Strange writing on vic 20

[mrmoonlight]

Hi can any one help with my writing problem on the vic 20 when I boot up it works very well apart from the strange markings on the writing ,is there away of improving this please, best wishes Brian

[FD22]

At power-on, try:

Code: Select all

POKE 7680,0:PRINTPEEK(7680)
POKE 7680,255:PRINTPEEK(7680)

That pattern looks suspiciously like a bad RAM chip - if you get something other than zero back from the first PEEK, and/or something other than 255 from the second, that's what it is.

[GreyGhost]

I doubt that will show you anything. It doesn't look like the screen memory is being effected. It looks more like the character ROM is corrupted. I'd try a program that uses redefined characters and see what you get, but not one that gets it's data from the character ROM. Try re-seating it.

[Witzo]

It does remind me of the problem with flaky character ROM in this video:

http://www.youtube.com/watch?v=L_OXZBR66-8

[mrmoonlight]

I doubt that will show you anything. It doesn't look like the screen memory is being effected. It looks more like the character ROM is corrupted. I'd try a program that uses redefined characters and see what you get, but not one that gets it's data from the character ROM. Try re-seating it.

Hi being a little new to the vic may I ask which of the chips should I try to reseat as I am not sure what to look for best wishes Brian.

[GreyGhost]

I don't know off hand which chip is the character ROM. Someone else on here may be able to help locate it, but I'd say if it's in a socket, reseat them all. Doesn't take much. Move them around slightly with your finger. Press them down gently. Worse case you may have to pull them and reseat them keeping in mind their orientation. Pulling them is best done with an IC puller, but I have done it with a flat blade screw driver of knife. Doing it this way may bend the pins so be very careful if you remove them completely. Slow and steady. Try to load and run a program that uses redefined characters first.

Hope this helps.

[ral-clan]

I doubt that will show you anything. It doesn't look like the screen memory is being effected. It looks more like the character ROM is corrupted. I'd try a program that uses redefined characters and see what you get, but not one that gets it's data from the character ROM. Try re-seating it.

Hi being a little new to the vic may I ask which of the chips should I try to r-eseat as I am not sure what to look for best wishes Brian.

I can't find a picture right now, but just open the VIC-20 and press down all the socketed chips. There's only about a half-dozen, and it's good practice to do it on all chips anyway.

You could also slightly unseat them with a screwdriver then press down.

Just make sure and touch something metal in your house, like a metal air vent or the screw in the centre of the plate of a power outlet socket in order to ground yourself of static electricity first - or wear an anti-static wristband.