Yes I have a volt meter - I will check it out this weekend and hope it's nothing that can't be fixed in the meantime.

Many thanks for the long and informative post I will try what you recommend this weekend.. I followed the C128 diagnostic sheet but could see nothing on it that sounded similar to this issue.

However I bought (just out of hope) a 318020-03 and 251913-01 and replaced the ones in the C128 with no luck, I also transposed U1 and U4 once again with no change in C128s function (out of interest they were numbered 2085 and 2385).

Would it be worth buying a diagnostic cartridge for this issue - would it even work in your opinion?

I recently acquired a nice C128 and found a few quirks.

First it seems to work fine in C128 mode but GO64, CBM-key and power-on gives me the following screen:



Also whilst trying to use SPRDEF I get this:



When powered up with a C64 cartridge all I get is a black screen.

I've tried re-seating U32 and U33 but it made no difference.. would really love to get this working and not just give up on it.

All constructive advice welcome