Long story short, after a few months i decided to play a few games on my 6128+. i connected it to the TV with SCART cable and inserted the power plug, turned it on and the LED light blinked and i heard a popping sound. I turned the computer off, as i thought it could be a bad capacitor. Tried again and it was the same result. And then i realised, i plugged in the wrong PSU, not the correct one with 5V, but one with 12V. Polarity was actually ok.
So, did i kill it? What can i check? After powering on with correct PSU, there is only a yellow rectangle, with green border, no boot as it should be from cartridge (basic or burning rubber). Thank you for any suggestions.
You probably killed the ROM or some other chips. Yes overvoltage is a problem and you would need now to do a full analysis. Any chip could have burned or damaged. If that is the ASIC, your CPC is dead, as there is no replacement (other than salvaging another 6128+).
If that is ASIC, another one can find in GX4000.
Quote from: ZorrO on 15:43, 21 January 24If that is ASIC, another one can find in GX4000.
Desoldering and resoldering the ASIC from a GX isn't a task for that feint hearted though. Probably easier to just upgrade the GX to 128K if you reach that stage.
Can you please post a picture of the rectangle?
If this indicates that the CRTC (which is included in the ASIC) was initialised correctly, then it's more likely that you have fried some other IC than the ASIC. Did you try with another cartridge? If you fried the ROM, then another cartridge should work. If you still have problems with another cartrdige, the next most likely culprit would be RAM.
RAM tends to die first and protects the other ICs, so don't worry about the trickier parts until you've sorted that out.
It happened once to my machine (well, in my case it was -5V) and I ended up with a fried RAM chip. It was easy to find: power the machine on, and touch the various chips to find which one is getting very hot. If you find one, that's very likely the broken one.
Otherwise, more advanced techniques will be needed.
Anotherone of those threads where someone asks a question and never returns to answer any of the followups.