects presence/absence of fast signals[^7_8][^7_7] - Combined with your multimeter, you have solid diagnostic coverage[^7_21][^7_22] **You're not missing much** by not having an oscilloscope for this type of repair work. The oscilloscope would show prettier waveforms and catch subtle analog issues, but for "does the Pinephone mainboard send display data or not?", the logic analyzer suffices.[^7_21][^7_19][^7_9][^7_8] <span style="display:none">[^7_23][^7_24][^7_25][^7_26][^7_27][^7_28][^7_29][^7_30][^7_31][^7_32][^7_33]</span> <div align="center">⁂</div> [^7_1]: https://www.tek.com/en/documents/primer/logic-analyzer-fundamentals [^7_2]: https://www.keysight.com/used/us/en/knowledge/guides/logic-analyzer-vs-oscilloscope [^7_3]: https://www.testandmeasurementtips.com/logic-analyzer-basics-the-difference-between-a-scope-and-a-logic-analyzer/ [^7_4]: https://www.uctronics.com/download/Amazon/U6041.pdf [^7_5]: https://www.nutsvolts.com/magazine/article/a_logic_analyzer_tutorial_part_1 [^7_6]: https://www.eevblog.com/forum/beginners/bandwidth-of-logic-analyzer/ [^7_7]: https://www.reddit.com/r/embedded/comments/10yyddl/cheap_logic_analyzer_precision/ [^7_8]: https://digilent.com/blog/what-is-a-logic-analyzer/ [^7_9]: https://forum.etechnophiles.com/equipments/logic-analyzer-vs-oscilloscope/ [^7_10]: https://forum.pine64.org/showthread.php?tid=19318 [^7_11]: https://www.fluke.com/en-us/learn/blog/digital-multimeters/how-to-test-for-continuity [^7_12]: https://www.ifixit.com/Wiki/PinePhone64_Troubleshooting [^7_13]: https://www.linkedin.com/pulse/how-determine-problem-damaged-screen-faulty-flex-cable-jojo-huang-mmfoc [^7_14]: https://www.reddit.com/r/embedded/comments/nztmn3/any_embedded_software_debugging_tips_and_tricks/ [^7_15]: https://www.tek.com/en/documents/application-note/debugging-serial-buses-embedded-system-designs-0 [^7_16]: https://www.totalphase.com/blog/2025/02/oscilloscope-vs-logic-analyzer-vs-protocol-analyzer-understanding-roles-debugging/ [^7_17]: https://learn.sparkfun.com/tutorials/using-the-usb-logic-analyzer-with-sigrok-pulseview/all [^7_18]: https://www.wevolver.com/article/i2c-vs-uart [^7_19]: https://hackaday.com/2023/08/31/logic-analyzers-tapping-into-raspberry-pi-secrets/ [^7_20]: https://xdaforums.com/t/q-black-screen-loose-cable.2366178/ [^7_21]: https://www.baldengineer.com/logic-analyzer-tutorial-introduction.html [^7_22]: https://www.youtube.com/watch?v=SSp1wn0Abck [^7_23]: https://www.suindigital.com/logic-analyzer/591.html [^7_24]: https://digilent.com/reference/test-and-measurement/guides/waveforms-logic-analyzer [^7_25]: https://www.teledynelecroy.com/logicanalyzers/ [^7_26]: https://forum.arduino.cc/t/what-does-a-logic-analyzer-do/56455 [^7_27]: https://www.saleae.com [^7_28]: https://www.reddit.com/r/AskElectronics/comments/1rz1cs/would_i_need_an_oscilloscope_or_logic_analyzer/ [^7_29]: https://discuss.saleae.com/t/measure-can-bus/2123 [^7_30]: https://www.keysight.com/us/en/products/logic-analyzers.html [^7_31]: https://www.electronicdesign.com/technologies/test-measurement/article/21800885/whats-the-difference-between-a-mixed-signal-oscilloscope-and-a-logic-analyzer [^7_32]: https://www.reddit.com/r/CarHacking/comments/7hs2d9/logic_analyzer_for_can_bus/ [^7_33]: https://engineering.case.edu/sites/default/files/Tektronix Logic Analyzer - Fundamentals.pdf
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