I was gifted this C128 and I checked the PSU initially and everything seemed fine. but I just checked it again and the 5vdc is 4.5vdc now so i may have to get a PSU.
Anyways, it will boot to C128 mode and appears to be fine. Video signal is fine, i have a bit of a hum in the audio as i'm running composite into a CVBS to HDMI adapter.
but upon powering it up and holding down the C= key, i get a black screen with a tiny white line down the left side of the monitor..
resetting will go back into C128 mode.
Ram chips are not hot, checked the ram voltages and all are 4.5vdc which is probably too low but C128 mode works fine. I suspect it may be a bad u32 kernel rom and i've reseated every chip i can on the board.
Anything else I should check out? I have a diag cart coming in the mail and should be here sometime this week, the one from diychris.com
I don't see many troubleshooting and repair videos on the C128 so if any of you would be so kind as to produce some, that would be nice.. I may go into details on how to correct this once I get settled back in with the C128 once again, it's been since 1987 since i've touched one.
I think i'm going to get an EEPROM burner and try to just burn a kernel rom that way and I may do the others just for the heck of it. I want to try to get this rig as fresh as I can. The baord looks great, however I think some entropy has taken place in the ICs. The CPU and Z80 seem to be functioning correctly
Try a C64 game cartridge that doesn’t need the kernal. You may get that working, which would indicate a faulty ROM.
I had received a dead test cart from diychris, plugged it in and works fine. got the EEPROM programmer in, tried to read the u32 and while it reads, it comes up with a different checksum everytime so i'm gonna go on a wild guess the u32 rom is blasted. Got some blanks coming in from retroinnovations by wed and gonna give that a go soon. Thanks for all the help and i'll keep ya posted. Just documenting these things down so if someone else gets the same problem, they can see my steps.