On 9/2/21 2:32 PM, silverdr_at_wfmh.org.pl wrote: > > >> On 2021-09-02, at 14:08, Francesco Messineo <francesco.messineo_at_gmail.com> wrote: >> >>> Besides VIC itself? The ROMs and if they are present, the 65245 bus >>> buffers. The latter can be replaced by 74LS245. >>> >>> But I also had bad RAM, a bad LM323 voltage regulator and a bad 74LS138. >> >> I can add also (from real repairs): 6502 (very rarely, but happens), >> the 7402 on the clock generator, a 6522 jamming the databus. >>> >>> So dust off your scope and go hunting. >> >> that's the only good way. > > Sure. It's just that during my running the workshop time we practically had no VC-20s here. I barely recall repairing maybe two or three (don't remember now exactly but only a less than a handful for sure) over almost eleven years. Therefore I have no "feel" of what typical failures in those machines are. Shall find out eventually but starting at the most probable place statistically helps saving time. Thanks guys - off to vacuum cleaner ;-) Additional information: Die dead LM323 was still regulating, but only produced 3.xV on the output instead of 5V. It's only present on the old board which uses only 2114 RAMs. The dead RAM was on a new board (the one that can use a C64 PSU) and it was one of the two 6116. GerritReceived on 2021-09-02 15:00:40
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