Not so much a repair log but a bit of information.
The system booted to either a blank screen, to a blue screen with a couple of bits of garbage or to a screen full of random garbage
Pulling the SID chip let the C64 boot normally.
I always pull the SID chip when starting out testing for this very reason. Not sure why it does it but it can cause problems like this.
Dumped some unprotected PALs from a broken Psycho Soldier board.
There are several empty PAL sockets on my board set and not sure where any of them go. There was also a PAL marked up as A6003-1 which MAME shows as being from Chopper. Not sure if this is also used in Psycho Soldier too but and info on this will be appreciated.
The PALs are:
A6003-1
A6004-2
A6004-3
As always with non working boards, these dumps are assumed working until im informed otherwise.
I recently won a Commodore 128 on eBay. It had no power supply and was therefore “untested”. In eBay terms this means its broken.
I know I shouldn’t have tried but in my haste I attempted to use my C64 supply. This resulted in one dead C64 power supply.
As the original C64 supply is pretty poor and a C128 supply is impossible to find for a decent price I thought I would build my own.
For a total cost of around £35 I bought a 5v power supply and a 9VAC transformer. Both of these are massively overspecced compared to the original and they will both fit into the case of my old “lightweight” Amiga power supply case.
I used the old Amiga lead as the connector for the C128 and reused the C64 lead from my newly burnt out supply to give me 2 separate outputs and it is capable of running both at the same time with room to spare.
Got a C128 off ebay for a decent price. Came with no power supply and sold as untested. This usually means its knackered and after building a power supply I can confirm it was indeed knackered.
First job, the visual inspection.
The C128 doesnt follow a standard IC orientation but the silkscreen is clearly marked.
Found one of the CIA chips in the wrong way.
I replaced this and carried on.
There was a bit of jumper wire running from JP7 to the Char ROM. From the schematics it looks like this is to set the char set between 128 and 64 mode.
I think this 128 was being used solely as a C64, what a waste. Fixed this to stock configuration.
Probing the Z80 there was no activity. Found the Z80 had no clock signal. Traced the clock from the VIC chip to a 74LS07 @ U60. All inputs were present but the outputs were missing. Replaced this to return the clocks.
Still no activity on the data bus.
Pulled the Z80 and tested, it was faulty. Replaced this.
Switched on and was greeted with a screen of garbage but the green border was now present. This can be a dead CIA so I swapped ICs U1 and U4 and the 128 booted straight into MONITOR mode and kept displaying DSAVE.
This can also be a symptom of a bad CIA so I fitted a known working one and it booted up to the 128 basic screen but the cursor was moving around on its own and some of the keys didn’t work. Looks like the other CIA is knackered too. Fitted another known good CIA and the 128 is fully working.
Dumped the unprotected PAL10L8 on my CVS motherboard. The board is not working but since the chip was unprotected im assuming its OK.