Denial

you were right, thanks, the output from the Vic 20's is now good after checking on the crt i bought.

Thankyou all for the replies it was eventually found to be a bad 74ls133, I replaced that and got the computer working.

First of all, it's not the VIC-20 that switches between PAL and SECAM, it's your display which mistakes the video signal of your VIC-20 for SECAM for some of the time. Real SECAM output requires an adapter PCB in the VIC-20. Do you own a contemporary, "non-intelligent" CRT monitor to cros...

I have 4 Vic 20's two of which I had to repair, and those two, although working, switch between pal and secam output. the two that did not need any work do not switch signals.I have changed bad chips and recapped one of the two machines. Chips like the 6561 and 6502 etc, all check out okay with the ...

It's worth noting that 74LS series chips aren't as plentiful as they used to be, and unscrupulous dealers will sell you re-marked 74HC chips (or is it HCT?), claiming them to be LS. They'll often work for the job in hand, but you need the real thing occasionally, especially in crystal oscillator cl...

I have a composite to hdmi adapter that works with the working Vic 20's I have. vlcsnap-2024-01-06-18h04m59s801.jpg This is what I get on the Bad Vic 20 with a diagnostic/dead test cartridge inserted when turned on, (just a black screen without a cartridge), but if the computer is turned off and bac...

Don't suppose you could tell me where on the PCB L3 is could you? I can not find it to save my life. Found L1, L2, and L4 I only have one CR VIC, looking at the PCB I can't see an L3 either. Here's a shot near the power switch vic20-cr-switch.jpg Tracing the circuit I make out the pins as the follo...

[Getting better voltages from socket, but I dont know how to "hotwire" the switch to have it always on, for testing purposes, until I can get another switch. So there is no switch on the board. Any ideas, Thanks in Advance. We can ignore the 9V AC side for now, it's not required for the m...

I hate voltage drops - I have the same problem on a boombox I'm trying to repair. Only way I've found to trace them is to isolate parts of the upstream circuit by cutting traces and progressively re-introduce it back until you find the offending component(s). I am a "newbie" to this espec...

Can you tell me where "L5" is, as I can't locate it on the diagram or the board? It's actually L3, the writing is not too clear Screenshot_20231223_130641.png Have you checked P7 for wear? I had a board with intermittent power problems, replacing the socket fixed them. Cleaned and reseate...

According to the schematic L4 looks to be an inductor on the supply to the cassette motor http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/vic20/251027r2.gif I don't think it's involved in the +5V supply (but L5 is). If there's a voltage drop between the PSU and the motherboard I would f...

Try removing any socketed ICs to see if the voltage rises. Did it work before you re-capped it? Try some switch cleaner on the on/off rocker as well, perhaps there's a voltage drop across it. Removing chips did not increase the voltage and it shows the same black screen after recapping and have use...

I found a similar thread but it did not really answer my question, so I am posting my issue here. I power on the vic 20 and get a black screen, have tried swapping chips between this vic and another working vic and also re-capped the machine, but I still get the same issue. The voltage I am getting ...