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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 12th Apr 2021, 8:25 pm   #1581
ScottishColin
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Default Re: Non-working Commodore PET 3016

Well what you provided worked just fine for me - thanks again.

Colin.


Quote:
Originally Posted by Slothie View Post
Just a heads up, my diagnostic s/w was checking the wrong place for the stack. Luckily it wasn't a problem for Colin. Any further progress on this project I will move to a new thread when that happens!
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Old 12th Apr 2021, 10:56 pm   #1582
ortek_service
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by SiriusHardware View Post
Even with that mild bug your test firmware was instrumental in getting the machine this far and I'm grateful that you sidelined whatever you meant to be doing the other evening to knock that tweaked version up for us instead.

Although Daver2's test firmware is obviously quite advanced in terms of what it does, the way it stalled on the screen test might have had us a a little bit perplexed if we had not had your alternative which was able to go past that point.

I would imagine it is very hard to write a comprehensive test suite in 2K when you have the crippling limitation of not being able to use either RAM or subroutines, at least initially.
Testing of test software can be a bit difficult - as you need to induce deliberate hardware faults or have an emulator test harness that can simulate this.

Yes, the Daver2 one was currently designed to just loop back to writing the whole of the screen-RAM, as soon as it detected a read-back error.

And would have been nice if it had a timeout / skip on any keypress (providing keyboard does work on at least one key) to an attempt to write something (maybe multiple places) to the screen etc. regarding the error that was found - as it does with Main RAM test.
Although this still wouldn't be able to find whether it was RAM IC's or the buffers at fault, so still need to do some tracing of known signals through the circuitry. And having the ability to be able to produce a customised test-routine that can be dropped in quickly to do this is rather useful.

In retrospect, I think the read fault on the main uP-side buffer could have still been detected using the Daver2 code, being as the main buffer was always active wither reading or writing (so did in fact replicate the databus either side) - But would have been more difficult if it was an actual RAM IC fault.

And still not clear how good the built-in diagnostics are, that may require a lot more working even though they do display RAM data errors.
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Old 13th Apr 2021, 9:29 am   #1583
ScottishColin
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Default Re: Non-working Commodore PET 3016

For a short period of time, I ran the test team at Aviva. that was fun. Writing regression test scripts and testing for new errors introduced by new code/configurations.

It was always the test team's fault when they found defects too - you'd think the team that had written the code would have been grateful that defects didn't make production, but it wasn't often like that.

Colin.


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Originally Posted by ortek_service View Post
Quote:
Originally Posted by SiriusHardware View Post
Even with that mild bug your test firmware was instrumental in getting the machine this far and I'm grateful that you sidelined whatever you meant to be doing the other evening to knock that tweaked version up for us instead.

Although Daver2's test firmware is obviously quite advanced in terms of what it does, the way it stalled on the screen test might have had us a a little bit perplexed if we had not had your alternative which was able to go past that point.

I would imagine it is very hard to write a comprehensive test suite in 2K when you have the crippling limitation of not being able to use either RAM or subroutines, at least initially.
Testing of test software can be a bit difficult - as you need to induce deliberate hardware faults or have an emulator test harness that can simulate this.

Yes, the Daver2 one was currently designed to just loop back to writing the whole of the screen-RAM, as soon as it detected a read-back error.

And would have been nice if it had a timeout / skip on any keypress (providing keyboard does work on at least one key) to an attempt to write something (maybe multiple places) to the screen etc. regarding the error that was found - as it does with Main RAM test.
Although this still wouldn't be able to find whether it was RAM IC's or the buffers at fault, so still need to do some tracing of known signals through the circuitry. And having the ability to be able to produce a customised test-routine that can be dropped in quickly to do this is rather useful.

In retrospect, I think the read fault on the main uP-side buffer could have still been detected using the Daver2 code, being as the main buffer was always active wither reading or writing (so did in fact replicate the databus either side) - But would have been more difficult if it was an actual RAM IC fault.

And still not clear how good the built-in diagnostics are, that may require a lot more working even though they do display RAM data errors.
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Old 13th Apr 2021, 9:32 am   #1584
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Default Re: Non-working Commodore PET 3016

What's the consensus on the keyboard connections on the bottom of the keys please?

I have seen three options:

1) go over them with a pencil - this seems the least permanent fix
2) some kind of silver electrical fluid, like that used to (try to) mend heated rear windows
3) some kind of conductive rubber fluid/spray

I'm not clear which one is preferable.

Thanks.

Colin.
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Old 13th Apr 2021, 9:57 am   #1585
SiriusHardware
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Default Re: Non-working Commodore PET 3016

1) No, because it is loose conductive material which will end up deposited on the key contact fingers and hold keys permanently pressed. Just in the past week I have had two repairs where microprocessor boards had been disabled by someone who liked to press the reset button with a pencil. Result: PCB held permanently in reset by conductive graphite deposits.

2) No, because that sort of paint (meant for fixing PCB tracks) dries hard / brittle and will break up into fine conductive dust when it has been crushed a few dozen times, causing the same problem as above.

3) The least worst option because it is flexible and can take a bit of squashing. Not spray, because you can't control where it goes. It has to be paint, carefully applied with a fine brush. If you use that stuff you have to follow the instructions to the letter, in particular, you must mix it up properly and you must allow it to dry for the time specified.

I would try seeing if those dimples on the bottom of the key plungers can come off easily because if they do you have the option of trying to find an old PC keyboard which uses similar rubber-dimples-with-a-conductive-blob-attached.
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Old 13th Apr 2021, 1:21 pm   #1586
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Default Re: Non-working Commodore PET 3016

Thanks all - we now have a working keyboard.

About ten of the keys don't function but I think that's down to the individual key not making a circuit when it is pushed - off to investigate that now.

I certainly get a lot of the keys I didn't get before.

Colin.
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Old 13th Apr 2021, 1:26 pm   #1587
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Default Re: Non-working Commodore PET 3016

Glad that's one step further forward. Can you list the keys which are not working? If they are randomly distributed around the keyboard then maybe you do just have dead carbon contacts on those keys but if they are distributed along a particular row or column that could point to a cable / connector fault or another track eaten away on the keyboard PCB.
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Old 13th Apr 2021, 2:27 pm   #1588
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Default Re: Non-working Commodore PET 3016

OK - I've narrowed down the keys with problems to one trace. None of the keys attached to this trace work.

As far as I can see, the issue is in the (I'm sure these are the wrong words) jump trace on Pin I of the attached picture - the one that starts just below where the cable actually is and rejoins between \ and (.

I have continuity from one end of Wire I to the other. I have continuity from the solder point of wire I to just before the 'jump'. I have continuity from after the 'jump' to all of the affected keys.

I've attempted to circle it here. I believe that I should have continuity between the two ends of the jump - is that right?

Colin.
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Old 13th Apr 2021, 2:38 pm   #1589
SiriusHardware
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Default Re: Non-working Commodore PET 3016

I take it that's a 'found online' keyboard picture and not your actual one? Is there any chance you can post an image of the top centre portion of your actual keyboard PCB? And / or a link to where you found that image, because the forum engine has downsized it too much.
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Old 13th Apr 2021, 2:48 pm   #1590
ScottishColin
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Default Re: Non-working Commodore PET 3016

It came from here -does that link help?

http://www.zimmers.net/anonftp/pub/c...eyboardPCB.jpg

Colin.

Quote:
Originally Posted by SiriusHardware View Post
I take it that's a 'found online' keyboard picture and not your actual one? Is there any chance you can post an image of the top centre portion of your actual keyboard PCB? And / or a link to where you found that image, because the forum engine has downsized it too much.
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Old 13th Apr 2021, 2:52 pm   #1591
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Default Re: Non-working Commodore PET 3016

It helps to be able to see it at the larger size, yes. Back in a while, just wrapping things up here at work.
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Old 13th Apr 2021, 3:10 pm   #1592
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Default Re: Non-working Commodore PET 3016

Yes, you should have continuity between the brownish wire and the '(' pad on the left. via that jumper. The jumper looks like it has some kind of insulation printed over it, so it might be better to measure between the keyboard pad and the wire.
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Old 13th Apr 2021, 4:05 pm   #1593
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Default Re: Non-working Commodore PET 3016

The keys that do not work are all on one trace.

Here's a ZIP of my PCB.

I have continuity from the plug on the end of the wiring bundle to pin 1.

I have continuity from the solder joint of pin 1 to a carefully scraped area of the trace which I have circled in Red.

I have continuity from the other carefully scraped area of the trace which I have circled in Green to the relevant keypads.

I do not have continuity between the the Green circled trace and the Red circled trace.

Is it time for another carefully positioned wire between the two scraped off circled traces?

Colin.
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Old 13th Apr 2021, 4:16 pm   #1594
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Default Re: Non-working Commodore PET 3016

Can you measure for continuity between the three points I've marked on the attached diagram:

1 = 'I' wire solder joint
2 = '&' contact left side
3 = 'Left Bracket' contact left side

And state which of those three points are and are not connected together? Just trying to get an idea of exactly whether the break is to work out the best place to patch it, if necessary.

Can you also say whether - when the keyboard is assembled - the hole above-right of the backslash '\' key position has anything going through it, like a fixing screw / post, or whether it is empty / vacant?

Edit: Crossed with Colin's post above which I'm having a look at now.
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Old 13th Apr 2021, 4:22 pm   #1595
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Default Re: Non-working Commodore PET 3016

Quote:
Is it time for another carefully positioned wire between the two scraped off circled traces?
Yes, but bear in mind the positioning of whatever normally fits over the top of that area and keep your patch wire well away from the area immediately surrounding the contact areas so that the rubber plungers do not hit / disturb the the patch wire when the keys in that area are pressed.
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Old 13th Apr 2021, 5:04 pm   #1596
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Default Re: Non-working Commodore PET 3016

Are those links connected to the traces on the keyboard pcb using conductive adhesive?

I wonder if the connection can be made by putting a piece of paper over them and rubbing them down with a ballpoint pen on the paper, like letraset. Not sure if it would work or how long it might last.
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Old 13th Apr 2021, 5:10 pm   #1597
ScottishColin
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Default Re: Non-working Commodore PET 3016

Done it now - soldered a wire across the two circled areas and all the keys are now working. I suppose it's possible if the keyboard failed, then whoever owned it might have stopped using it then.

I have ordered Keypad Fix which will take a few days to get here.

Datasette next - I have muscle memory which told me how to get a file loaded (press Shift + Run/Stop).

For those who are interested, there's a postcode etched into the PET - LA9 5AY - which seems to be the Kendall College, so I reckon that's where it came from in the first place.

Colin.
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Old 13th Apr 2021, 6:01 pm   #1598
SiriusHardware
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Default Re: Non-working Commodore PET 3016

From the same post:

Quote:
All the keys are now working
Quote:
I have ordered Keypad Fix
??

I take it some of the keys are a bit 'dead', but do work if you press them harder?

Anyway, a good bit of troubleshoooting all round there, well done.

That postcode is an excellent signpost to the history of the machine, maybe someone who remembers having used it will eventually surface?

I happened to see Wonder Woman 2 (Wonder Woman 1984) the other night and there was a brief glimpse of a PET, didn't get which model, on an office desk - would they still have been in mainstream office use by then? I suppose the PC was still a little way into the future.
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Old 13th Apr 2021, 6:04 pm   #1599
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Default Re: Non-working Commodore PET 3016

Over the years I have caught glimpses of PETs in a number of films and TV sci-fi programs. I suppose the "futuristic" looks of the PET made them look in place in a lab or starship
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Old 13th Apr 2021, 6:07 pm   #1600
SiriusHardware
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Default Re: Non-working Commodore PET 3016

They are good looking machines even now, and you can't say that about many gadgets which were made 40+ years ago.
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