Denial

I came across this video on how to improve operation of the switch:

https://www.youtube.com/watch?v=6THVvOi64fM

Everything is working now!! But I don't know why :) I have two VIC-20's, board A and board B. When I bought board B and plugged it in, there was no picture. I get a picture if I swap the VIC 6560-101 from board A into board B. However, board B has the issue with reverse characters and cursor that bl...

Swapping 74LS138 at UC4 didn't help. I think its a RAM issue. I found this post about changing the location of screen memory: http://sleepingelephant.com/~sleeping/ipw-web/bulletin/bb/viewtopic.php?p=5511&sid=cadb342a77b6c342ebc466ce2bd30f98#p5511 I tried different locations from $1200 to $1E00 ...

Looks like VA10 also goes to a 74LS138 at UC4 on Pin 1 - I also have continuity with rest of VA10 there. This is a chip I haven't tried swapping.

I wanted to check that BD7 (bit 7 of the VIC side of the data bus) reliably appears at VIC when sent from the 6502 over the '245. At this stage, I'd take the entire mainboard trace of BD7 under extreme scrutiny - continuity, shorts to other traces, any cold solder joints, checking all socket pins. ...

Yes, the LP-560 is the very one I have, and it works great for checking pin states. I have an oscilloscope, but I prefer using the logic probe for checking signals, because of the audio cues. I connect the power clips to pins 1 and 2 of the cassette port. chysn, having a hard time knowing when I sh...

If available, I'd check the signal on BD7 with a scope at the '245, VIC, VIAs, RAMs. What are your thoughts on using something like a Elenco LP-560 logic probe to check these signals? I was thinking of picking one up just to learn how to use it. More easier though would be moving VIC and CPU over t...

None of the RAM chips get hot, and when I run that program I get a light-blue background within a blue border. No flashing or all blue screen (I can still read the text). I was curious what you were up to and found this page: https://www.atarimagazines.com/compute/issue20/202_1_VIC_Color_Tips.php Se...

With your multimeter and the VIC switched off, can you check continuity of VA10 between VIC Pin 31, UD7 (Char-ROM) Pin 19 and UE8 ('245) Pin 16 (all three ways)? VA10 is high when VIC accesses reverse chars from the character ROM. I have good continuity between those three pins on the respective ch...

Do you have an effective means to transfer files between VIC-20 and PC? Do SAVEs work (i.e. can you reload saved programs)? If so, please run the following program ( download ) with LOAD"...",8 and RUN on your suspect VIC-20 and attach the 3 resulting files in a *.zip archive here. Are yo...

Does the VIC react to any keyboard input? If so, how fast is the repeat rate if you press and hold the space bar? Do you own a multimeter and know how to use it? Yes, I can type on the keyboard fine. If I hold down the space bar, it takes about 3 seconds for the cursor to go from left side of scree...

I have a VIC-20 board revision 324003 that starts up, but the cursor blinks too fast. I have a second 324003 board missing VIC chip and CPU. I put the VIC chip and CPU from the board that blinks too fast into the one missing chips, and the cursor blinks at normal rate. So doesn't seem to be CPU or V...

I noticed in one of Adrian Black's videos, he uses a bench power supply to supply 5V @ 1.1A to his older VIC-20 with 2-prong power supply. In video he indicated the only thing that wouldn't work is 9VAC for the cassette motor: https://www.youtube.com/watch?v=BGnNlVzUCZM&t=528s I have a VIC-20 wi...