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PET 8032-32B How many chips should be missing on the m/b?

johnq

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Finally got my hands on a PET 8032-32B from a friend. He got it from someone else many years ago and from what I've been told it was last working but alas it's dead as a doornail now so am trying to revive it.

Before I go down the rabbit hole of troubleshooting, I'm new to the PET world (But not to the C64/VIC20). I've opened it up and on the motherboard I can see a lot of chips missing.

I"m wondering if this is supposed to be like this or have chips been pinched :(

The PCB part no. is 320350 Rev B. Can't seem to find a schematic for this, let along a component layout. None of the chips have references either which makes it difficult to troubleshoot :(

There are 16 chips missing on the top right - guess these are RAM chips. Maybe for a expansion?

Looks like there is also a regulator missing from the bottom left - the soldering all looks factory so am not sure if it's supposed to be missing?

Then there are another 7 chips missing from around the board.

Anyone know if it's supposed to be like this, as is there a schematic/component layout for this PCB. Hopefully if there are missing chips they can still be sourced.
 

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johnq

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Just after posting I think I found the layout:


Missing some important chips and even worse some idiot put the chips in the wrong location and backwards!! Agghh!!!

Looks like I'm in for the long haul fixing this one.

6522 and 6520 are missing but at least they are available (At a price)
ROM chips I can easily replace

Guessing the RAM chips also need populating.
 
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johnq

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I'm also wondering if the main board has been swapped from another machine?
Can anyone identify is this is all original parts?

PET 8032
Motherboard Assy 320351 E (PCB part no. is 320350 Rev B)

Also confusing is one of the ROM chips is a 901447-29
which according to the list is a editor ROM is for a Screen editor for BASIC 4, normal keyboard, no CRTC

No CRTC?! Is this ROM also incorrect?

It has the following ROMS - which also appear to be in the wrong locations:
901447-29
901447-10
901465-02
901465–20

The other ROMs are missing.
 

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Hutch

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Yeah, that's not an 8032 board. Looks like a 2001-N PCB.

Also looks like a mix of parts.
901465-02 is from Basic 3, 2001-N
901465-20 and 901447-29 are Basic 4

901447-10 is the character ROM which should be the same for most versions of the PET and it should be in socket F10

List of all ROM sets. http://penguincentral.com/retrocomputing/PET/petroms.pdf

Schematics are here FWIW. 320349 and 320351. There shouldn't be any significant difference on your 320350.

The missing "regulator" is actually a switching transistor for the cassette drive motor. And yeah, it should be there.
 
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daver2

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I am afraid you have a 'FrankenPET' there...

'It was working before' - Nah!

Yes, this is a 2001N machine - not an 8032.

The missing DRAM is 16 off 4116 devices. But (before you buy them and plug any (more) chips in), you need to test the voltage rails out.

I don't think there is a voltage regulator missing from this board.

There is no CRTC (Cathode Ray Tube Controller) chip with this board. The video display is all hard-coded in TTL logic chips.

UF10 (the character generator ROM) is missing, as is UD8 (the EDIT ROM).

UD3 missing is expected. This was an option ROM socket.

UG8 is a spare IC position - so that is fine.

The 6502 CPU appears to be in the wrong socket. It should be in UC4.

The ROMS are all screwed up as well. In the wrong place and a mixture of versions. I actually see the EDIT and character generator ROMs plugged in where they shouldn't be.

You can't mix and match different ROM BASIC chips (in general).

It looks like someone has taken all of the removable chips out of their sockets and put a random set back in it.

I would remove ALL of the socketed components (whether correct or not) and then seriously clean up the PCB.

Decide what ROMs you actually want in there (I would go for BASIC 4), and make a shopping list of the part numbers you require. Download the images and burn new EPROMs. We can tell you what types of EPROMs work later.

What type of keyboard have you got? This will determine the characters generator and EDIT ROM you require.

If you can burn EPROMS - you will need a copy of my PETTESTER.

Take heart - we have repaired PET boards that were in a worse condition that yours! It is also good that you have black IC sockets instead of white ones...

Dave
 
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Hutch

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Here's my 2001-N PCB (with Basic 4) for comparison and matching the chip locations.

1698524925028.png1698525074651.png
 
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johnq

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Noooo. A real frakenstein PET. :(

Is this doomed to failure now. I need a matching PCB for the 8032?
 

Hutch

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That's not good. Is that not going to work with the 8032 or can you mix and match?
No mix and match. The 2001-N is hard wired for 40 columns at 15KHz
The 80 col machines have a CRT controller chip and run at ~18KHz. The 12 inch monitors will only accept 18KHz.

You can replace the 6520 PIA chips with modern Western Design W65C21N6TPG-14
You could probably find a 6522 and or 6502 on EBay.
The RAM chips are 4116 DRAM and might be hard to source.

Have a look at the ROMULATOR or the Tynemouth RAM/ROM replacement board which will replace the 6502, the ROM and RAM.
But you'll still need the Character ROM, 6520 nd 6522 chips.
 
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Hutch

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Noooo. A real frakenstein PET. :(

Is this doomed to failure now. I need a matching PCB for the 8032?
8032 boards aren't too hard to find on Bay now and then.
Beware there is more than one version of the 8032 board and the "universal' board is marked 8032 but can be configured for 80 or 40 columns.
 
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Hutch

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Several 8032 boards on Ebay at the moment.

This is a real 8032 board. An early non-universal version. It appears to be complete and many of the chips have been socketed so there's been some work done to it.
A couple of the ROMs have been replaced by EPROMs

Here's an example of a universal board that is configured for 40 columns. So it's really a 4032 board.You can tell by the missing RAM chips in the middle of the boards.
It's also missing the edit ROM, Character ROM and the 6502.
 
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johnq

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I am afraid you have a 'FrankenPET' there...

'It was working before' - Nah!

Yes, this is a 2001N machine - not an 8032.

The missing DRAM is 16 off 4116 devices. But (before you buy them and plug any (more) chips in), you need to test the voltage rails out.

I don't think there is a voltage regulator missing from this board.

There is no CRTC (Cathode Ray Tube Controller) chip with this board. The video display is all hard-coded in TTL logic chips.

UF10 (the character generator ROM) is missing, as is UD8 (the EDIT ROM).

UD3 missing is expected. This was an option ROM socket.

UG8 is a spare IC position - so that is fine.

The 6502 CPU appears to be in the wrong socket. It should be in UC4.

The ROMS are all screwed up as well. In the wrong place and a mixture of versions. I actually see the EDIT and character generator ROMs plugged in where they shouldn't be.

You can't mix and match different ROM BASIC chips (in general).

It looks like someone has taken all of the removable chips out of their sockets and put a random set back in it.

I would remove ALL of the socketed components (whether correct or not) and then seriously clean up the PCB.

Decide what ROMs you actually want in there (I would go for BASIC 4), and make a shopping list of the part numbers you require. Download the images and burn new EPROMs. We can tell you what types of EPROMs work later.

What type of keyboard have you got? This will determine the characters generator and EDIT ROM you require.

If you can burn EPROMS - you will need a copy of my PETTESTER.

Take heart - we have repaired PET boards that were in a worse condition that yours! It is also good that you have black IC sockets instead of white ones...

Dave
Thanks for the detailed explanation. Getting the PCB to a working state doesn't sound like too much of a problem. The big problem I have is the mismatched CRT so will have to go hunting.
 

daver2

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Er yes. The 40/80 9" / 12" CRT will be a deal breaker I am afraid.

>>> Thanks for the detailed explanation.

No problem. That's what we are here for! You got a lot of concentrated detail in a few posts there...

Dave
 

johnq

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Always knew it was going to be a long term project. I'll keep on the lookout for a PCB and also a CRT - maybe the PET Gods will help and I"ll get both and can get 2 PET"s working :)
 

johnq

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I don't suppose anyone knows if there is a 8032 clone PCB available. I can find a clone PCB for the 2001 but nothing for the 8032.

For the price that these motherboards are going on eBay it might be cheaper (and lots more fun) to build one from scratch.

Are there any high res pics of a bareboned motherboard available - I'm happy to spend a few weeks doing the layout in KiCad as a education piece. Would be good to get this into a cad anyway for troubleshooting/preservation reasons.
 
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daver2

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Ah, so I pass you on my business trips up north.

I spent two years at Salford College of Technology and worked for the CEGB (as it was then) at Agecroft Training Centre.

Manchester was great - but I am lost now with all of the changes since my time. There was a brilliant little electronics shop in Salford - Spektrum Electronics if I remember correctly.

Dave
 
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