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Old 18th Oct 2021, 11:59 pm   #121
SiriusHardware
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Default Re: Commodore PET 2001 voltage regulators

Ok, got that thanks. I'll get to that tomorrow night.
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Old 19th Oct 2021, 11:11 am   #122
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Default Re: Commodore PET 2001 voltage regulators

The TAS250 complete with probes is a real bonus Tim. A good basic 'scope from a quality maker and learning to drive it should be much more straightforward than wrestling with a digital version.

In terms of what to do before the 'scope arrives the best advice I can offer is to undertake as much research as possible. Time spent studying PET documentation will be time well spent. As ever Bo Zimmerman's site in particular is an invaluable resource.

Alan
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Old 19th Oct 2021, 8:22 pm   #123
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Default Re: Commodore PET 2001 voltage regulators

The test EPROMs (2 x 2716) are programmed, I just need to rig an adaptor so that Slothie's can be plugged into the UD9 position. Probably do that at work tomorrow.
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Old 20th Oct 2021, 7:14 pm   #124
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Default Re: Commodore PET 2001 voltage regulators

Hi. Just a quick update. I took the board out today to remove the socketed chips and apply some contact cleaner to the sockets. This went fine, but I did notice that the chip in UD5 was very crusty (I've attached a picture). I had been very careful when removing the chips, and took UD5 out the same way as the others, but one leg is very loose. I'd be interested in hearing what you think about the chip.

In order to try and get some more information about it, I checked the schematics for the board version. It looks to have the description of '6332-120 ROM (B000-BFFF)', and in the notes next to it 'Replacement for 901465-19'; however, I can't find a reference to part number 901465-19 in the document.

Pending feedback, I was going to try and clean the chip, then potentially solder a new leg to the chip. I have not put the chip back in the PET for the moment, but with the other chips in place, we're still getting the same garbled screen as before.
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Old 20th Oct 2021, 7:36 pm   #125
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Default Re: Commodore PET 2001 voltage regulators

Quote:
Originally Posted by retromit View Post
Hi. Just a quick update. I took the board out today to remove the socketed chips and apply some contact cleaner to the sockets. This went fine, but I did notice that the chip in UD5 was very crusty (I've attached a picture). I had been very careful when removing the chips, and took UD5 out the same way as the others, but one leg is very loose. I'd be interested in hearing what you think about the chip.

In order to try and get some more information about it, I checked the schematics for the board version. It looks to have the description of '6332-120 ROM (B000-BFFF)', and in the notes next to it 'Replacement for 901465-19'; however, I can't find a reference to part number 901465-19 in the document.

Pending feedback, I was going to try and clean the chip, then potentially solder a new leg to the chip. I have not put the chip back in the PET for the moment, but with the other chips in place, we're still getting the same garbled screen as before.
901465-19 is one of the BASIC 4.0 ROM, it looks like your PET has been upgraded after manufacture to version 4. This version of BASIC had extra commands intended to support disk drives better. I think they may have been commands to list to printer etc. BASICs prior to 4.0 didn't have a ROM at B000-BFFF as far as I am aware, so its not surprising its not on the schematic.
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Old 20th Oct 2021, 7:41 pm   #126
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Default Re: Commodore PET 2001 voltage regulators

I can't (immediately) answer your question but in the PET we dealt with earlier, only UD6-UD9 were fitted. UD5 may contain some additional functionality or utility, maybe someone will spot what that ROM is for. Edit: Thanks Slothie - looks like that PROM does need to be in place and working.

Can you either take a good photo of PROMs UD6-UD9 fitted in their correct positions in the PCB (with the numbers on them clearly readable) or just tell us what the PROM ID numbers are in the form..

UD6 = xxxxxx-yy
UD7 = xxxxxx-yy

(etc)

I had ScottishColin's PROMs here briefly to check their contents, and by that time he had already had to restore a missing leg on his original UD6 - in his case he used a leg snipped off a preset resistor, but fellow forum member Timbucus later suggested grafting on a pin snipped off a dud or surplus chip in order to replace like with like.

If the whole pin is loose, that is, flapping around where the pin meets the body, then I'm afraid the chip has had it and will have to be replaced with a pin-compatible EPROM.

Normally if IC pins do snap, they snap where the narrow bit meets the wide bit, so if you take a whole leg (snipped off right next to the body) from another chip, you can solder the wide bit of the donated leg onto the wide bit of what's left of the chip leg.

Depending on your skill at soldering, you could try to solder the replacement leg to the inside of what's left of the old one, as per the attached rough sketch. That way the repair won't be visible once the IC is plugged back into its socket.
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Old 20th Oct 2021, 8:16 pm   #127
retromit
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Default Re: Commodore PET 2001 voltage regulators

Quote:
Originally Posted by SiriusHardware View Post
If the whole pin is loose, that is, flapping around where the pin meets the body, then I'm afraid the chip has had it and will have to be replaced with a pin-compatible EPROM.
This is, unfortunately, what the state of the chip is. The rest are all fine, just the one in UD5 which seemed very crusty/corroded. Looking over the chip again, it seems as if there is another leg on the other side of the chip going the same way. I'm just wondering if it has been badly corroded.
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Old 20th Oct 2021, 8:25 pm   #128
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Default Re: Commodore PET 2001 voltage regulators

I've had a look over the chips in UD6 to UD9. I've tried to take a couple of pictures (attached), but UD7/6 are particularly hard to read. Here's the details from the chips (all printed from the top):

UD9 = MOS MPS 901465 003 2279
UD8 = MOS MPS 901447 24 1079
UD7 = MOS MPS 901465 002 2179
UD6 = MOS MPS 901455 01 2179

I've looked back over the schematic documentation, and it looks to have the following assigned for the model of the PET:

UD9 = 901465-22
UD8 = 901447-29 or 901474-02
UD7 = 901465-21
UD6 = 901465-20

So they seem to match bar UD6 - this could be down to the poor print on the chip, or more likely, my poor eyesight.
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Old 20th Oct 2021, 9:33 pm   #129
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Default Re: Commodore PET 2001 voltage regulators

According to this list: http://mhv.bplaced.net/cbmroms/cbmroms.php

UD9 = MOS MPS 901465 003 2279 PET Kernal 3 F000-FFFF
UD8 = MOS MPS 901447 24 1079 PET Edit 3 40 N NoCRTC E000-E7FF
UD7 = MOS MPS 901465 002 2179 PET Basic 3 $D000-DFFF
UD6 = MOS MPS 901465 (was 1455?) 01 2179 PET Basic 3 C000-CFFF

>>I've looked back over the schematic documentation, and it looks to have the following assigned for the model of the PET:

UD9 = 901465-22 PET Kernal 4 F000-FFFF
UD8 = 901447-29 or 901474-02 'PET Edit 4 40 N NoCRTC' or 'PET Edit 4 40 B NoCRTC' Depending on Normal or Business keyboard
UD7 = 901465-21 PET Basic 4 D000-DFFF
UD6 = 901465-20 PET Basic 4 C000-CFFF

Earlier when I mentioned Basic 4 - ignore that, I got confused. I thought you were quoting the number on the chip not on the schematic. Looks like the schematic is for a version with basic 4.
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Old 20th Oct 2021, 11:03 pm   #130
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Default Re: Commodore PET 2001 voltage regulators

Looking through the info on the firmware section of Bob Zimmerman's site here:-

http://www.zimmers.net/anonftp/pub/c...pet/index.html

You have:

UD6 = 901465-01 ;BASIC 2 ROM 1 #
UD7 = 901465-0(02)? ;BASIC 2 ROM 2
UD8 = 901447-24 ;'Edit' PROM for BASIC 2 'N'
UD9 = 901465-003 ;Kernel PROM

# You've read the number on yours as 901455, more likely to be 901465 like UD7 and UD9

Here's the thing though - If you have 901465-01/02/003 PROMs fitted in UD6, UD7, UD9 positions you shouldn't need a BASIC 4 PROM in the UD5 position, so I don't know what's going on there.

Quote:
basic-4-b000.901465-19.bin
BASIC 4 ROM, original version
Remembering back, I think ScottishColin's BASIC 2 PET also came with an unidentified extra PROM which wasn't needed to get the machine running.

I acknowledge Slothie's info suggesting that the machine may have BASIC 3 according to his source, however the zimmerman site has all of the BASIC 3 ROMs beginning with part number 901447 or 901439.
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Old 20th Oct 2021, 11:32 pm   #131
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Default Re: Commodore PET 2001 voltage regulators

Quote:
Originally Posted by SiriusHardware View Post
I acknowledge Slothie's info suggesting that the machine may have BASIC 3 according to his source, however the zimmerman site has all of the BASIC 3 ROMs beginning with part number 901447 or 901439.
I think that might be a minor confusion, some sources seem to count the ROMS in the original PET with "*** COMMODORE BASIC ***" startup message as BASIC 1, and others as BASIC 2. So they list the versions of BASIC for the PET as BASIC1,2 and 3 or BASIC 2,3, and 4 depending on which convention the stick to. I think I'm inclined to trust the zimmerman site more, the link I gave was from my google bookmarks, I don't know when I bookmarked it.
If I've confused things, sorry!
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Old 20th Oct 2021, 11:45 pm   #132
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Default Re: Commodore PET 2001 voltage regulators

I think the bottom line is that the machine has definitely worked with all five PROMs fitted. The question is, does it really need that extra ROM in UD5 position when UD6 to UD9 are the standard four-PROM set for a BASIC 2 PET? And if not, why was it fitted?

I think in ScottishColin's case an extra PROM (unidentified / unidentifiable) came with his machine but was not fitted in it - maybe Colin can confirm.

If we can get the machine to the point where it will run Daver2's test code, one of the things that does is to display checksums of UD6, UD7, UD9, so at that point we would be able to confirm that they are what they seem to be.
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Old 21st Oct 2021, 11:20 am   #133
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Default Re: Commodore PET 2001 voltage regulators

I've just checked my photos from 2012 when I first got it (I'm still away on holiday) and the random PROM was plugged into UD4. It's not plugged in now and I don't think we ever identified what it was or even if it still contained any code.

Photos if you want to look at it now are here:

https://colinjhaynes.wordpress.com/2...6-restoration/

Colin.


Quote:
Originally Posted by SiriusHardware View Post
I think the bottom line is that the machine has definitely worked with all five PROMs fitted. The question is, does it really need that extra ROM in UD5 position when UD6 to UD9 are the standard four-PROM set for a BASIC 2 PET? And if not, why was it fitted?

I think in ScottishColin's case an extra PROM (unidentified / unidentifiable) came with his machine but was not fitted in it - maybe Colin can confirm.

If we can get the machine to the point where it will run Daver2's test code, one of the things that does is to display checksums of UD6, UD7, UD9, so at that point we would be able to confirm that they are what they seem to be.
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Old 21st Oct 2021, 12:24 pm   #134
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Default Re: Commodore PET 2001 voltage regulators

Quote:
Originally Posted by SiriusHardware View Post
I think the bottom line is that the machine has definitely worked with all five PROMs fitted. The question is, does it really need that extra ROM in UD5 position when UD6 to UD9 are the standard four-PROM set for a BASIC 2 PET? And if not, why was it fitted?

I think in ScottishColin's case an extra PROM (unidentified / unidentifiable) came with his machine but was not fitted in it - maybe Colin can confirm.

If we can get the machine to the point where it will run Daver2's test code, one of the things that does is to display checksums of UD6, UD7, UD9, so at that point we would be able to confirm that they are what they seem to be.
There were a number of add-on ROMS published for the PET that extended BASIC, maybe thats one of them. Has Tim told us what markings there are on the chip in UD5, I had a quick look back and he only seems to have told us what his schematic says, rather than whats on the actual chip.
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Old 21st Oct 2021, 12:29 pm   #135
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Default Re: Commodore PET 2001 voltage regulators

It would appear that you don't need anything in D3, D4 or D5 for the PET to work. The correct PROMs seem to be fitted to D6, D7, D8 & D9 (post #128) so I'd just proceed without the IC with badly corroded pins and worry about it later if needs be.

Alan
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Old 21st Oct 2021, 12:46 pm   #136
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Default Re: Commodore PET 2001 voltage regulators

Agree, I suppose it's lucky that it happened to be that one which the legs fell off and not one of the other four.

I actually thought Tim had told us the number written on the extra chip (901465-19, which would make it the first of three BASIC 4 PROMs) in #124 but that was a false memory of mine so we still don't know what the xxxxxx-yy ID of that PROM, the one which was fitted in UD5, actually is.
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Old 21st Oct 2021, 1:09 pm   #137
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Default Re: Commodore PET 2001 voltage regulators

Quote:
Originally Posted by SiriusHardware View Post
Agree, I suppose it's lucky that it happened to be that one which the legs fell off and not one of the other four.

I actually thought Tim had told us the number written on the extra chip (901465-19, which would make it the first of three BASIC 4 PROMs) in #124 but that was a false memory of mine so we still don't know what the xxxxxx-yy ID of that PROM, the one which was fitted in UD5, actually is.
No, he said
Quote:
In order to try and get some more information about it, I checked the schematics for the board version. It looks to have the description of '6332-120 ROM (B000-BFFF)', and in the notes next to it 'Replacement for 901465-19'; however, I can't find a reference to part number 901465-19 in the document.
. Thats why I initially went on about BASIC4 because I didn't notice he was talking about the schematic not the actual ROM.
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Old 21st Oct 2021, 2:22 pm   #138
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Default Re: Commodore PET 2001 voltage regulators

Yes - in fact if the machine did have BASIC 4, 901465-19 is exactly the PROM which would be fitted in UD5 position. I think we both misread Tim's post and jumped the gun a bit.

We seem to be agreed that the remaining four PROMs are the correct ones and the only ones required in a BASIC 2 machine, so for the moment, Tim doesn't need to worry too much about that failed chip.

ScottishColin, thanks for the link to the photos.
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Old 21st Oct 2021, 4:08 pm   #139
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Default Re: Commodore PET 2001 voltage regulators

Quote:
Originally Posted by SiriusHardware View Post
Looking through the info on the firmware section of Bob Zimmerman's site here:-

http://www.zimmers.net/anonftp/pub/c...pet/index.html

You have:

UD6 = 901465-01 ;BASIC 2 ROM 1 #
UD7 = 901465-0(02)? ;BASIC 2 ROM 2
UD8 = 901447-24 ;'Edit' PROM for BASIC 2 'N'
UD9 = 901465-003 ;Kernel PROM

# You've read the number on yours as 901455, more likely to be 901465 like UD7 and UD9

Here's the thing though - If you have 901465-01/02/003 PROMs fitted in UD6, UD7, UD9 positions you shouldn't need a BASIC 4 PROM in the UD5 position, so I don't know what's going on there.

Quote:
basic-4-b000.901465-19.bin
BASIC 4 ROM, original version
Remembering back, I think ScottishColin's BASIC 2 PET also came with an unidentified extra PROM which wasn't needed to get the machine running.

I acknowledge Slothie's info suggesting that the machine may have BASIC 3 according to his source, however the zimmerman site has all of the BASIC 3 ROMs beginning with part number 901447 or 901439.
Yes, I think it's a typo/mis-read on my part. Having looked at the IC again in daylight (althougth the printing is still poor), I think you're right in that UD6 should be 901465.
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Old 21st Oct 2021, 4:15 pm   #140
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Default Re: Commodore PET 2001 voltage regulators

Quote:
Originally Posted by SiriusHardware View Post
Yes - in fact if the machine did have BASIC 4, 901465-19 is exactly the PROM which would be fitted in UD5 position. I think we both misread Tim's post and jumped the gun a bit.

We seem to be agreed that the remaining four PROMs are the correct ones and the only ones required in a BASIC 2 machine, so for the moment, Tim doesn't need to worry too much about that failed chip.

ScottishColin, thanks for the link to the photos.
Apologies for any confusion - and I should have given the details off the top of the chip rather than just the schematic details!

From the chip we have the following:

ST 7943E C48179 T2590

I had a look over Google for any details, and it seems to be related to the PET BASIC programmers toolkit. I managed to find the manual for it online, and in the documentation it details the 4 main PET PROMS, then the location of the toolkit ROM which should be UD5. So it looks (to me) as if the previous owner had this ROM, and why it was found in UD5.

On looking over another post for the chip, the OP had a similar issue to me in that the chip was very corroded with the legs falling off; which is a real shame. I wonder if there was an issue with these chips? I'm just pleased that the four main PROMS all seem okay.

So hopefully that's one mystery solved!

Tim.
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