Партнер-01.01 (Partner): Part 2 (Repair & boot)
15Case is looking a lot better - managed to scrub out most of the dirt from the top case so it looks much nicer - need to take a new thumbnail photo.
Keyboard still needs some work - maybe next video.
Did some troubleshooting - found that the 8080-clone (КР580ВМ80А or KR580VM80A) didn't have +12V on its pin 28.
From the schematic I could see that the +12V came from a regulator A1 ... a part called КРЕН8Д (equivalent to a LM7812). I measured an input voltage of around 18V and an output voltage of 1V ... the same as measured on the 8080-clone ... clearly not working.
The 2nd КРЕН8Д, regulator A2 on the schematic, appeared to be working okay ... it is responsible for the -5V (okay) and -12V voltages.
I decided to replace both with a modern equivalent - a PSU3-12 from ezsbc.com. The additional benefit is that we can do away with the heatsink.
Once installed, the machine booted! It took me by surprise. It appears that baseband composite is available on the board. The manual seems to indicate that modification to the modulator box is required ... although I am thinking that maybe the signal needs boosting (emitter follower?).
The video connector is a little weird - I didn't have anything that would connect to it so I replaced it with a 6-pin DIN (only thing I had handy). I created a simple 6-pin DIN plug to RCA plug which is working - planning to replace with a 5-pin DIN (different spacing) so I can simply re-use a VIC-20 A/V cable.
That's all for now. No idea how to use the machine - couldn't figure out how to boot BASIC. So next will be either working on the keyboard or getting BASIC to work, creating a cassette cable and trying to load some programs.
Documentation can be found here:
https://archive.org/details/partner-01-01-documentation
Software, ROMs, etc. can be found here:
https://github.com/alemorf/retro_computers/tree/master/Partner_01_01