Hi Dave
I'll have a read. Rom is in UD11
Just the 6 wires but the board itself plugs into one half/side of J9. There is a red wire that plugs into J4 pin 22 and blue into 20.
I can take more photos if you like?
| VCF Latam | Apr 24 - 26, 2026, | Bahía Blanca, Argentina |
| VCF Pac. NW | May 02 - 03, 2026, | Tukwila, WA |
| VCF Southwest | May 29 - 31, 2026, | Westin Dallas Fort Worth Airport |
| VCF Southeast | Aug 01 - 02, 2026, | Atlanta, GA |
| VCF West | Aug 01 - 02, 2026, | Mountain View, CA |
| VCF Midwest | Sep 12 - 13, 2026, | Schaumburg Convention Center, IL |
| VCF Montreal V2.0 | Nov 07 - 08, 2026, | Saint-Lambert, Montreal, Canada |
| VCF SoCal | See you in 2027, | Southern CA |
| VCF East | Apr TBD, 2027, | InfoAge, Wall, NJ |
-
Please review our updated Terms and Rules here
CBM 8032 for repair
- Thread starter Sarnian
- Start date
I'll have a read. Rom is in UD11
Just the 6 wires but the board itself plugs into one half/side of J9. There is a red wire that plugs into J4 pin 22 and blue into 20.
I can take more photos if you like?
daver2
10k Member
That makes more sense...
Have you tried pressing both buttons together then releasing the reset button first?
There is a diagnostic signal that is read just after the machine is reset. This causes the ROM to drop into TIM (the machine code monitor).
Dave
Have you tried pressing both buttons together then releasing the reset button first?
There is a diagnostic signal that is read just after the machine is reset. This causes the ROM to drop into TIM (the machine code monitor).
Dave
daver2
10k Member
I am a machine code programmer - so 20 hex passes!
That is TIM - the machine code monitor (as I thought - see post #42). Go and hunt down the Commodore manual for TIM.
As you have spotted - there are no buttons on a standard PET to reset it or to enter this useful machine code debug monitor that is present...
Hence the add-on board that adds the missing buttons!
The actual /DIAGnostic signal is shared with the internal sounder. So (I am guessing) when you operated the button that is connected to the /DIAG signal, it was disabling the audio output from the internal sounder - which was causing an audible click to be heard from the internal sounder.
The /DIAGnostic signal is only checked when the PET has just exited a reset condition - hence it requires both buttons to be depressed to start with, and then the reset button released.
I still have to look at the PCB. All of the above can be accomplished with two buttons - so I need to work out what the IC is for. There was a card (at some point) that reset the PET when you operated the DIAG button. I suspect this may be that card - but then we have to work out why pressing the DIAG button doesn't do what it should do...
Dave
That is TIM - the machine code monitor (as I thought - see post #42). Go and hunt down the Commodore manual for TIM.
As you have spotted - there are no buttons on a standard PET to reset it or to enter this useful machine code debug monitor that is present...
Hence the add-on board that adds the missing buttons!
The actual /DIAGnostic signal is shared with the internal sounder. So (I am guessing) when you operated the button that is connected to the /DIAG signal, it was disabling the audio output from the internal sounder - which was causing an audible click to be heard from the internal sounder.
The /DIAGnostic signal is only checked when the PET has just exited a reset condition - hence it requires both buttons to be depressed to start with, and then the reset button released.
I still have to look at the PCB. All of the above can be accomplished with two buttons - so I need to work out what the IC is for. There was a card (at some point) that reset the PET when you operated the DIAG button. I suspect this may be that card - but then we have to work out why pressing the DIAG button doesn't do what it should do...
Dave
Last edited:
daver2
10k Member
It looks like the on-board IC drives the connectors that are marked as /WRITE ENABLE on the rear of the little PCB. Assuming nothing is plugged into these 2*3 connectors, then it looks like the IC does nothing...
If the PAICS toolkit is plugged into ROM socket UD11 (starting address $A000), then try and enter the command "SYS 40960" from the keyboard to see what happens. If the PET crashes, that is not working as I thought it would... If you are greeted with a simple message, this indicates that the ROM is probably working - and you have the extra commands available to you described in the PAICS manual.
I will continue to study the little PCB...
Dave
If the PAICS toolkit is plugged into ROM socket UD11 (starting address $A000), then try and enter the command "SYS 40960" from the keyboard to see what happens. If the PET crashes, that is not working as I thought it would... If you are greeted with a simple message, this indicates that the ROM is probably working - and you have the extra commands available to you described in the PAICS manual.
I will continue to study the little PCB...
Dave
Thanks Dave
Nothing plugged into 2*3 connectors
Tried sys40960 and got the following
So on to phase 2, how do I get this bad boy working, I'm assuming its compatible with the CBM8032? If it is does, anyone know where I can buy or how I can make up a cable?
Also are these worth keeping, we don't have a cassette player and assuming these are all available to download in some archive?
Thanks Robert
Nothing plugged into 2*3 connectors
Tried sys40960 and got the following
So on to phase 2, how do I get this bad boy working, I'm assuming its compatible with the CBM8032? If it is does, anyone know where I can buy or how I can make up a cable?
Also are these worth keeping, we don't have a cassette player and assuming these are all available to download in some archive?
Thanks Robert
daver2
10k Member
So, the PAICS toolkit is working.
That ROM image (at that address) is something I have not seen archived. We could do with 'dumping' that ROM and getting it uploaded onto Bo's 'Zimmers' website.
Likewise with the tapes. Please don't bin them until you have had a chance of looking in the archives. It wouldn't surprise me if you had stuff there that wasn't archived.
You need an IEEE 488 cable - but a 'special' one designed for the PET. This cable has a PCB edge connector on the one end. You can still buy these...
Yes, the disk drive should work with the PET. The same procedure applies with the disk drive as the PET. Obtain the schematics, test for a good earth connection with the case, check the AC voltages from the transformer with it disconnected from the logic board, check the smoothing electrolytic capacitor(s) for short circuits, open circuits, leakage and capacitance value.
Power up the drive (disconnected from the PET), check for smoke signals... check the DC voltage rails for correctness. Finally, check the state of the 3 LEDs (power LED and the 2 drive select LEDs) when the drive powers up. These LEDs indicate the state of the Power On Self Test (POST) Codes.
That was a whistle-stop tour!
Don't forget that you can purchase a solid state disk add-on for the PET replacing the disk drive unit.
Dave
That ROM image (at that address) is something I have not seen archived. We could do with 'dumping' that ROM and getting it uploaded onto Bo's 'Zimmers' website.
Likewise with the tapes. Please don't bin them until you have had a chance of looking in the archives. It wouldn't surprise me if you had stuff there that wasn't archived.
You need an IEEE 488 cable - but a 'special' one designed for the PET. This cable has a PCB edge connector on the one end. You can still buy these...
Yes, the disk drive should work with the PET. The same procedure applies with the disk drive as the PET. Obtain the schematics, test for a good earth connection with the case, check the AC voltages from the transformer with it disconnected from the logic board, check the smoothing electrolytic capacitor(s) for short circuits, open circuits, leakage and capacitance value.
Power up the drive (disconnected from the PET), check for smoke signals... check the DC voltage rails for correctness. Finally, check the state of the 3 LEDs (power LED and the 2 drive select LEDs) when the drive powers up. These LEDs indicate the state of the Power On Self Test (POST) Codes.
That was a whistle-stop tour!
Don't forget that you can purchase a solid state disk add-on for the PET replacing the disk drive unit.
Dave
ScottishColin
Experienced Member
Please keep the tapes and if you get the time, upload their contents to somewhere - zimmers.net or archive.org (once it's available again for uploads). I don't see some of your cassettes available anywhere. I had some that were 40+ years old and I managed to read them all so you may be lucky.
In terms of cables, the Commodore PET used one to connect to disk drives or printers that had the ability to plug into the edge connector on the PET (see photos - Commodore part number 320101). These are getting harder to come by. It's probably easier (and cheaper) to buy an IEEE-488 cable with the larger D shaped connecters (Commodore part number 905080) at each end and make/use an adapter. There are several adapter designs available - I've made/used this one for example:
I've also got and repaired an 8050. It's worth bearing in mind that the disks that were meant for the 8050 are Quad density. These are harder to come by and a bit more expensive but they are still out there. I can use Double Density disks but only with about a 50% success rate.
Colin.
In terms of cables, the Commodore PET used one to connect to disk drives or printers that had the ability to plug into the edge connector on the PET (see photos - Commodore part number 320101). These are getting harder to come by. It's probably easier (and cheaper) to buy an IEEE-488 cable with the larger D shaped connecters (Commodore part number 905080) at each end and make/use an adapter. There are several adapter designs available - I've made/used this one for example:
I've also got and repaired an 8050. It's worth bearing in mind that the disks that were meant for the 8050 are Quad density. These are harder to come by and a bit more expensive but they are still out there. I can use Double Density disks but only with about a 50% success rate.
Colin.
Last edited:
Sent Bo a message
Tapes, guess I'm looking out for a cassette player now. How do you convert?
Do you know where I can buy a cable from?
Will test like we did for the CBM.
Solid state disk add-on, where can I buy one from?
Robert
ScottishColin
Experienced Member
There are several SD add-ons for the PET - I have the two below but there are more.
www.tfw8b.com
In order to save the contents of the tape, I simply LOAD each program from the tape using a datasette (commonly available at the usual auction web site), then SAVE the program directly to your SD add-on of choice. That then creates a file on the SD card that can be shared with others.
Plenty of 905080 style cables available at the same auction site - new ones seem to be still available if you don;t want to make one up yourself.
Colin.
SD2PET – Commodore PET – TFW8b.com
www.tfw8b.com
In order to save the contents of the tape, I simply LOAD each program from the tape using a datasette (commonly available at the usual auction web site), then SAVE the program directly to your SD add-on of choice. That then creates a file on the SD card that can be shared with others.
Plenty of 905080 style cables available at the same auction site - new ones seem to be still available if you don;t want to make one up yourself.
Colin.
Hi Colin
I've told the owner to keep the tapes. How do I upload / convert them?
I will look out for both cable and cable/adapter.
Robert
ScottishColin
Experienced Member
This is what have done in the past:
In order to save the contents of the tape, I simply LOAD each program from the tape using a datasette (commonly available at the usual auction web site), then SAVE the program directly to your SD add-on of choice. That then creates a file on the SD card that can be shared with others.
No conversion required.
When the file is SAVEd to the SD card add-on, you can remove the SD card from the add-on, plug it into a PC or Mac and that file should be able to be then shared with others - you could upload it here, or to one of the Facebook sites, to archive.org or email it to Bo and he will put it onto Zimmers if he doesn't already have it.
Colin.
In order to save the contents of the tape, I simply LOAD each program from the tape using a datasette (commonly available at the usual auction web site), then SAVE the program directly to your SD add-on of choice. That then creates a file on the SD card that can be shared with others.
No conversion required.
When the file is SAVEd to the SD card add-on, you can remove the SD card from the add-on, plug it into a PC or Mac and that file should be able to be then shared with others - you could upload it here, or to one of the Facebook sites, to archive.org or email it to Bo and he will put it onto Zimmers if he doesn't already have it.
Colin.
ScottishColin
Experienced Member
I have both. They both have advantages and disadvantages.
The bitfixer one for example is cheaper, but you have to put it together yourself. It doesn't have a case (although I designed one and put it on Thingiverse). It has the ability to plug cables onto the back of it if you want to attach other devices directly to the PET. It also has the ability to use files from your local netwok share if you wish so you don't have to keep removing/reinserting an SD card when you want to add or remove a program.
The SD2PET card is the easier one if you want to start there. It's only available made up so is a little more expensive and you cannot plug anything into the back of it, but it's very much plug-and-play.
The other one I have noticed (but I don't have) is the PETSD+ variant that with a 3D printer and a case can be made to look like an old Commodore hard disk drive.
GitHub - InsaneDruid/CBM-D9096: Cost- and feature-reduced version of the PetSD+ from Nils Eiler, designed specifically for headless operation in an external enclosure, connected with a true GPIB cable, similar to a 9060 or 9090.
Cost- and feature-reduced version of the PetSD+ from Nils Eiler, designed specifically for headless operation in an external enclosure, connected with a true GPIB cable, similar to a 9060 or 9090. ...
github.com
It depends what you're after. I have more than one type as I'm a bit of a collector and each do different things.
Colin.
Do like the SD2PET as it's nice and simple/clean but I've ordered the bitfixer one, as you pointed out you can plug other things in.I have both. They both have advantages and disadvantages.
The bitfixer one for example is cheaper, but you have to put it together yourself. It doesn't have a case (although I designed one and put it on Thingiverse). It has the ability to plug cables onto the back of it if you want to attach other devices directly to the PET. It also has the ability to use files from your local netwok share if you wish so you don't have to keep removing/reinserting an SD card when you want to add or remove a program.
The SD2PET card is the easier one if you want to start there. It's only available made up so is a little more expensive and you cannot plug anything into the back of it, but it's very much plug-and-play.
The other one I have noticed (but I don't have) is the PETSD+ variant that with a 3D printer and a case can be made to look like an old Commodore hard disk drive.
GitHub - InsaneDruid/CBM-D9096: Cost- and feature-reduced version of the PetSD+ from Nils Eiler, designed specifically for headless operation in an external enclosure, connected with a true GPIB cable, similar to a 9060 or 9090.
Cost- and feature-reduced version of the PetSD+ from Nils Eiler, designed specifically for headless operation in an external enclosure, connected with a true GPIB cable, similar to a 9060 or 9090. ...
It depends what you're after. I have more than one type as I'm a bit of a collector and each do different things.
Colin.
ScottishColin
Experienced Member
The only thing to bear in mind is:
1) you will need a cable with an edge connection if you want to add another device
2) every device on an IEEE 488 chain needs a unique identifier. Printers are normally 4, disk drives 8. You have to cut traces normally inside disk drives or printers to change their id.
With the bitfixer, you can make it (for example) id number 9 through a configuration file that you put on the SD card so you don't have to make hardware changes to attach other disk drives.
Colin.
ScottishColin
Experienced Member
Instructions are here:
github.com
Colin.
GitHub - bitfixer/petdisk-max: Firmware and schematics for the PETdisk MAX storage device for Commodore PET
Firmware and schematics for the PETdisk MAX storage device for Commodore PET - bitfixer/petdisk-max
github.com
Colin.
Hugo Holden
Veteran Member
I have an SD2PET, but right away I noticed that it hogged the GPIB connector on the PET, than I could not plug in other devices such as my SFD1001 drive and a printer interface I have, so I made what amounts to a double adapter, and the SD2PET then mounts vertically too, the details about it were on this old thread: