First of all, what's a 2001 B? Not a 2001-8 by any chance?I recently aquired a Pet 2001 B and when I power it up all I get is garbled letters all over the screen! Does anyone know what might be causing this?? Would really like to get it goin any help would be great!
Hmm, nasty. It's quite likely that one of those chips is bad but, being non-standard, they're going to be hard to test even if you had the right equipment. Not only that, but it's going to be a problem finding replacements if you need them.yes its a 2001 8 . the numbers are 6540 and 6550. Ive reseated all the chips and still same result just random characters all over the screen. It doesnt have a built in cassete player. Im located in regina saskatchewan canada. Im very novice at all this but like my commodores so trying to learn all I can. Thanks for any info.
Pretty well all 2001s had RAMs & ROMs in sockets; makes it convenient, but also a common source of trouble because they were pretty crappy.Most common cause of garbled random letters on old machines is bad RAM. Unfortunately I believe the RAM is soldered down to the board so it's not exactly easy to test for. Commodore never were much of ones for socketing components that were actually prone to dying -- they just socket all the stable stuff.
Hell, most PET 2001's used Ceramic ram's... check them over, see if any have visible cracking. (switching to plastic wasn't just about cost)
You can sure make something simple look complicated and hard to read... ;-)The chip numbers are as in order from left to right sitting in front of the computer
02 4 2181 023 5180 HN462532G(which apears to be a replacement chip on an adapter board of some sort also has 1982 SEW B2/3 $FIX on it) 0220680A 021 3280A
020 3980A then at the back right of the board one more 6540 0101978A
Did you try the adapter in slot 7 instead of 4?Ok I rearanged the chips this morn and yes slot 7 is empty. Nothing has changed but at least these are in order now..thanks.
I also noticed this morning that when i wiggle the wires going up to the monitor the screen can go blank..wondering if maybe the problems up there with that area ??? Would I be able to replace the roms or reprogram??
Where are all the other PET experts? No other suggestions?
I'm sure that when I first saw it there was an assembled version available for sale that used a '512 EPROM, and I think someone in fact just installed one but I can't recall who or where, but all I can find now at a quick look is a flash version and it's not clear whether assembled versions are still available:Does anyone have the link to the person that sells the total ROM replacement unit?
As a matter of fact Jim Brain sells an adapter that lets you replace a 6540 with a 27xx chip with jumper options to select a bank out of up to 512KB. I used one to put a 2764 into the character generator socket to permit selecting alternate character sets, and another one contains a 27256 which holds both BASIC 1 and the upgrade BASIC switch-selectable; that does involve a half-dozen or so connections to the MB however.I have the link to the person that sells a 6540 adapter including the replacement 2716 (see below). The price is probably way too costly if all 7 chips are needed.
No problem; if it turns out that one or more ROMs are bad I might have a 6540 replacement anyway; if not I can put a 27xx in one of JB's adapters.Maybe Andrew should take you up the the kind offer to test the ROMs and just order the one he may need.
Ah, OK. I thought I'd just recently read on one of the PET forums that someone had installed one, and thought it might have been you. Do you remember a version that used a 27512 instead of flash RAM, or am I dreaming that?Sorry, I have never used either of Nicolas' various boards. I've only read about them and met him in person.
As a matter of fact Jim Brain sells an adapter that lets you replace a 6540 with a 27xx chip with jumper options to select a bank out of up to 512KB.
http://www.jbrain.net/products/ROM%2del-6540.html
Ah, OK. I thought I'd just recently read on one of the PET forums that someone had installed one
Amen! (Are ya reading this, Jim? ;-)Mike,
Thanks for the Jim Brain information. I tried to find it previously but could never get to the page with the board info. He should work on making his website easier to navigate.
-Dave
One other thing to check in the meantime is page 0 RAM; try swapping ICs I1 and J1 with a pair from elsewhere, e.g. I8 and J8.I would like to take you up on the offer to test the ROMs. Its likly where the problem seems to be. Id need your address and I'll get them in the mail.
I had a reply from Nicolas: he did indeed sell assembled units at one time but these days he doesn't have the time; he does however have the PCBs, GALs and flash chips and I'm thinking of ordering a couple of sets and resell them at cost in assembled form in case someone without soldering skills needs one. We'll see...Does anyone have the link to the person that sells the total ROM replacement unit?
I have a couple of Jim's version of this and could supply a single ROM replacement if necessary.I have the link to the person that sells a 6540 adapter including the replacement 2716 (see below). The price is probably way too costly if all 7 chips are needed.