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Old 5th Mar 2021, 12:59 pm   #801
SiriusHardware
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Default Re: Non-working Commodore PET 3016

At least that IC obviously was dud so we didn't waste your time or your money there. (Relieved). How many more, I have to wonder?

If you can now try looking for the signals I mentioned in #771, plus any that Mark may suggest when he surfaces later.
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Old 5th Mar 2021, 4:29 pm   #802
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Default Re: Non-working Commodore PET 3016

UH2/2, UG9/3 and UH6/12 give me 1Mhz square waves.

Nothing on UH6/3.

Nothing on UH9/12, 11, 9 or 8

UG9/6 and UH7/9 have the sameas each other - a 'longer' wave at 1Mhz.

Nothing on UH7/12.

Colin.


Quote:
Originally Posted by SiriusHardware View Post
Let's try following the timing chain for a while.

With all ICs inserted as normal, power on, please scope the following IC pins:

UH2 pin 2
UG9 pin 3
UH6 pin 12

You should have the same signal on all three of the above pins. If you don't even have a signal on UH2 pin 2, stop and report back.

Assuming you do, could you then look for further signals on

UH6 pin 3
UH9 pins 12, 9, 8, 11

UG9 pin 6
UH7 pin 9
(Both of the above two should be the same)

UH7 pin 12
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Old 5th Mar 2021, 6:01 pm   #803
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Default Re: Non-working Commodore PET 3016

You have activity on UH6 pin 12 but not on UH6 pin 3, correct? What about UH6 pin 2?

Also check voltage on UH6 pin 13 (should be high, steady ~5V).

Also check supply voltage to UH6 on pin 7 (0V supply pin, black lead) and pin 14 (+5V supply pin, red lead).
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Old 5th Mar 2021, 7:02 pm   #804
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Default Re: Non-working Commodore PET 3016

UH6/12 has the same waveforms and frequency as UH3 pins, but there's nothing on UH6/3, nor on UH6/2.

UH6/13 voltage is 5.00V.

UH6 voltage is 5.04V.

Colin.


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Originally Posted by SiriusHardware View Post
You have activity on UH6 pin 12 but not on UH6 pin 3, correct? What about UH6 pin 2?

Also check voltage on UH6 pin 13 (should be high, steady ~5V).

Also check supply voltage to UH6 on pin 7 (0V supply pin, black lead) and pin 14 (+5V supply pin, red lead).
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Old 5th Mar 2021, 7:15 pm   #805
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Default Re: Non-working Commodore PET 3016

Seems that UH6 is not working, the measurements that Sirius requested should confirm.

Before placing an order, lets see if we can verify some of the other parts of the circuit that should be independent of UH6.

UG1-8
UG1-11
UG7-6
UG7-12
UG10-11
UH10-11
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Old 5th Mar 2021, 7:36 pm   #806
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Default Re: Non-working Commodore PET 3016

OK - UG1/8 gives me a square(ish) - it's not beautiful - wave at 1Mhz.

None of the others listed give me any waveforms at all.

Colin.


Quote:
Originally Posted by Mark1960 View Post
Seems that UH6 is not working, the measurements that Sirius requested should confirm.

Before placing an order, lets see if we can verify some of the other parts of the circuit that should be independent of UH6.

UG1-8
UG1-11
UG7-6
UG7-12
UG10-11
UH10-11
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Old 5th Mar 2021, 7:50 pm   #807
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Default Re: Non-working Commodore PET 3016

Most of those outputs may be subject to / enabled by the states of the [PULLUP_2], [BA13 / BA14] and [NEXT] lines all of which come from off-sheet.

If we all agree that UH6 appears dead, it might save time to order

3 x 74LS107 (UH6, UH7, UH8)
1 x 74LS93 (UH9)
2x 74LS08 (UH10, UF1)
1 x 74LS74 (UG9)

Subject to their all being cheap enough, that is. At least they are all common 'LS' and not 'plain original' TTL.

If you just want to go slow and steady, then it certainly looks as though UH6 is dead, so I think you are going to have to replace that.

Last edited by SiriusHardware; 5th Mar 2021 at 8:01 pm.
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Old 5th Mar 2021, 8:09 pm   #808
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Default Re: Non-working Commodore PET 3016

Right. Ordered that lot along with sockets.

I'm (we're) going to get this thing working in the end. I have no idea what I'll do with it then but if/when it does work it'll be a good feeling to have rescued it.

I think I'll need to build a speaker for space invaders. I can remember doing that 40+ years ago.

Colin.
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Old 5th Mar 2021, 8:24 pm   #809
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Default Re: Non-working Commodore PET 3016

It seems we have the weekend off, unless the mighty Cricklewood can somehow manage to get those to you tomorrow.

When they do turn up we'll still continue with the same one-IC at-a-time approach, but at least the replace-and-try cycle will be a little bit shorter if you already have the other ICs poised and ready. In fact having them handy may be the best way of ensuring that you won't ever need them (...a variation of Sod's Law).

Of course you should replace UH6 first thing, since we are fairly sure that one is dud.
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Old 5th Mar 2021, 11:09 pm   #810
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Default Re: Non-working Commodore PET 3016

While we're waiting until Monday/Tuesday, here's where it started for me 41+ years ago. 1st December 1979, Eastern Daily Pres (Norwich based newspaper).

I'm not giving this one up.

Colin.
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Old 5th Mar 2021, 11:37 pm   #811
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Default Re: Non-working Commodore PET 3016

Great that you kept that all these years!

So what actually happened to your original PET?
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Old 5th Mar 2021, 11:47 pm   #812
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Default Re: Non-working Commodore PET 3016

Well the fuse at the back went a few times (2001-8), but in the end it wouldn't boot. So I can pick it to a computer repair place but they went bust. Never saw it again.

Colin.
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Old 5th Mar 2021, 11:59 pm   #813
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Default Re: Non-working Commodore PET 3016

Lovely story and such a shame to have lost the original PET but I can understand why you're keen to get this one working. Definitely making progress now.

Alan
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Old 6th Mar 2021, 12:00 am   #814
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Default Re: Non-working Commodore PET 3016

To be fair, I think Julie was suggesting something that worked alongside the original rather than completely replacing the electronics Hence the bit about being in time with the PETs pixel clock.
Strangely enough in my youth, inspired by the graphics add-on for the Research Machines 380z, I dreamed up a scheme to make a pixel-graphics mod for the PET that would overlay the text display by using the internal logic timing but connecting to 8k of RAM. It never got beyond the (graph) paper-and-pencil stage because I went off to uni and started playing with "big" computers, but I recon it would have been technically practical, even though it might not have been financially practical. Also things like the Acorn Atom did it better in colour and cheaper by then!
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Old 6th Mar 2021, 12:06 am   #815
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Default Re: Non-working Commodore PET 3016

Hmm, unlucky. I would have been inconsolable, I think. I wonder if it still exists somewhere now.

I should say that I have never physically laid hands on a PET, the closest I got to something of that kind / that era was a friend's Sharp MZ80K, although of course that was a very different (Z80 based) machine.

I do have a couple of complete (and when last tried, working) BBC model Bs but they were not originally mine, I bought them to 'rescue' them during the period when they were nearly worthless but I have never invested the time in them that I would have if I had owned one when they were at their zenith - at the time they were priced well beyond what I could afford. They are really nicely designed machines. That's as close as I have ever been to being a 6502 man, unfortunately.

I should really get those BBCs down and look them over but by all accounts they will need the RIFA capacitors changed before I could even think of turning them on now.
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Old 6th Mar 2021, 2:15 pm   #816
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Default Re: Non-working Commodore PET 3016

Several posts on Enhancing PET computers moved here :

https://www.vintage-radio.net/forum/...d.php?t=177421

Cheers

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Old 6th Mar 2021, 2:17 pm   #817
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by SiriusHardware View Post
Hmm, unlucky. I would have been inconsolable, I think. I wonder if it still exists somewhere now.

I should say that I have never physically laid hands on a PET, the closest I got to something of that kind / that era was a friend's Sharp MZ80K, although of course that was a very different (Z80 based) machine.

I do have a couple of complete (and when last tried, working) BBC model Bs but they were not originally mine, I bought them to 'rescue' them during the period when they were nearly worthless but I have never invested the time in them that I would have if I had owned one when they were at their zenith - at the time they were priced well beyond what I could afford. They are really nicely designed machines. That's as close as I have ever been to being a 6502 man, unfortunately.

I should really get those BBCs down and look them over but by all accounts they will need the RIFA capacitors changed before I could even think of turning them on now.


Yes, I once got 3 BBC's for 1 & also got a free Microvitec monitor from Radio Rallies. Whereas a Retro computer place is advertising a 'Refurbished' (aka a couple of RIFA caps changed in the PSU) system, plus a GOTEK drive for 400! I've still got my original Beeb, that I bought for over half that in the mid 80's - Second-hand, as the Beeb had been replaced by B+ / Master, which I ( / parent's) couldn't really afford. And I had to sell my original Spectrum + Microdrive etc. to buy it. So I only had a bit of assembler experience on the Z80 (Not too nice on the Spectrum, with having to reload assembler etc. after each crash), before switching to the Beeb's 6502.
This was rather useful for A-Level Electronics EPROM-Priogrammer project, writing the timing-critical bits in assembler, And also went with me to Uni, allowing some word-processing and a bit of coding on Acorn-Pascal etc.
6502 assembler's also been useful for later 680x / 68HC11 etc assembler, as it's not too dissimilar to 6502.
Those RIFA capacitors shouldn't actually stop it working, as they are just mains-filtering. And they don't tend to go short - just smoke a bit when the clear resin cases crack and let moisture into the Paper! dielectric. Surprisingly they still seem to sell the same ones, even though I've seen a whole bag of unused ones with cracked cases. So you could probably just snip them out for now, if they do smoke too much!


Back to PET's, we did have the odd one at school but only really got used during 'computer club' sessions, for playing games. And no-one could afford to have one of these at home, as it seems Commodore bumped up the price a lot in the UK (apparently had been selling them virtually at a loss in USA). By the time programming was taught, it was all on classrooms of Beebs.

So were rather lucky to win one (or two), given relative cost back then (But times have changed with regards to media publishing full names and address of Schoolchildren!)

But I got given a couple of PET's by people back in the 1990's, before much interest in retro computers, and I sold a 4000-series one that worked many years later, as took up too much space. But I've still got a 2001N with calculator keyboard and built-in cassette deck that I recall just displayed the infamous random characters on the screen. I'd started to look at checking the old unusual pinout RAM's (Someone did these on their AB Electronics IC Tester, with a bit of custom test writing for pinout), but hadn't got round to looking at the odd ROM's. So the posting of an adaptor board in the last few days looks interesting, although I'm keen to readout the originals to see what they're like / keep them if OK.
I did pick-up some PET PCB assemblies very cheap from a Radio rally years ago. But I think they were later more standard memory IC's designs, so would have to swap whole board, and thought that's cheating a bit
- Even if Commodore did often use upto 4 different boards seemingly random in many models!
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Old 6th Mar 2021, 8:28 pm   #818
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Default Re: Non-working Commodore PET 3016

It is a bit strange seeing my old home address in the newspaper column isn't it.

I won a 2001-8 for me and one for the school too, when our computing was limited to CESIL punched card turn-around from the City College in Norwich, or some pre-booked time on the teletype/acoustic coupler.

I'm old.

Colin.


Quote:
Originally Posted by ortek_service View Post
Quote:
Originally Posted by SiriusHardware View Post
Hmm, unlucky. I would have been inconsolable, I think. I wonder if it still exists somewhere now.

I should say that I have never physically laid hands on a PET, the closest I got to something of that kind / that era was a friend's Sharp MZ80K, although of course that was a very different (Z80 based) machine.

I do have a couple of complete (and when last tried, working) BBC model Bs but they were not originally mine, I bought them to 'rescue' them during the period when they were nearly worthless but I have never invested the time in them that I would have if I had owned one when they were at their zenith - at the time they were priced well beyond what I could afford. They are really nicely designed machines. That's as close as I have ever been to being a 6502 man, unfortunately.

I should really get those BBCs down and look them over but by all accounts they will need the RIFA capacitors changed before I could even think of turning them on now.


Yes, I once got 3 BBC's for 1 & also got a free Microvitec monitor from Radio Rallies. Whereas a Retro computer place is advertising a 'Refurbished' (aka a couple of RIFA caps changed in the PSU) system, plus a GOTEK drive for 400! I've still got my original Beeb, that I bought for over half that in the mid 80's - Second-hand, as the Beeb had been replaced by B+ / Master, which I ( / parent's) couldn't really afford. And I had to sell my original Spectrum + Microdrive etc. to buy it. So I only had a bit of assembler experience on the Z80 (Not too nice on the Spectrum, with having to reload assembler etc. after each crash), before switching to the Beeb's 6502.
This was rather useful for A-Level Electronics EPROM-Priogrammer project, writing the timing-critical bits in assembler, And also went with me to Uni, allowing some word-processing and a bit of coding on Acorn-Pascal etc.
6502 assembler's also been useful for later 680x / 68HC11 etc assembler, as it's not too dissimilar to 6502.
Those RIFA capacitors shouldn't actually stop it working, as they are just mains-filtering. And they don't tend to go short - just smoke a bit when the clear resin cases crack and let moisture into the Paper! dielectric. Surprisingly they still seem to sell the same ones, even though I've seen a whole bag of unused ones with cracked cases. So you could probably just snip them out for now, if they do smoke too much!


Back to PET's, we did have the odd one at school but only really got used during 'computer club' sessions, for playing games. And no-one could afford to have one of these at home, as it seems Commodore bumped up the price a lot in the UK (apparently had been selling them virtually at a loss in USA). By the time programming was taught, it was all on classrooms of Beebs.

So were rather lucky to win one (or two), given relative cost back then (But times have changed with regards to media publishing full names and address of Schoolchildren!)

But I got given a couple of PET's by people back in the 1990's, before much interest in retro computers, and I sold a 4000-series one that worked many years later, as took up too much space. But I've still got a 2001N with calculator keyboard and built-in cassette deck that I recall just displayed the infamous random characters on the screen. I'd started to look at checking the old unusual pinout RAM's (Someone did these on their AB Electronics IC Tester, with a bit of custom test writing for pinout), but hadn't got round to looking at the odd ROM's. So the posting of an adaptor board in the last few days looks interesting, although I'm keen to readout the originals to see what they're like / keep them if OK.
I did pick-up some PET PCB assemblies very cheap from a Radio rally years ago. But I think they were later more standard memory IC's designs, so would have to swap whole board, and thought that's cheating a bit
- Even if Commodore did often use upto 4 different boards seemingly random in many models!
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Old 6th Mar 2021, 8:29 pm   #819
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Default Re: Non-working Commodore PET 3016

I have three C2N tape drives that will need looking at. Anyone happen to know where to start?

Colin.
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Old 6th Mar 2021, 8:52 pm   #820
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Default Re: Non-working Commodore PET 3016

There is already some discussion about Commodore recorders in the other PET thread so you may find some useful advance information about them there. You'll need a working compatible Commodore computer (...VIC20?) to make any headway, perhaps you have one?

If you do, it might be best to start a separate thread about those.
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