This is a replica PCB of the universal dynamic motherboard for the Commodore PET
The schematics were redone in KiCad and based off the original Commodore design. PCB is a near-exact replica (Or as close as I could reasonable make it) to the original Commodore PCB.
UNIVERSAL DYNAMIC PET
ASSY. NO. 8032089
FAB NO. 8032088
ARTWORK NO. 8032086 REV A
After purchasing what was advertised as an 8032 PET from eBay, I discovered that the motherboard was actually a 2001 board with random ROMs inserted. Considering the absurd prices for replacement PCBs I decided it would be a fun project to design and build a Universal dynamic PET board I could use with the CRT.
I spent several hours searching online, but no one appeared to have done a full CAD version of the schematics - and certainly no PCB layout (probably for good reason - it turned out to be a lot more work that I expected!).
The first task was recreating the schematics in KiCad. Fortunatel, the original Commodore schematics were available at zimmers.net, so while time consuming, it wasn't too difficult.
The next challenge was replicating the original PCB as closely as possible - especially hard without a physical board to reference. One of the members at the vcfed forums kindly provided high-resolution photos of the front and back of the board.
The original schematics for the Universal PET can be found here: https://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/univ/
The schematic and Gerber files were created in KiCad 9.
While tracing the original Commdore PCB and comparing it to the schematics, I came across a few design errors. These have all been corrected:
PCB:
- Removed GND VIA near UD14 pin6 - not connected
- Removed VIA to the right of R40 - not connected
- Removed GND VIA above C53 - not connected
- C37 shorted on PCB. Fixed.
- 12V test point near FB26/UD6 not labelled. Now labelled TP
Schematic:
- IEEE-488 Schematic - duplicate reference for C75. Now referenced as C98
- /EOI IN connects to J1 Pin 5, and not directly to J2 Pin 4
- J2 Pin 4 mislabelled as /EOI. Should be /EOI IN
- Cassette & Keyboard Schematic. UB2 should be labelled UB12
- UB12 Pin 8 should be /EOI, and not /EOI IN
To test the IEEE-488 bus, I would recommend reading PET and the IEEE 488 Bus by Eugene Fisher/ C.W.Jensen.
The book includes a BASIC program for testing the port.
If you building or troubleshooting a PET, I highly recommend using PETTESTER by daver2 at vcfed.
I couldn't have built and tested this without his PETTESTER ROM- it also helped my repair a few PETs along the way (along with numerous posts and advice from daver2)
If you'd like to purchase a bare PCB:
- UK buyers: Order from my store
- International buyers: Purchase via eBay, with shipping through eBay's Global Shipping Program.
This schematic and PCB design are shared in good faith and, to the best of my knowledge, are free of errors. However, I cannot guarantee their accuracy or reliability. Use them at your own risk - I accept no responsibility for any damage or malfunction from their use.
All original copyrights remain with their respective owners. This project includes elements created by others, and their rights are fully acknowledged and retained.