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rjsquirrel
July 8th, 2005, 02:26 PM
I decided to try and revive my Commodore PET 2001 that has been in the basement for many years (I'm the original owner). When I turn it on, the screen is filled with seemingly random alpha-numeric and graphic characters. They are static, but vary somewhat in configuration if I cycle the Power. Does anybody have any suggestions? Thanks.

Rick Ethridge
July 8th, 2005, 05:58 PM
Sounds like bad memory. Try reseating the chips first and check again.

Donni
July 8th, 2005, 11:11 PM
There are a few versions of the pet2001.
If you have the PET2001-8c version with the 6550 ram ic's, it's a good guess that one or more of them are defective.
You can find out by simply swapping the two video rams, with two of the 16 memory rams.
That way you will get a picture, but obvious the memorycount won't be correct.
A defective ROM is also very likely.
It's also a good idea to pull all of the ic's out of there sockets and push them back in again a couple of times.

rjsquirrel
July 9th, 2005, 05:03 AM
Thanks to both of you for the suggestions. I tried reseating the socketed chips, but no change. I also tried swapping the Video RAM with other RAMs, but also no change. I've checked all power supply voltages and they are correct. Any other thoughts?

Donni
July 9th, 2005, 04:17 PM
Any other thoughts?

Next best guess would be the one or more defective rom's.
But just like the 6550 ram ic's these are hard to get.
I designed a replacement board for it some time ago.

http://members.lycos.nl/ijmtu/hpbimg/pet2001rom_ram_Rep.jpg

I think something similar is sold on some German site which I can't remember right now.

Donni
July 9th, 2005, 04:25 PM
Found it:
http://x1541.de/

vbriel
July 13th, 2005, 03:30 PM
Donni,

I have a 2001-8 I'd like to get going. I got it to power up but I get different characters for the keys I press. It appears to bring up the BASIC message at the top of the screen but in the wrong characters. Any ideas?

Thanks,

Vince

Donni
July 19th, 2005, 09:12 AM
Donni,

I have a 2001-8 I'd like to get going. I got it to power up but I get different characters for the keys I press. It appears to bring up the BASIC message at the top of the screen but in the wrong characters. Any ideas?

Thanks,

Vince

Sorry, never seen that before.
MAYBE the character rom ??

carlsson
July 23rd, 2005, 05:03 AM
Can it have something to do with the power regulator? Someone with a faulty VIC-20 that randomly displays wrong and correct characters was suggested to look at the power regulator, but I don't know more.

http://www.themotionstore.com/leeedavison/6502/vic20/psufix/index.html

You may want to post to newsgroup comp.sys.cbm, search the Internet or even join the cbm-hackers mailing list which is a hardware-centered list full of skilled people.

vbriel
July 23rd, 2005, 05:37 AM
Yeah, I posted to the newsgroup, it is video ram, maybe all of the ram has bad bits causing the wrong characters to display on the screen.