Commodore PET restoration - from rusty box of bits to glory

keanebg1

I've almost completed my restoration of this early, first gen Commodore Pet 2001-8.

Where we started:

Very rusty case, stuck keyboard, tape drive not looking great.

It’s an early 1977-1978 board with 2114 static ram and 6540 roms, lots of MOS ICs. MOS 6502 CPU, no video IC - video is generated entirely using 74xx logic. No audio, black and white only.

The PSU, fuse and regulators all checked ok - so powering it on brings the CRT to life, but its a totally garbled image.

keanebg1

Someones tried to reattach a leg on the character rom

The main board cleaned up well. PIAs and RAM removed.

Made in USA. Serial Number 1007890

10-10-20

Wah, that's a blast from the past!

Pull all of the socketed chips individually and reseat them. Dust off the PCB and then give it a clean with iso cleaner for any difficult spots.

keanebg1

CRT board. Almost no adjustments, only vertical size and brightness. I replaced some of the caps but not all as some still tested better than new ones, 40 year old Nichicons were very good quality. I changed out the 7812 regulator and several of the video transistors as well as resoldering all the larger joints.

keanebg1

About 2 months later the main board is all repaired and working again, the original roms were version 1.0. I replaced quite a lot of 74xx logic, all the 2114 SRAM, 3 of the 7 system ROMs as well as the character ROM. The 6540s are unobtainable nowadays so had to get rom converter boards made up by pcbway to use 2716 EPROMs in place. The original 6502 cpu, 6522 VIA, 6520 PIAs x2 are all still working. Keyboard had to be rebuilt & cleaned also.

keanebg1

Basic tape save and loading working….

keanebg1

Onto the upgrades…

Added SD2PET.. disk drive simulator. This came from TFW8B.

Added a RomRam board from Tynemount. This is a switchable Rom chooser with Basic 1.0,2 and V4.0 as well as a 32k ram replacement.

keanebg1

And finally I’ve made a small single transistor audio amp and attached to the custom audio cb2 output pin 19 on the second PIA and a piezzo speaker. Now we have sound!

Inviere

Fantastic work there, well done, great restoration 👍

o1s1n

Wow, this is amazing. Haven't seen someone restore one of these around these parts as of yet.

How's the CRT working? Anything been replaced on that? Looks lovely and bright for something from the 70s.

KeRbDoG

Man, the initial keyboards they used are just funky - guess they are repurposed cash register type keyboards?

keanebg1

https://youtu.be/6wIPJ_dIHmo

https://youtu.be/-Lvbxnqm4dQ

Playing 'Back to the Pet' Demo…

Fantastic.

keanebg1

https://www.boards.ie/discussion/comment/122682896#Comment_122682896

The CRT is fairly good & very bright, I have it turned down a lot. There is some horizontal linearity issues that come after about 10-15 mins but on the whole it's surprisingly good for something so old & simple. The main board generates 3x outputs for the CRT, both the 60hz and 15KHz H & V drives/pulse signals as well as the video itself.

keanebg1

https://www.boards.ie/discussion/comment/122683178#Comment_122683178

This was Commodore's first computer, I understand they were making a lot of calculators so had manufactures they turned to to make the same type keyboard… straight away in the next iteration PET 2001-N in 1979 they moved to a more normal Commodore QWERTY keyboard.

The Last Bandit

Fantasic work !! Great to see one of these brought back to life again

CiDeRmAn

For a minute there I thought Inviere had changed his username again!

Fantastic work though, well done