RE: PDP 11 gear finally moved
On Mon, 20 Jul 2015, Rich Alderson wrote: the aluminum electrolytics that indicate that, *no matter what*, they lose capacitance over time, until c. 14 years from manufacturer date they are at 10% of rating. Please excuse me, but this is utter nonsense. Most electrolytics in our machines are 30 years and older, and they just work. Those caps that I checked (mostly large filter/smoothing caps), e.g. those from the LGP-30 (nearly 60 years old) or Mincal 523 (44 years old), are just fine. Smaller ones don't even have to be bothered with. OTOH foil caps from the 50s/60s (e.g. ERO/EROFOL/EROID/Wima) tend to lose a bit of their isolation and become resistive (several MOhm). This can be a problem with AC coupling in tube circuits. Also problematic are more modern foil caps in line filters (e.g. X/Y caps), or even oil filled MP caps in power supply (magnetic constanters, filters) or motor applications (phase shifters). But admittedly I don't know what crappy electrolytics you have encountered in your "industry grade" machines. Or are we talking of modern machines (<30 years) ? [1] NB: I am not now, nor have I ever claimed to be, a hardware engineer of any stripe, and more particularly not an electronics specialist. I am, nonetheless, capable of reading and understanding research papers with statistics that back up the claims being made even if I could not devise the experiment to test them. I rely on my colleagues who are experts to assure me that the writers are not smoking crack. Statistics... don't believe any statistic that you haven't faked yourself. Honestly, IMO this doesn't really qualify you as expert in capacitors. I think those statistics are based on running the caps 24/7 at their nominal ratings, but surley they don't apply to moderate museum usage. Christian
RE: PDP 11 gear finally moved
On Tue, 21 Jul 2015, tony duell wrote: But yes, selenium rectifiers rarely work now (although there are exceptions) and when they fail they can take out the mains transformer. And they smell horrible (think of school dinner cabbage!) Huh? All devices with selenium rectifiers that I/we own are OK. And a selenium rectifier only fails if overloaded. See for example the power supply of the LGP-30: http://computermuseum.informatik.uni-stuttgart.de/dev_en/lgp30/lgp30.html Note: the height is about 60cm, power rating IIRC somewhere between 500 and 1000W! And all my radio/TV sets with selenium rectifiers are OK, too. I had to replace one in my TV as it had a too high resistance, but only because I didn't know at that time that I could re-fasten the nuts of the rectifier (selenium rectifier plates can suffer from contact resistances). Christian
RE: PDP 11 gear finally moved
> > > But yes, selenium rectifiers rarely work now (although there are exceptions) > > and when they fail they can take out the mains transformer. And they smell > > horrible (think of school dinner cabbage!) > > Huh? All devices with selenium rectifiers that I/we own are OK. And a > selenium rectifier only fails if overloaded. See for example the power > supply of the LGP-30: I've had many more selenium rectifiers fail than electrolytics. But actually yes, I do still have some original selenium rectifiers in operation. Come to think of it, every UK Telephone 706, 746, 722, 776, etc (The common 1970's telephones) had a selenium rectifier stack ( 8 diodes) as part of the voltage regulator circuit. I have never heard of one of those failing. > And all my radio/TV sets with selenium rectifiers are OK, too. I had to > replace one in my TV as it had a too high resistance, but only because I > didn't know at that time that I could re-fasten the nuts of the rectifier > (selenium rectifier plates can suffer from contact resistances). The ones I mainly have are those flat 'contact cooled' ones that you bolt onto the chassis. You can take those apart and bend contacts, etc, but most of the time I replace them with a suitable silicon device. -tony
Beaglebone Black rev B sale
http://www.microcenter.com/product/430528/BeagleBone_Black# There aren't any stores in the SF Bay area, so this won't do me any good, and it isn't clear how many are available.
Front Panel update
Hi Guys As usual I try to keep you updated on front panel progress. (Always supposing I know where I am!!) I now have _prototype_ white seperation artwork for four front PDP8 panels 1. pdp8/e Type A 2. pdp8/e Type B 3. pdp8/f 4. pdp8/m I am doing all four together as they share the same basic plexiglass panel. There's a lot to do to to get to the point they can be silkscreened. I have put all four as they now stand in a file (.svg) and if you email me direct I'll send it to you. Rod
Re: MEM11 Update
> From: Guy Sotomayor > I took some time off from working on the MEM11 ... I had some time over > the past few days, so I spent it working on the simulator. Excellent news! > Right now all of the J1 instructions seem to simulate properly. I had to go hunt up your original message: http://www.classiccmp.org/pipermail/cctalk/2015-January/002879.html to refresh my memory as to exactly what a 'J1' was! It was interesting to re-read your original message; I and a couple of other people are looking into doing a QBUS card to provide access to modern non-volatile storage (SD cards, USB thumb drives), and in discussing the internal design, we'd planned on an FPGA, and a separate micro-controller. Your concept to have the 'micro-controller' _in_ the FPGA is interesting! The only problem, from our point of view, is the 'limited' number of FPGA pins (the QBUS interface alone is ~50 pins) - at least, without going to a BGA part, which we view as undesirable. > Everything related to the basic simulator also seems to be functional. I'm curious as to your reasoning in doing a custom simulator (OK, it's all fun :-). I do understand having _a_ simulator (writing all the software involved on the card will be much easier if you don't have to deal with a flaky/new hardware), but since the J1 is in the FPGA, couldn't you just use the FPGA simulator? Or is it too slow to emulate a good-sized J1 program? Noel PS: When we get down to detailed design, we'll have to get the specs on your light panel interface; we'd like to be able to drive the same light panel (for exactly the same uses :-), to avoid re-building the wheel.
RE: PDP 11 gear finally moved
> From: a...@p850ug1.demon.co.uk > To: cctalk@classiccmp.org > Subject: RE: PDP 11 gear finally moved > Date: Sun, 19 Jul 2015 14:35:52 + > > > > > Be careful, static daamge does not always show up at the time. You can > damage an IC, have it work for some time afterwards and then fail. > I'm quite aware of that. I've looked under a microscopeat some parts that were mishandled but still working.For how long, one can only guess.Dwight > -tony
Re: PDP 11 gear finally moved
On Mon, 20 Jul 2015 23:14:36 -0600 Eric Smith wrote: > On Mon, Jul 20, 2015 at 4:46 PM, Rich Alderson > wrote: > > industry white papers with tables of decay rates for > > the aluminum electrolytics that indicate that, *no matter what*, they lose > > capacitance over time, until c. 14 years from manufacturer date they are at > > 10% > > of rating. > > That's very interesting. I haven't seen those white papers, but the > "no matter what" must in fact depend on something, since on the PDP-1 > Restoration Project we found that most of the 40 year old aluminum > electrolytic capacitors still met their original specifications, > including capacitance within rated tolerance. Of the few electrolytic > capacitors that had failed, the problem was a catastrophic failure, > not the capacitance being outside the rated tolerance. > > In the PDP-1, we preferred to keep the original components as much as > possible. Had there been a capacitor, the failure which would have > caused extensive damage to other components, we would have given > serious consideration to replacing it. However, that was not the case > for any of the capacitors in the PDP-1. > > Had our analysis indicated any expected benefit to replacing all of > the electrolytic capacitors, we would have done so, and bagged and > tagged the originals similar to what we did with failed components, so > that they could be replaced if it ever was desired to return the > artifact to its pre-restoration condition. > > I'm not recommending against LCM's policy, but I also wouldn't > necessarily encourage anyone to adopt it, nor to adopt the practices > of the CHM PDP-1 Restoration Project, without studying the issue. As Eric, I'm a member of the PDP-1 Restoration Team. The PDP-1 restoration was completed in 2005 - and annually we check the power supplies for voltage, ripple, etc. Not one of the re-formed capacitors have failed in the ten years since the completion of the restoration. I also re-formed all P/S capacitors in my PDP-8/S in September, 2013. Not one has failed since... Same with my EAI TR-20 Analog computer. And so it is for all the systems in my collection... IMHO, these "white papers" indicating that ALL aluminum electrolytic capacitors decay is obvious nonsense - based on real life experience - not someones theory... Lyle -- 73 AF6WS Bickley Consulting West Inc. http://bickleywest.com "Black holes are where God is dividing by zero"
Re: Beaglebone Black rev B sale
On Tue, Jul 21, 2015 at 6:34 AM, Al Kossow wrote: > http://www.microcenter.com/product/430528/BeagleBone_Black# > > There aren't any stores in the SF Bay area, so this won't do me > any good, and it isn't clear how many are available. My local Micro Center is the main store. I just checked - they are out of stock there. From offers like this in the past, the quantity per store is quite low - 4-6 usually, rarely as much as 10 for such a deep discount. They routinely have large stock at the $5-$10-off MSRP price point. -ethan
Re: PDP 11 gear finally moved
- Original Message - From: "Tothwolf" Sent: Monday, July 20, 2015 10:03 PM ... I too am getting tired of repeating the same thing over and over; compiling this sort of information in a single location might be helpful. As it happens I am getting tired of _reading_ the same thing over and over; another of those Windows/Linux, PC/Mac etc. debates that contribute little and never change anyone's opinion. By all means, compile a _balanced_ summary and host it somewhere for reference. I suspect that the real criterion for whether to shotgun-replace caps is who is paying/getting paid for the materials and labour ;-). FWIW I'm certainly not about to spend 100s of dollars, not to mention time spent in sourcing and replacing, to replace the caps in systems that are running perfectly "just in case"... m
Re: MEM11 Update
On 7/21/15 6:25 AM, Noel Chiappa wrote: It was interesting to re-read your original message; I and a couple of other people are looking into doing a QBUS card to provide access to modern non-volatile storage (SD cards, USB thumb drives), and in discussing the internal design, we'd planned on an FPGA, and a separate micro-controller. Your concept to have the 'micro-controller' _in_ the FPGA is interesting! The only problem, from our point of view, is the 'limited' number of FPGA pins (the QBUS interface alone is ~50 pins) - at least, without going to a BGA part, which we view as undesirable. The Xylinx Spartan 3E in a TQFP package has 144 pins and it's *just* enough for the Unibus and talking to the other peripherals. I haven't looked, but I think the Unibus and QBus are comparable in terms of pin count. I *did* have to make some compromises (ie the DUART is connected through SPI...couldn't afford the pins for the modem controls unless I did that). > Everything related to the basic simulator also seems to be functional. I'm curious as to your reasoning in doing a custom simulator (OK, it's all fun :-). I do understand having _a_ simulator (writing all the software involved on the card will be much easier if you don't have to deal with a flaky/new hardware), but since the J1 is in the FPGA, couldn't you just use the FPGA simulator? Or is it too slow to emulate a good-sized J1 program? The J1 doesn't have any exceptions or other debugging aids. I wrote the simulator to be timing accurate from the J1's perspective (so that I could check timings and such) and that I could single step the J1, set breakpoints, examine memory and do instruction tracing. It's also my behavioral model for the Verilog code in the FPGA. So before I commit to a lot of Verilog code, I know how it will behave and how hard it is to write the firmware. The approach that I'm taking is that as much as possible is being written in forth. It's only if it will be too slow or too much code to implement a function, will I put it into Verilog. For example, unless I find some egregious timing problem, most of the Unibus transactions are written in F/W. I'm leaving the Verilog for handling the lowest level details. TTFN - Guy
Re: PDP 11 gear finally moved
On 21/07/2015 06:14, Eric Smith wrote: On Mon, Jul 20, 2015 at 4:46 PM, Rich Alderson wrote: industry white papers with tables of decay rates for the aluminum electrolytics that indicate that, *no matter what*, they lose capacitance over time, until c. 14 years from manufacturer date they are at 10% of rating. That's very interesting. I haven't seen those white papers, but the "no matter what" must in fact depend on something, since on the PDP-1 Restoration Project we found that most of the 40 year old aluminum electrolytic capacitors still met their original specifications, including capacitance within rated tolerance. Yep, I find "no matter what" and "10%" very hard to believe for similar reasons. For one example, the aluminium electrolytics I recently took out of a 4-decade-old PDP-8/L were fine after reforming. In fact based on my tests I'd say they were well within their stated tolerance. My other PDP-8s, of not dissimilar vintage, are running fine. As is my c.2000 Origin 2000, my several other SGIs (some of which have been in regular use since the mid 90s, and two have been running 24/7 with only brief interruptions over that period), assorted PDP-11s, ... -- Pete Pete Turnbull
Re: MEM11 Update
-Oorspronkelijk bericht- From: Guy Sotomayor Sent: Monday, July 20, 2015 11:04 PM To: General@main.local ; Discussion@main.local:On-Topic and Off-Topic Posts Subject: MEM11 Update As I mentioned previously, I took some time off from working on the MEM11 for the past several months. I had some time over the past few days, so I spent it working on the simulator. [...snip ...] Oh, and of course everything (simulator, MEM11 firmware and tools for the build environment) are all written in forth. ;-) TTFN - Guy Hi Guy, great job, thumbs up! Thanks Noel for looking up the previous post. Your planning is very good Guy, you seem to be on track. Following this with much interest as I have a CPU-only PDP-11/20. This design will make it "complete" with a single board. I do have an RK11-D (somewhere). However, I have no experience with forth :-( greetz, - Henk
Re: PDP 11 gear finally moved
On 7/21/2015 9:04 AM, Lyle Bickley wrote: IMHO, these "white papers" indicating that ALL aluminum electrolytic capacitors decay is obvious nonsense - based on real life experience - not someones theory... The whole problem with the caps is the water between foil. As modern caps use more and more tricks to improve the surface area,the water margin gets thinner and thinner.At least with GOOD vacuum tube equipment you could replace caps. Ben.
Two Rescues, Too much stuff to add to the project list...
Folks, With the help of my local rescue buddy (Jeff) we had a pretty busy week rescuing a big chunk of things from basements. (and saw a lots of other interesting things... a 90% assembled Rutan EZ in one basement and a very cool, oscilloscope that would probably have have had a lot of folks drooling...a KS-15512-L5 made for Western Electric by Polarad Electronics ...we DID ask about it, but so far he's holding on to it.. but we did get a couple of tube radios for a local AHCS member) I had to pay for some of the material (and both had a "take it all/most" sort of requirement) so my goal is to at least cover my costs (the Wife lets me keep doing so if I keep it at a $0 or positive number... and so far, I have...amazingly enough). Keep that in mind... this isn't going to be a give away... but I'm not trying to make a living here, just didn't want to see stuff end up in the scrap heap. And if I can keep a couple machines. And to be honest, after looking thru all of this, I'm simply not going to have time to restore all of it... the project list is long enough... Here's the list: 1x HP 85 B (plus 3 modules, I'll have to check them out in further detail) 1x HP 9816 with 9131 dual disk drive 4x Otrona Attache's (and a huge plastic tub of original replacement parts... a first look indicates enough to build at least 1 more machine) Some of these have the 8086 accessory board that allows it to run MS-DOS (along with the CPU it normally runs with it's Z80) 1x Wang Model 370 Calculating System with a Model 372 Data Storage System. 2x SOL 20's (and a couple of Micropolis 720 DSDD blue drives for one... ) 1x Zenith H-19 (this may have been updated to a newer model, I haven't dug into it much) 1x Mitsubishi MP-2010 Laptop And there is a pile of SW... believe I have at least a boot disk for each. I've not tried to power anything up (it was a busy week driving around town picking up stuff) except for one Otrona which did seem to have some life, but didn't boot or show anything on the screen. But I haven't checked inside anything so could be simple (And yes, I only tried powering it on because of the HUGE box of spare parts... so was willing to have something emit the magic smoke the curiosity simply was too much :-) ) There are a few assorted terminals and various spare parts that I got as well. If you're interested in anything ping me... and we can see if we can work out details/trade/etc. Pictures can be sent or posted... again, not enough time to get that done yet. One other thing, I'm hoping to get to VCF MW (or at least be able to have someone who is going carry some things) so if you're going to be there, I we could use that to save shipping. I don't have a problem shipping either. EarltheSquirrel.
Re: MEM11 Update
On 7/21/15 10:23 AM, Henk Gooijen wrote: -Oorspronkelijk bericht- From: Guy Sotomayor Sent: Monday, July 20, 2015 11:04 PM To: General@main.local ; Discussion@main.local:On-Topic and Off-Topic Posts Subject: MEM11 Update As I mentioned previously, I took some time off from working on the MEM11 for the past several months. I had some time over the past few days, so I spent it working on the simulator. [...snip ...] Oh, and of course everything (simulator, MEM11 firmware and tools for the build environment) are all written in forth. ;-) TTFN - Guy Hi Guy, great job, thumbs up! Thanks Noel for looking up the previous post. Your planning is very good Guy, you seem to be on track. Following this with much interest as I have a CPU-only PDP-11/20. This design will make it "complete" with a single board. I do have an RK11-D (somewhere). However, I have no experience with forth :-( Thanks. I'm finding that I'm wishing it were done because I need some of the functionality that it'll provide *now*. ;-) Don't worry all of the forth-ness is hidden. It just happens to be the implementation language and the J1 was designed to execute forth efficiently. TTFN - Guy
Re: Two Rescues, Too much stuff to add to the project list...
On 7/21/15 12:10 PM, Earl Baugh wrote: Folks, 4x Otrona Attache's (and a huge plastic tub of original replacement parts... a first look indicates enough to build at least 1 more machine) Some of these have the 8086 accessory board that allows it to run MS-DOS (along with the CPU it normally runs with it's Z80) Could you dump the roms and take some pics of the boards?
RE: Two Rescues, Too much stuff to add to the project list...
Since you have the HP-85, I'll mention this: http://www.vintagecomputers.freeserve.co.uk/hp85/prm85.htm I have one... it's the ultimate for HP-85 owners. J -Original Message- From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Earl Baugh Sent: Tuesday, July 21, 2015 2:11 PM To: cctalk@classiccmp.org Subject: Two Rescues, Too much stuff to add to the project list... Folks, With the help of my local rescue buddy (Jeff) we had a pretty busy week rescuing a big chunk of things from basements. (and saw a lots of other interesting things... a 90% assembled Rutan EZ in one basement and a very cool, oscilloscope that would probably have have had a lot of folks drooling...a KS-15512-L5 made for Western Electric by Polarad Electronics ...we DID ask about it, but so far he's holding on to it.. but we did get a couple of tube radios for a local AHCS member) I had to pay for some of the material (and both had a "take it all/most" sort of requirement) so my goal is to at least cover my costs (the Wife lets me keep doing so if I keep it at a $0 or positive number... and so far, I have...amazingly enough). Keep that in mind... this isn't going to be a give away... but I'm not trying to make a living here, just didn't want to see stuff end up in the scrap heap. And if I can keep a couple machines. And to be honest, after looking thru all of this, I'm simply not going to have time to restore all of it... the project list is long enough... Here's the list: 1x HP 85 B (plus 3 modules, I'll have to check them out in further detail) 1x HP 9816 with 9131 dual disk drive 4x Otrona Attache's (and a huge plastic tub of original replacement parts... a first look indicates enough to build at least 1 more machine) Some of these have the 8086 accessory board that allows it to run MS-DOS (along with the CPU it normally runs with it's Z80) 1x Wang Model 370 Calculating System with a Model 372 Data Storage System. 2x SOL 20's (and a couple of Micropolis 720 DSDD blue drives for one... ) 1x Zenith H-19 (this may have been updated to a newer model, I haven't dug into it much) 1x Mitsubishi MP-2010 Laptop And there is a pile of SW... believe I have at least a boot disk for each. I've not tried to power anything up (it was a busy week driving around town picking up stuff) except for one Otrona which did seem to have some life, but didn't boot or show anything on the screen. But I haven't checked inside anything so could be simple (And yes, I only tried powering it on because of the HUGE box of spare parts... so was willing to have something emit the magic smoke the curiosity simply was too much :-) ) There are a few assorted terminals and various spare parts that I got as well. If you're interested in anything ping me... and we can see if we can work out details/trade/etc. Pictures can be sent or posted... again, not enough time to get that done yet. One other thing, I'm hoping to get to VCF MW (or at least be able to have someone who is going carry some things) so if you're going to be there, I we could use that to save shipping. I don't have a problem shipping either. EarltheSquirrel.
RE: PDP 11 gear finally moved
Rich Alderson wrote: > >From: Peter Coghlan >Sent: Saturday, July 18, 2015 1:27 AM > >> Rich Alderson wrote: > It is generally a good idea to re-form electrolytic capacitors in power supplies, and to bench check the power supplies (under some kind of load) before actually applying power to the whole unit. > >>> It is always a good idea to replace electrolytic capacitors in power >>> supplies. >>> The rest of the advice is sound. > >> Can you please clarify if this statement represents the policy of the Living >> Computer Museum or is it something more personal? Perhaps some qualification >> or a re-phrasing would be useful as it does not appear to make sense as it >> stands? > >This is the policy of Living Computer Museum. It is based on the cumulative >experience of multiple very senior electrical engineers[1] doing restorations >here, in conjunction with industry white papers with tables of decay rates for >the aluminum electrolytics that indicate that, *no matter what*, they lose >capacitance over time, until c. 14 years from manufacturer date they are at 10% >of rating. > >When, in 2004, we first began restorations of the systems that eventually >became LCM, we followed the sage advice of those who described how to "re-form" >electrolytic capacitors. Months of frustrating results eventually led to the >search for industry literature on the topic; the result of that research was >the formulation of our policy regarding this practice--that it is not worth the >time and effort for minimal results. > >> I think you may have seen or participated in some of the many discussions we >> have had on this topic on this list? In light of these discussions, I find >> it >> hard to see how a categorical statement such as this one could be justified. > >Since the proponents of this practice make categorical statements with no >evidence that they want to listen to reasoned explanations, I long ago gave >over trying to convince them, and simply respond when someone makes a statement >to a newbie which will result in frustration and failure for the unfortunate >recipient of this advice. > > >Rich > > >[1] NB: I am not now, nor have I ever claimed to be, a hardware engineer of >any stripe, and more particularly not an electronics specialist. I am, >nonetheless, capable of reading and understanding research papers with >statistics that back up the claims being made even if I could not devise >the experiment to test them. I rely on my colleagues who are experts to >assure me that the writers are not smoking crack. > > >Rich Alderson >Vintage Computing Sr. Systems Engineer >Living Computer Museum >2245 1st Avenue S >Seattle, WA 98134 > >mailto:ri...@livingcomputermuseum.org > >http://www.LivingComputerMuseum.org/ > Hi Rich, Thank you for providing further clarification but please understand that I was trying to give you an opportunity to get out of the hole you were digging, not trying to encourage you to dig deeper. I was hoping to avoid going back over the issues which have been previously debated at length on the list without reaching any conclusions other than that different people have different strongly held views on the subject but I guess that was too much to hope for :-( Regards, Peter Coghlan.
Re: PDP 11 gear finally moved
On Tue, 21 Jul 2015, Mike Stein wrote: I suspect that the real criterion for whether to shotgun-replace caps is who is paying/getting paid for the materials and labour ;-). I dunno about that. When I've done commercial boards such as industrial process controllers and CPUs for customers with nearly unlimited funds, I charged the customer based on an hourly rate. Since I use a vacuum desoldering tool, changing out 10-15 aluminum electrolytics on a board took me not much more time than 1-2. Most of the time spent on a board that comes out of the field is spent on cleaning, testing (before and after repairs) and prep, and it only takes a few seconds to pull the solder off of a couple of component leads. Replacing aged electrolytics wholesale on these types of boards also meant I didn't need to worry that the same board would be back on my bench again in the next 3-6 months. These days, I'm not taking on any new commercial work though, there was just too much demand due to all those shoddy far-east made capacitors, and it meant I pushed aside all my own projects. I guess from a business standpoint, if I had been trying to make extra money on boards repeat failing in the field and having to come back in for repairs over and over, changing out only 1 or 2 aluminum electrolytics would have made sense. That said, industrial process equipment tends to run 24/7 and is expected to be 100% reliable. If something shuts down, it tends to cost a heck of a lot of money, so I would no doubt have lost many customers. FWIW I'm certainly not about to spend 100s of dollars, not to mention time spent in sourcing and replacing, to replace the caps in systems 100s? Where are you sourcing your components from? The typical board I rebuild has a component cost of about $20 or less. Smaller switchmode PSUs with a bunch of 10-18mm radials might be closer to $35-50. Larger PSUs /might/ cost closer to $100 if they have several large screw terminal capacitors in them. All things considered, that isn't very much money in today's dollars, and considering the full replacement cost of some of these boards (if they are even available), those preventive maintenance costs are an absolute bargain, /especially/ if you are doing the work yourself on your own time. that are running perfectly "just in case"... How do you -know- they are "running perfectly"? Just because a widget itself is functioning, you have no way of knowing if that capacitor is working 100% properly /unless/ you actually remove it from circuit and run a full battery of tests on it. Simply measuring the capacitance with a DMM while a capacitor is in circuit isn't good enough. Given that a typical aluminum electrolytic capacitor costs anywhere from $0.12-$0.15 (4mm or 5mm diameter radials) to about $1.00 (12mm or 16mm diameter radial), it also doesn't make much sense to desolder a 20 year old part, spend at a minimum 5 or more minutes testing it, and then solder it back in. It it much more economical to pull the old part and install a new one and be done with it. (You also don't have to worry if the desoldering and resoldering process might have damaged the original parts end-seals.) That said, I personally pre-test new parts, in bulk, before I put them into my stock, so I know ahead of time that I'm installing known-good parts. On many occasions I've cut open old aluminum electrolytics, and the guts very much do deteriorate with age. In addition to corrosion of the foil (black spots and pitting) and foil to terminal junctions (corrosion), one thing I particularly noticed was the more operating hours an aluminum electrolytic capacitor had on it, the more its electrolyte and paper insulator tended to smell bad compared to an otherwise identical (same brand and series) part that had very low hours. These are all clear signs of deterioration. To those who advocate keeping old aluminum electrolytics in service, I have to also ask, would you also try to recondition 20 year old NiCd or SLA batteries and keep those in service too? The bottom line really is, if you want something to be as reliable as you can possibly make it, you replace old aluminum electrolytic capacitors which are outside of their expected service life. If you don't care if something fails over and over, or you actually like to have the same widget on your service bench year after year, or month after month, you just replace 1 or 2.
Re: PDP 11 gear finally moved
On Tue, 21 Jul 2015, ben wrote: On 7/21/2015 9:04 AM, Lyle Bickley wrote: IMHO, these "white papers" indicating that ALL aluminum electrolytic capacitors decay is obvious nonsense - based on real life experience - not someones theory... The whole problem with the caps is the water between foil. As modern caps use more and more tricks to improve the surface area,the water margin gets thinner and thinner.At least with GOOD vacuum tube equipment you could replace caps. One of those tricks they use in modern aluminum electrolytics is to emboss or etch the foil. This gives it more surface area, so they can use a smaller amount of foil and obtain the same capacitance. The foil and insulator in many modern parts is also much thinner.
Re: PDP 11 gear finally moved
On Mon, 20 Jul 2015, Mark J. Blair wrote: On Jul 20, 2015, at 18:02 , Tothwolf wrote: I replace wax paper types with polyester (mylar), polystyrene or ceramic discs, depending on how they are used in the circuit (note however that for wound foil types, modern replacement parts do not mark the outside foil, which needs to be at ground potential in many tube circuits, otherwise the circuit can pick up noise and hum). Funny that you mentioned that! I just watched a YouTube video today about how to experimentally determine which lead is connected to the outer foil for applications where that's important. Modern film caps may have a stripe on one end, but it doesn't appear to reliably indicate which lead goes to the outer foil. I've often wondered why they even bother to put that polarity stripe on modern film parts when it doesn't actually indicate the outside foil terminal. Maybe this is something that has become lost knowledge to manufacturers over the years to the point where even Vishay/Sprague doesn't know what that black indicator stripe was actually used for?
Re: PDP 11 gear finally moved
On 07/21/2015 06:46 PM, Tothwolf wrote: I dunno about that. When I've done commercial boards such as industrial process controllers and CPUs for customers with nearly unlimited funds, I charged the customer based on an hourly rate. Since I use a vacuum desoldering tool, changing out 10-15 aluminum electrolytics on a board took me not much more time than 1-2. Most of the time spent on a board that comes out of the field is spent on cleaning, testing (before and after repairs) and prep, and it only takes a few seconds to pull the solder off of a couple of component leads. Replacing aged electrolytics wholesale on these types of boards also meant I didn't need to worry that the same board would be back on my bench again in the next 3-6 months. These days, I'm not taking on any new commercial work though, there was just too much demand due to all those shoddy far-east made capacitors, and it meant I pushed aside all my own projects. Commercial/industrial boards are a whole different matter and I agree with you there. The quality of the service performed is of more importance, often that the cost. Consider a floppy controller board for a name-brand PLC. You can get one for about $5000--not the PLC, but the floppy board. The customer expects the PLC to last the life of the tool it's controlling--30 years is not atypical. I've often thought that if some of the scrappers out there could recognize some of the stuff they ground up for precious metals, they'd think twice. I might think twice about doing a board that was fragile with age, but otherwise, change 'em all. Like replacing both headlight bulbs if one goes out--it's just a matter of time before the other one goes. --Chuck
Re: PDP 11 gear finally moved
On 07/21/2015 06:56 PM, Tothwolf wrote: I've often wondered why they even bother to put that polarity stripe on modern film parts when it doesn't actually indicate the outside foil terminal. Maybe this is something that has become lost knowledge to manufacturers over the years to the point where even Vishay/Sprague doesn't know what that black indicator stripe was actually used for? And not so modern parts. I've still got a few pounds of paper-oil capacitors (lots of Rifas) from the 1980s. Picked them up as mixed NOS priced about 25 cents per pound. About half are market with polarity marks. I never understood why. I used one recently to replace an ignition capacitor in a 40 year old chainsaw (a Stihl 056). Works a treat. --Chuck
RE: PDP 11 gear finally moved
On Tue, 21 Jul 2015, tony duell wrote: On Mon, 20 Jul 2015, Tothwolf wrote: Yes, the grid cap would /usually/ be a non-polarized wax paper type, which tend to be very unreliable. I've yet to find a wax paper type which will pass a leak test and those are also on my replace on sight list. Of course you wouldn't want to replace mica, ceramic, or plastic film parts without good reason, but if a set is going to be more than just a shelf queen, aluminum electrolytics and wax paper capacitors are a It depends a lot on the circuit. If replacing the capacitor is going to involve major realignment and the original is probably OK and leakage is not going to do further damage (likely in the case of a tuning component) then I will leave it and only replace if it fails. IMO an alignment is simply part of the restoration process. When I service a set, I do so expecting that it is going to be used and thus needs to have an accurate dial vs just sitting on a shelf. Simply installing replacement aluminum electrolytics and wax-paper capacitors is not likely to affect alignment. It is extremely common however to find sets where someone else has previously mucked up the original alignment in an attempt to work around electrically leaky wax-paper capacitors which have caused the band the drift. must-replace item. Carbon film resistors in this sort of equipment should also be tested, however I only replace those which are either bad or out of tolerance (some brands held up better than others). This is inconistent. A capacitor which is failing (starting to leak, say) may get worse. A resistor which is drifting may get worse. Either can do more damage when it fails. Why replace the cap and not the resistor? Why is that inconsistent? If I test a carbon comp resistor and it measures within spec, there isn't much reason to replace it. Unlike an aluminum electrolytic capacitor, a carbon comp resistor is very stable chemically. Carbon comp resistors tend to drift due to absorption of moisture, and while it is possible to dry one out in a toaster oven at a controlled temperature, the resistor will again drift out again over time, so if one is out of spec, replacement is the best option. I probably would replace certain safety-related capacitors in live chassis sets, like ones that isolate external sockets, using class Y replacements. But that;s about it. That's a good idea, however something to keep in mind is that class Y safety rated capacitors are not designed not to short (and not put say a I thought that was the difference between class X (will fail in a safe way, but may short) and class Y (will not short). The latter are to be used where 'failure of the capacitor may expose a person to electric shock' according to the data sheets I've read. In general class X go across the mains, class Y from mains to ground. Except that the chassis in modern equipment is /expected/ to be connected to ground, unlike a floating or hot chassis in a vintage radio. Both class X and class Y can fail short. A class Y tends to have a thicker dielectric and/or a lower voltage rating, which means it is less likely to fail short, not that is cannot fail short. I consider replacing aluminum electrolytics to be preventive maintenance. One wouldn't drive a 20-50 year old car with original hoses, belts, and tires, and IMO it is just common sense to replace electronic components such as aluminum electrolytic capacitors which have extremely well documented life expectancies and failure rates. I do wonder if this data is based on the cheaper components used in consumer electronics (paticularly things like AA5s) and that the capacitors used in computers were of a much higher quality and longer life. Possibly. Radio repair shops of the AA5 era also had a vested interest in turning a set around as quickly (and as cheaply) as possible, and a set back in again in the same year for another repair was also good for their business. Back then, consumers expected their radios to need "routine" service, so people were less likely to even question it. I've come to this conclusion based on the types and quality of radio shop repairs I've seen in these old sets. I have a radio in my to-do queue right now (an AA5) which was owned by my grandparents, where a shop needlessly hacked the leads off a Centralab hybrid module and replaced about half of its functionality with some really cheap wax-paper capacitors and a handful of resistors (after searching for a number of years, I actually managed to find a NOS module for it, so that part of the circuit will be restored to its original condition when I eventually get to that project). As far as shotgun-repairs go, one of my own pet peeves are those out there selling "cap kits" (usually really low quality [sometimes counterfeit] Oh don't get me started Cap kits or counterfeits? ;) Best way to avoid counterfeits...do not buy modern name b
Re: PDP 11 gear finally moved
- Original Message - From: "Tothwolf" To: "General Discussion: On-Topic and Off-Topic Posts" Sent: Tuesday, July 21, 2015 9:46 PM Subject: Re: PDP 11 gear finally moved On Tue, 21 Jul 2015, Mike Stein wrote: ... FWIW I'm certainly not about to spend 100s of dollars, not to mention time spent in sourcing and replacing, to replace the caps in systems 100s? Where are you sourcing your components from? The typical board I rebuild has a component cost of about $20 or less. Smaller switchmode PSUs with a bunch of 10-18mm radials might be closer to $35-50. Larger PSUs /might/ cost closer to $100 if they have several large screw terminal capacitors in them. All things considered, that isn't very much money in today's dollars, and considering the full replacement cost of some of these boards (if they are even available), those preventive maintenance costs are an absolute bargain, /especially/ if you are doing the work yourself on your own time. Maybe it isn't much money in your world, especially when someone else is paying. I just priced the main power supply caps in one of my Cromemco systems and it comes to ~ $120 (and all special order of course); if I replaced all the caps in all my (working) systems as you and a few others are suggesting across the board regardless of the system, condition etc., it would easily exceed $2000 if I could even find suitable replacements. And what about those prone to explode tantalums while we're at it... If you're recapping 20-year old or newer circuit boards for customers as you apparently are then it does indeed often make sense to replace all the aluminum electrolytics, especially if the board has problems or there's visual evidence of failure, but let those of us with older, well-working systems use our _judgement_ whether to replace or not. OK? To each his own... that are running perfectly "just in case"... How do you -know- they are "running perfectly"? They reliably do what they're supposed to do. m
Re: MEM11 Update
Made a lot of progress today. I just wrote a "hello world" program and got it working so the UART output shows up on the simulator. Took a bit more work as there were a couple of subtle bugs lurking in paths I hadn't fully exercised previously (it's the nature of things). It was more complicated by the fact that this is the first time that the "timekeeping" code has been executed (when a character is sent over the simulated UART, a timer is set in the simulator that determines when to clear the transmit busy flag). That code had a few issues but it's all working well now. The way that the timekeeping code works is that time advances only as each instruction is executed. Therefor, you don't have to worry about time dependent code behaving poorly when instruction execution has halted (such as hitting a breakpoint). I also updated the code that generates the assembler listing so that the ALU instructions are fully decoded. Makes it much easier to figure out what's going on when I'm debugging the J1 code. The simple forth programs I was using prior to the "hello world" program didn't present too much of a problem but as the programs are becoming more complex, having a "reasonable" listing makes a world of difference. I also added the capability to "break" into a running program by entering a ^D on the keyboard. Not sure if I'll keep it as ^D or not but for now it allows me to interrupt the execution of the J1 program. It's useful when the code is looping and not hitting any of the set breakpoints. ;-) I have a few more things to try out with the UART (like character input) before I move on to testing out the simulated FRAM. TTFN - Guy On 7/20/15 2:04 PM, Guy Sotomayor wrote: As I mentioned previously, I took some time off from working on the MEM11 for the past several months. I had some time over the past few days, so I spent it working on the simulator. Right now all of the J1 instructions seem to simulate properly. Everything related to the basic simulator also seems to be functional. I still have work to do to write code for the simulated I/O (it's all stubbed out at the moment). The way that I'm implementing the I/O, is that it's pretty modular. All of the fundamental code structures are there, I just have to write the "handlers" for the particular I/O devices. I wrote the majority of the J1 simulator to be H/W agnostic (as far as the I/O is concerned), the I/O at this point will match what I expect to be in the actual MEM11 H/W. Here's what the simulator currently supports: - All command functionality is present and functional. These are the way that one interacts with the simulator. The commands include things like: - loading files into J1 memory or FRAM - dumping memory locations from J1 memory or FRAM - modifying memory locations in J1 memory or FRAM - setting, listing and clearing breakpoints - starting execution - single stepping execution - dumping the data & return stacks - starting and stopping instruction tracing - All of the J1 instructions now seem to execute correctly (lots of typo's and other subtle bugs) - Exceptions work now. This allows the J1 program to do something "silly" and the simulator won't crash (had enough of that already while I was debugging the simulator!). It'll report what the J1 program did that was "silly" (ie unaligned memory accesses, etc). - It also contains a reasonable "help" system. I've written an instruction test program that tests out all of the J1 instructions and it is "self checking". That is, it will throw an exception (unaligned address) if the result of the instruction test isn't what was expected. To determine what failed, I look at the address where the exception occurred and reference the test program listing to determine which test failed. I verified that it is indeed operating correctly by hand checking via the instruction trace file that it was doing the "right things". I had originally started debugging by single stepping through the program but after the test program grew to over a few dozen instructions, it became too tedious for me to ensure that I was accurately verifying the instruction execution. This is where the instruction trace file became invaluable. The next thing to do is to work on the simulated I/O. Once I'm confident that all of that is working then I can go about debugging all of the code I've already written for the MEM11 itself. The simulator should give me a pretty good environment for debugging, especially when compared to the actual HW. Oh, and of course everything (simulator, MEM11 firmware and tools for the build environment) are all written in forth. ;-) TTFN - Guy
Re: PDP 11 gear finally moved
On Tue, 21 Jul 2015, Mike Stein wrote: On Tue, 21 Jul 2015, Tothwolf wrote: On Tue, 21 Jul 2015, Mike Stein wrote: FWIW I'm certainly not about to spend 100s of dollars, not to mention time spent in sourcing and replacing, to replace the caps in systems 100s? Where are you sourcing your components from? The typical board I rebuild has a component cost of about $20 or less. Smaller switchmode PSUs with a bunch of 10-18mm radials might be closer to $35-50. Larger PSUs /might/ cost closer to $100 if they have several large screw terminal capacitors in them. All things considered, that isn't very much money in today's dollars, and considering the full replacement cost of some of these boards (if they are even available), those preventive maintenance costs are an absolute bargain, /especially/ if you are doing the work yourself on your own time. Maybe it isn't much money in your world, especially when someone else is paying. Like anyone else, I have to buy the parts I use for my own equipment. If someone else wants to volunteer to buy them for me, I'm certainly not going to argue though ;) I just priced the main power supply caps in one of my Cromemco systems and it comes to ~ $120 (and all special order of course); if I replaced all the caps in all my (working) systems as you and a few others are suggesting across the board regardless of the system, condition etc., it would easily exceed $2000 if I could even find suitable replacements. Without an actual list of components required and without knowing which vendors you are getting your price quotes from, I have no way to verify if your $120 total is representative of the norm. If your Cromemco system is still functioning to your satisfaction, and you have zero interest in replacing aluminum electrolytic capacitors as part of preventative maintenance, why are you even bothering to price them? I also seem to remember saying earlier in the thread: "In the odd case where a computer grade screw terminal capacitor is extremely expensive or completely unobtainable (those which I've purchased were under $20-30) I might be willing to leave an original part in place, *if* it can pass a leakage test." And what about those prone to explode tantalums while we're at it... Well, if you want to bring those up and expand on the list of "bad caps" I mentioned, early SMD solid tantalums seem to be quite problematic in terms of spontaneously shorting out and going up in flames, even when operated at half their rated voltage (as specified by the capacitor manufacturers). I can't say I've seen a higher failure rate with newer SMD tantalums than say modern SMD multilayer ceramics, however after having to scrape the remains of many charred SMD tantalums off of (unobtainium) boards undergoing repair, I can't say I really trust them. YMMV. If you're recapping 20-year old or newer circuit boards for customers as you apparently are then it does indeed often make sense to replace all the aluminum electrolytics, especially if the board has problems or there's visual evidence of failure, but let those of us with older, well-working systems use our _judgement_ whether to replace or not. OK? To each his own... I've previously done a great deal of commercial work (not now though), however I still do the very same work on my own equipment. I currently have somewhere north of 300 projects in my to-do queue (everything from modern stuff made a few years ago to test equipment and radios from the 1950s and earlier) which I've already purchased and kitted up parts for (of which I'd say about 2/3 are aluminum electrolytic capacitors). I know /exactly/ what *I* spent on my parts (I have it all organized in spreadsheets, just like I did for commercial projects), and my own parts costs do not at all seem to match up with what you are describing. I can also state from experience that the majority of capacitor failures (wear out; change in capacitance and increasing electrical leakage at working voltage) do not exhibit visual signs of failure or impending failure. The main exception are some of those really low quality far-east parts made in the last decade or so which manufactures use in consumer grade electronics. that are running perfectly "just in case"... How do you -know- they are "running perfectly"? [Just because a widget itself is functioning, you have no way of knowing if that capacitor is working 100% properly /unless/ you actually remove it from circuit and run a full battery of tests on it. Simply measuring the capacitance with a DMM while a capacitor is in circuit isn't good enough.] They reliably do what they're supposed to do. You didn't answer the question. How do you know those aluminum electrolytic capacitors are functioning just as good as they did when they were new? Unless you've tested them out of circuit, you simply cannot make that assertion. Just like the NiCd and SLA batteries I ment
Dumping Intel 43201 microcode ROM
Previously I posted photos of a Zilog Z8-02 MPD running a copy of the Z8671 BASIC subset ROM code on a breadboard. The Z8-02 was packaged in a ceramic leadless QUIP package, and I have only one good QUIP socket, so I made an adapter that the QUIP socket can plug into, which then has a very wide 64-DIP footprint for ease of prototyping. The bottom of the adapter has footprints for surface-mount decopling capacitors very close to all of the QUIP socket pins; the SMT capacitors are installed depending on the specifc chip for which the adapter is configured. Although the Z8-02 is totally unrelated to the Intel iAPX 432, this served as validation that I can make a usable QUIP socket adapter. The iAPX 432 General Data Processor consists of two chips, the 43201 instruction unit and the 43202 execution unit, both packaged in the ceramic leadless QUIP. Since I only have one QUIP socket, I plan to make sockets using pogo pins and a machined or 3d-printed frame. For now, I have just wired up the 43201 on a breadboard in microcode ROM dump mode, and captured the ROM contents using a logic analyzer. Photos: https://www.flickr.com/photos/22368471@N04/sets/72157653865063443 The 43201 has 4K words of 16 bits of vertical microcode ROM, however the top-level control is not done by the microcode ROM, but rather by a bunch of PLAs and hardwired logic. Many of the simpler 432 instructions are executed without use of the microcode ROM at all. Microcode routines are invoked in response to specific conditions or more complex instructions, and the routine entry addresses come from those PLAs, so it is fairly difficult to interpret the contents of the microcode ROM. While I can identify many of the entry points, I only have been able to determine what a few of them actually do, such as a few of the floating point instructions, and one of the simplest object instructions. However, eventually I hope that study of the ROM dump will shed some light on a few dark corners of the architecture left unspecified by the otherwise fairly comprehensive iAPX 432 General Data Processor Architecture Reference Manual. I have a design in progress for an iAPX 432 test system using a MicroZed board. This is based on the Xilinx Zynq, which has ARM Cortex-A9 processor hard cores as well as a substantial amount of FPGA fabric. The MicroZed will plug into my board, which will have level-shifters and such, as well as the QUIP sockets for the 43201 and 43202. The FPGA will be programmed to act as a memory controller for the 432 packet bus, as well as a logic analyzer for both that bus and the interchip bus used for microinstructions and status. There is not known to be any surviving coherent release of iAPX 432 software, so I'm developing my own software from scratch. It is a large task, because the iAPX 432 architecture is completely object-oriented (implemented by the microcode and hardware), and there have to be several dozen properly formed system objects in memory just to execute the simplest program. I expect that my first attempts to get the iAPX 432 to execute a code image I have generated will result in failure. The 432 architecture provides for a lot of software fault recovery, but if the system objects are not properly set up for the fault condition, it will assert the FATAL pin and halt. (This is the same concept as a double bus fault on more conventional processors.) By studying the bus activity leading up to the halt, I hope to be able to determine what problem with the memory image led to the halt.
resurrecting the Intel iAPX-432 32-bit microprocessor
I changed the subject line since unless you recognise 43201 others might not make the connection :-) > On 22 Jul 2015, at 4:18 pm, Eric Smith wrote: > now, I have just wired up the 43201 on a breadboard in microcode ROM > dump mode, and captured the ROM contents using a logic analyzer. > Photos: > >https://www.flickr.com/photos/22368471@N04/sets/72157653865063443 As someone who has held an interest in the iAPX 432 since it was released, this is an exciting development, thank you for sharing your intentions and progress. > The 43201 has 4K words of 16 bits of vertical microcode ROM, however > the top-level control is not done by the microcode ROM, but rather by > a bunch of PLAs and hardwired logic. Many of the simpler 432 > instructions are executed without use of the microcode ROM at all. Do you know if this was where the so-called “SiliconOS” was stored? was it simply mixed in with the regular instruction set? For others the SiliconOS provided quite high-level constructs like resource-scheduling (multi-tasking) and other operating system like functions, hence the name. > There is not known to be any surviving coherent release of iAPX 432 > software, so I'm developing my own software from scratch. I guess the other challenge with original iAPX 432 software, if I have this right, is how dependent it was on the iRMX-86 environment which was used to bootstrap iMAX? so effectively two operating systems needed to coexist with the supporting hardware, that is a lot of moving parts and presumably particular software pieces (with dependencies) that would need to be pulled together. On your website you mention you have some VAX VMS software that supported the iAPX 432? does this include any form of cross-compiler? have you tried to resurrect any of it? > It is a > large task, because the iAPX 432 architecture is completely > object-oriented (implemented by the microcode and hardware), and there > have to be several dozen properly formed system objects in memory just > to execute the simplest program. This is an interesting point of distinction between classes of machines. The Burroughs B5000 and B6000 families had a similar requirement in that they needed to be a formed execution environment, with the operating system to function; so dependent were they on having an OS which could respond to residency interrupts etc. Other system classes by comparison could be switched on, loaded with stand-alone object-code and do something useful (obvious examples being the PDP-8 and PDP-11). > By studying the bus > activity leading up to the halt, I hope to be able to determine what > problem with the memory image led to the halt. May your logical analyser capture all the needed events and your logic probe strike unerringly.
