RE: Testing a 74S240

works. Sorry for the noise. Regards Rob > -Original Message- > From: Guy Dunphy > Sent: 01 May 2022 01:22 > To: r...@jarratt.me.uk; Rob Jarratt ; General > Discussion: On-Topic and Off-Topic Posts > Subject: Re: Testing a 74S240 > > At 11:25 PM 30/04/2022

Re: Testing a 74S240

At 11:25 PM 30/04/2022 +0100, you wrote: >In trying to fix my M7133 CPU from my 11/24 I thought I had identified a >failed 74S240. However, when I replaced it (while adding a socket), the >fault remained. So, I guess the original chip may not be faulty. I decided >to test the original chip on a bre

Re: Testing a 74S240

On 2022-04-30 19:25, Rob Jarratt via cctalk wrote: In trying to fix my M7133 CPU from my 11/24 I thought I had identified a failed 74S240. However, when I replaced it (while adding a socket), the fault remained. So, I guess the original chip may not be faulty. I decided to test the original chi

Re: Testing a 74S240

> On 04/30/2022 5:25 PM Rob Jarratt via cctalk wrote: > > > > I noticed that the chip (original and replacement) was drawing 100-110mA > from the bench PSU, which seems a bit high. > > > > I wondered if I might need a pull up resistor on the output, but my > understanding is that this i

Re: testing

> J > > -Original Message- > From: William Sudbrink > Sent: Thursday, March 10, 2022 4:29 PM > To: jw...@classiccmp.org; 'General Discussion: On-Topic and Off-Topic Posts' > > Subject: RE: testing > > ACK > > -Original Message- > From: c

RE: testing

n: On-Topic and Off-Topic Posts' Subject: RE: testing ACK -Original Message- From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of jwest--- via cctalk Sent: Thursday, March 10, 2022 5:29 PM To: 'General Discussion: On-Topic and Off-Topic Posts' Subject: testing

RE: testing

? -Original Message- From: cctalk On Behalf Of jwest--- via cctalk Sent: Thursday, March 10, 2022 2:29 PM To: 'General Discussion: On-Topic and Off-Topic Posts' Subject: testing Test test

Re: testing

FIN On Thu, 10 Mar 2022 at 22:30, William Sudbrink via cctalk wrote: > > ACK > > -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of jwest--- > via cctalk > Sent: Thursday, March 10, 2022 5:29 PM > To: 'General Discussion: On-Topic and Off-Topic Posts' >

RE: testing

ACK -Original Message- From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of jwest--- via cctalk Sent: Thursday, March 10, 2022 5:29 PM To: 'General Discussion: On-Topic and Off-Topic Posts' Subject: testing Test test -- This email has been checked for viruses by Avast anti

RE: Testing H745 Regulators

I found a 400V part on Mouser and ordered that. > -Original Message- > From: Jonathan Chapman > Sent: 18 February 2022 21:23 > To: r...@jarratt.me.uk; Rob Jarratt ; General > Discussion: On-Topic and Off-Topic Posts > Subject: RE: Testing H745 Regulators > > &g

RE: Testing H745 Regulators

> I always forget that the VAC is the RMS and not the peak-to-peak. I will > look for a minimum rating of 100V. 600V bridge modules are often more cost effective, and more likely to be in stock. That's why I went with the Vishay part I used. If you can't find what you need due to shortages, you

Re: Testing H745 Regulators

On 2022-Feb-17, at 11:40 PM, Rob Jarratt wrote: >> -Original Message- >> From: Brent Hilpert >> On 2022-Feb-17, at 2:38 PM, Rob Jarratt wrote: -Original Message- From: Brent Hilpert 20V on a 10 ohm load: current = 2A. 15V, 1.5A. In this regulat

RE: Testing H745 Regulators

> -Original Message- > From: Brent Hilpert > Sent: 18 February 2022 06:30 > To: r...@jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts > > Subject: Re: Testing H745 Regulators > > On 2022-Feb-17, at 2:38 PM, Rob Jarratt wrote: > >> ---

Re: Testing H745 Regulators

On 2022-Feb-17, at 2:38 PM, Rob Jarratt wrote: >> -Original Message- >> From: Brent Hilpert >> >> 20V on a 10 ohm load: current = 2A. >> 15V, 1.5A. >> >> In this regulator design there is no path for more current than that which >> the >> load draws, aside from temporary peak currents t

RE: Testing H745 Regulators

> Discussion: On-Topic and Off-Topic Posts > Subject: RE: Testing H745 Regulators > > I used a Vishay GBPC3506W-E4/51, which is 600V 35A, 400A inrush rated. > Looks like they're currently on-order at Mouser, I don't know about other > suppliers. > > The GBPC3506W

RE: Testing H745 Regulators

gt; > > -Original Message- > > > > > > From: Brent Hilpert bhilp...@shaw.ca > > > > > > Sent: 27 January 2022 03:33 > > > > > > To: r...@jarratt.me.uk; Rob Jarratt robert.jarr...@ntlworld.com; > > > > > &

RE: Testing H745 Regulators

m: Rob Jarratt > Sent: 17 February 2022 22:38 > To: 'Brent Hilpert' ; r...@jarratt.me.uk; 'General > Discussion: On-Topic and Off-Topic Posts' > Subject: RE: Testing H745 Regulators > > Sorry it has been a while responding. I have been looking further at my H74

RE: Testing H745 Regulators

3 > To: r...@jarratt.me.uk; Rob Jarratt ; General > Discussion: On-Topic and Off-Topic Posts > Subject: Re: Testing H745 Regulators > > On 2022-Jan-26, at 3:41 PM, Rob Jarratt via cctalk wrote: > > I am trying to test a couple of H745 regulators with a DC bench PSU > >

Re: Testing H745 Regulators

The guys at RICM have seen a problem with these supplies that if the output cap is bad it won't start switching properly. It goes into a mode where it acts as a linear regulator. As far as I remember they the a spice simulation that also indicated this when the output cap had low capacitance. Do y

Re: Testing H745 Regulators

On 2022-Jan-26, at 3:41 PM, Rob Jarratt via cctalk wrote: > I am trying to test a couple of H745 regulators with a DC bench PSU and I am > having some problems with testing them. > > My bench PSU is a twin unit so I can supply the +15V required as well as the > "AC" input using 20VDC from the othe

RE: Testing H745 Regulators

00:11 > > > > To: r...@jarratt.me.uk; Rob Jarratt robert.jarr...@ntlworld.com; General > > > > Discussion: On-Topic and Off-Topic Posts cctalk@classiccmp.org > > > > Subject: RE: Testing H745 Regulators > > > > Any chance you have a second supply yo

RE: Testing H745 Regulators

> -Original Message- > From: W2HX > Sent: 27 January 2022 00:11 > To: r...@jarratt.me.uk; Rob Jarratt ; General > Discussion: On-Topic and Off-Topic Posts > Subject: RE: Testing H745 Regulators > > Any chance you have a second supply you can parallel with the

RE: Testing H745 Regulators

Any chance you have a second supply you can parallel with the one you're using? Some bench supplies are dual supplies and have a parallel mode so you can benefit from both sides of the supply and they can track the same voltage. Or just put two supplies in parallel with the same voltage set on b

RE: Testing a H744 Regulator on The Bench

Subject: Re: Testing a H744 Regulator on The Bench Den tors 30 dec. 2021 kl 19:08 skrev Rob Jarratt via cctalk mailto:cctalk@classiccmp.org> >: Hello All, Following a discussion on resurrecting a PDP 11/45 I have started looking at the regulator bricks in the PSU. I have started

Re: Testing a H744 Regulator on The Bench

On 12/30/2021 10:08 AM, Rob Jarratt via cctalk wrote: Also, the indicator light does not work (as expected). I have seen the suggestion to replace it with a CM7381. It looks like these can be sourced with relative ease, b

Re: Testing a H744 Regulator on The Bench

Sounds like you're testing things basically the way I was: http://www.glitchwrks.com/2019/06/05/pdp1110-psu-repair I used a large Stancor 24 VAC transformer to supply power to the modules, since they usually see 20-30 VAC from the big transformer in the chassis. For dummy loads, I like automoti

Re: Testing a H744 Regulator on The Bench

Den tors 30 dec. 2021 kl 19:08 skrev Rob Jarratt via cctalk < cctalk@classiccmp.org>: > Hello All, > > > > Following a discussion on resurrecting a PDP 11/45 I have started looking > at > the regulator bricks in the PSU. I have started with a H744. I reformed the > three big capacitors, although t

Re: Testing bus transceivers

> From: Guy Sotomayor > A number of data books have circuits that were used to measure the > parameters .. so you might want to look at some of them Thanks for the tip! Alas, I don't know of any data books with circuits like that - any pointers? (And it's only the leakage current I ne

Re: Testing bus transceivers

Do you have any sort of precision, regulated, adjustable lab bench power supply that you could use to vary input voltage? If not, using a potentiometer as you mentioned would also work. Also, how many of these did you buy? If it's something like a dozen, manual testing will be practical. If it'

Re: Testing bus transceivers

On 11/16/15 8:21 AM, Noel Chiappa wrote: So, I have bought a number of DS8641 bus transceivers from a source in China, and cognizant of the claims that there are a lot of counterfeits coming from China, how can I test them to make sure the meet specs? I have a QBUS test board which I have cons

RE: Testing H7864 (MicroVAX II) PSU With No Load

> -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Robert > Jarratt > Sent: 02 November 2015 23:18 > To: 'General Discussion: On-Topic and Off-Topic Posts' > Subject: RE: Testing H7864 (MicroVAX II) PSU With No Load

RE: Testing H7864 (MicroVAX II) PSU With No Load

> -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Mattis Lind > Sent: 02 November 2015 21:44 > To: General Discussion: On-Topic and Off-Topic Posts > Subject: Re: Testing H7864 (MicroVAX II) PSU With No Load > > 2015-11-02 2

Re: Testing H7864 (MicroVAX II) PSU With No Load

2015-11-02 22:05 GMT+01:00 Robert Jarratt : > > > > I have just uploaded all the corrections. So the connector names on the > risers should now correspond. I have also corrected the area on the primary > control module around C403 and R407. > > Regards > > Rob > > Checked the new one. There are st

RE: Testing H7864 (MicroVAX II) PSU With No Load

> -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Robert > Jarratt > Sent: 02 November 2015 20:36 > To: 'General Discussion: On-Topic and Off-Topic Posts' > Subject: RE: Testing H7864 (MicroVAX II) PSU With No Load >

RE: Testing H7864 (MicroVAX II) PSU With No Load

> -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Mattis Lind > Sent: 02 November 2015 13:20 > To: General Discussion: On-Topic and Off-Topic Posts > Subject: Re: Testing H7864 (MicroVAX II) PSU With No Load > > 2015-11-01 1

Re: Testing H7864 (MicroVAX II) PSU With No Load

2015-11-01 17:35 GMT+01:00 Robert Jarratt : > > > > > > Maybe you can publish your schematic somwhere. It is much easier to > > > > come > > > up > > > > with ideas to pin point problems if we all view the same schematic. > > > > I > > > think it > > > > would be possible to identify the problem w

RE: Testing H7864 (MicroVAX II) PSU With No Load

> > Then you've not come across the ones in TK50Z desktop cases (and a few > other things). They don't like operating without a minimum load, No, probably not. Actually I may have one somewhere, but have never had to repair it, so have never run it without a load. Thanks for the warning though!

Re: Testing H7864 (MicroVAX II) PSU With No Load

On 01/11/2015 18:47, tony duell wrote: I've yet to find a DEC PSU that fails destructively if not loaded, it is more likely to just trip the overvoltaeg protection crowbar, shut down, then try to restart and repeat the cycle, tweeting as it goes Then you've not come across the ones in TK50Z des

RE: Testing H7864 (MicroVAX II) PSU With No Load

[Chopper transistor] > This one is a D905. I assume that's a 2SD905 (the '2S' is often left off the package). From the data I've seen that certainly could be used as a chopper transistor. -tony

RE: Testing H7864 (MicroVAX II) PSU With No Load

> > You mentioned DEC PSUs, this one is actually made by ASTEC. I will use a Firstly, every Astec PSU I've seen has been a swticher. They probably did make linear PSUs, but not common... Secodnly, it may have been made to a DEC design (rather than just a specification). I believe you replace

RE: Testing H7864 (MicroVAX II) PSU With No Load

> -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of tony duell > Sent: 01 November 2015 18:54 > To: General Discussion: On-Topic and Off-Topic Posts > Subject: RE: Testing H7864 (MicroVAX II) PSU With No Load > > > > Th

RE: Testing H7864 (MicroVAX II) PSU With No Load

> -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of tony duell > Sent: 01 November 2015 18:47 > To: General Discussion: On-Topic and Off-Topic Posts > Subject: RE: Testing H7864 (MicroVAX II) PSU With No Load > > > > >

RE: Testing H7864 (MicroVAX II) PSU With No Load

> That said, it's possible that there may be an auxiliary linear regulator in > there. That's common > for additional outputs with modest current needs, especially in older > designs where the > switching circuitry takes a lot of individual components. A TO-3 can isn't > what I would expect

RE: Testing H7864 (MicroVAX II) PSU With No Load

> > If it has a transistor at the primary side, and a high frequency transformer, > it's a switching supply. > Those want a load, usually. Especially the older ones. If there are large-ish electrolytics (100's of uF) with a voltage rating around 200V and no reason to believe that there is a

Re: Testing H7864 (MicroVAX II) PSU With No Load

> On Nov 1, 2015, at 12:37 PM, Robert Jarratt > wrote: > > ... > Hmmm Until your email I was pretty confident this was a switcher. But > your description of a linear PSU seems to fit. I have posted three photos of > the main board here: http://1drv.ms/1KQkTBp can you tell from that what kin

Re: Testing H7864 (MicroVAX II) PSU With No Load

its a switcher. On 11/1/2015 10:37 AM, Robert Jarratt wrote: > >> -Original Message- >> From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Paul > Koning >> Sent: 01 November 2015 16:52 >> To: General Discussion: On-Topic and Off-Topic Posts

RE: Testing H7864 (MicroVAX II) PSU With No Load

> -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Paul Koning > Sent: 01 November 2015 16:52 > To: General Discussion: On-Topic and Off-Topic Posts > Subject: Re: Testing H7864 (MicroVAX II) PSU With No Load > > > >

Re: Testing H7864 (MicroVAX II) PSU With No Load

> On Nov 1, 2015, at 7:12 AM, Robert Jarratt > wrote: > > Some of you may recall I have a faulty H7864 PSU, which failed a while ago > with a loud pop, but no obvious physical damage. I replaced the blown > transistor (on the primary side of the large transformer), but when I power > it on, th

RE: Testing H7864 (MicroVAX II) PSU With No Load

> > > Maybe you can publish your schematic somwhere. It is much easier to > > > come > > up > > > with ideas to pin point problems if we all view the same schematic. > > > I > > think it > > > would be possible to identify the problem without comparing the two > > > PSUs > > at > > > least in thi

Re: Testing H7864 (MicroVAX II) PSU With No Load

2015-11-01 15:04 GMT+01:00 Robert Jarratt : > > > > -Original Message- > > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Mattis > Lind > > Sent: 01 November 2015 12:46 > > To: General Discussion: On-Topic and Off-Topic Posts > >

RE: Testing H7864 (MicroVAX II) PSU With No Load

> -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Mattis Lind > Sent: 01 November 2015 12:46 > To: General Discussion: On-Topic and Off-Topic Posts > Subject: Re: Testing H7864 (MicroVAX II) PSU With No Load > > söndag 1 novem

Re: Testing H7864 (MicroVAX II) PSU With No Load

söndag 1 november 2015 skrev Robert Jarratt : > Some of you may recall I have a faulty H7864 PSU, which failed a while ago > with a loud pop, but no obvious physical damage. I replaced the blown > transistor (on the primary side of the large transformer), but when I power > it on, the transistor

Re: testing...

hmm. strange.. this seems to work. thanks for ignoring this. simon On 26-10-15 08:47, simon wrote: Please ignore. it seems my mail does not get through the last couple of times. -- Met vriendelijke Groet, Simon Claessen drukknop.nl

RE: Testing floppy drives

> I don't know if the guys at Accurite still have Drive Probe (a similar > product to AlignIt) in stock, but they seem to still be selling it: > > http://www.accurite.com/DriveProbe.html > I can tell you from experience that they do NOT. Basically, when you call them if they don't have it they f

Re: Testing floppy drives

A tool was published by Landmark called "Align It" and ran on MS-DOS. I don't know if you can find it, but it was a pretty decent tester and even provides a test log for each drive. I don't know if the guys at Accurite still have Drive Probe (a similar product to AlignIt) in stock, but they s

RE: Testing floppy drives

> You can normally do BETTER and more accurate alignment using an analog > alignment diskette (+ 20MHz dual trace scope), but I think that the > digital is "close enough". That is what was nice about the Microtest. It used the _analogue_ alignment disk but took the place of the 'scope and drive ex

Re: Testing floppy drives

On Thu, 28 May 2015, Alexandre Souza wrote: Howdy guys, greetings (as always) from Brazil! :o) I'm in a repairing spree! Got 5 (!) CP-500 (Brazilian TRS-80/III clone) to repair. All of them with single/double sided floppy drives, and the whole nine yards. Since it is not pratical to test

RE: Testing floppy drives

> Since it is not pratical to test all these drives on CP500, is there a > good software solution I can use on a PC for floppy drive testing? Something > that makes repairing easier? Long time I don't get so many drives to > repair/refurbish/align IMHO the ultimate PC drive exerciser was somet