Pet 2001 repair

[polishedball]

I bet you guys didn't see that coming

Anyhow on power up this is what I get, anyone scene something like this before?

The board revision uses 2114 memory if that tells anything?
this is a quick pic of the board, resized

 

[MikeS]

I bet you guys didn't see that coming

Anyhow on power up this is what I get, anyone scene something like this before?

The board revision uses 2114 memory if that tells anything?

Tells us that if you need one you'll have a much better chance of finding one than the 6550s. If you're really lucky those ROMS are 2332s instead of 6540s; what are the numbers on the ROMs?

this is a quick pic of the board, resized

Much better! Thanks -)

Usual story: Check sockets, bad ROM most likely, bad RAM next likely, after that anything goes. What happens if you remove the socketed 2114s?

 

[polishedball]

Thanks will be cleaning up the board and taking a close look, some numbers are missing or very faint and can;t see without going to the bench. The one I can read easily is a motorola chip part 901447-,-02,-07. Can you tell the type from that?

Also if it is the 2332 type is there a pin for pin replacement? available? I was thinking the TMS2532 could be used as a straight replacement is that correct?

 

[polishedball]

Tells us that if you need one you'll have a much better chance of finding one than the 6550s. If you're really lucky those ROMS are 2332s instead of 6540s; what are the numbers on the ROMs?

Are these roms 2332's or 2316's in which case I could use 2716's part numbers are H1 901447-09
H2 901447-03 H3 901447-05 H4 901447-06 H5 901447-02 H6 901447-04 H7 901447-07

Sorry for all my chaos with roms, I just want to get replacements coming to burn.

 

[dabone]

Is it the same pattern each time? Have you verified that you are getting +5 out of all the 7805 regulators? I had a garbage screen on mine until I replaced the first (closest to the front of the case) one.


Later,
dabone

 

[polishedball]

Is it the same pattern each time? Have you verified that you are getting +5 out of all the 7805 regulators? I had a garbage screen on mine until I replaced the first (closest to the front of the case) one.


Later,
dabone

Same screen each time, all regulators are good.

Thanks for the idea.

 

[MikeS]

Are these roms 2332's or 2316's in which case I could use 2716's part numbers are H1 901447-09
H2 901447-03 H3 901447-05 H4 901447-06 H5 901447-02 H6 901447-04 H7 901447-07

Sorry for all my chaos with roms, I just want to get replacements coming to burn.

2316s, so 2716s should work.

Looks like BASIC1 with revised C000 ROM; if you've got the EPROMs and a burner you could upgrade at the same time...

Of course if you've got a burner presumably you can read the ROMs and check them; for that matter you could presumably also read them in one of your other PETs.

 

[polishedball]

2316s, so 2716s should work.

Looks like BASIC1 with revised C000 ROM; if you've got the EPROMs and a burner you could upgrade at the same time...

Of course if you've got a burner presumably you can read the ROMs and check them; for that matter you could presumably also read them in one of your other PETs.

Great idea, i'll read them and compare checksums with the known bin files.

 

[polishedball]

2316s, so 2716s should work.

Looks like BASIC1 with revised C000 ROM; if you've got the EPROMs and a burner you could upgrade at the same time...

Of course if you've got a burner presumably you can read the ROMs and check them; for that matter you could presumably also read them in one of your other PETs.

Well I must say I have scene corrupt data on roms before but 7 of the 8 including the character rom tested blank, one had matching code. Glad it did or I would have thought my reader/burner had failed. Is that how eproms fail the code just disappears, never scene it before.

If these test blank and are effectively erased can I write back to them?> Obviously i'll be ordering all new but am curious.

Thanks

 

[carlsson]

You could try to erase and program them, then wait a week and see if something still is there. At least one of the 2532 chips I sent to Italy and France turned out to be "blank" when I got them in return a few weeks later. It might have been a bad programming or something that zapped the chip once inside the computer, but also old chips no longer usable.

 

[MikeS]

Well I must say I have scene corrupt data on roms before but 7 of the 8 including the character rom tested blank, one had matching code. Glad it did or I would have thought my reader/burner had failed. Is that how eproms fail the code just disappears, never scene it before.

If these test blank and are effectively erased can I write back to them?> Obviously i'll be ordering all new but am curious.

Thanks

Umm, unless I missed something we're talking about the original ROMs here, not EPROMs?

Unlike EPROMs/EEPROMs/Flash etc., ROMs are permanantly programmed and can't be reprogrammed or erased (although of course they can be damaged and appear blank).

But I'd double-check; it seems very unlikely that 7 out of 8 ROMs would fail, and I don't see how you could get characters on screen with a blank character generator... ;-) Sumpin' doan soun rite...

Did you try putting them into one of the spare sockets in one of your later PETs and using the MLM or peeking from BASIC to see what they say?

 

[polishedball]

Umm, unless I missed something we're talking about the original ROMs here, not EPROMs?

Unlike EPROMs/EEPROMs/Flash etc., ROMs are permanantly programmed and can't be reprogrammed or erased (although of course they can be damaged and appear blank).

But I'd double-check; it seems very unlikely that 7 out of 8 ROMs would fail, and I don't see how you could get characters on screen with a blank character generator... ;-) Sumpin' doan soun rite...

Did you try putting them into one of the spare sockets in one of your later PETs and using the MLM or peeking from BASIC to see what they say?

Yes you are correct they are factory roms, seemed very strange but I double checked everything and the one that read correct with matching checksum i even did between the others over to make sure everything was reading right.

I'll check em out in a spare slot in my working machine.

 

[MikeS]

Yes you are correct they are factory roms, seemed very strange but I double checked everything and the one that read correct with matching checksum i even did between the others over to make sure everything was reading right.

I'll check em out in a spare slot in my working machine.

Well, I think you said that the CG ROM is one of the blank ones so I'd expect random garbage on screen (if anything) instead of actual characters. BTW, when you say "blank" do you mean all 0's or all F's? A blank EPROM would contain all F's, which might suggest that the chip is not being selected (wrong type selected?); does your programmer/reader say the same thing whether a chip is inserted or not?

 

[dave_m]

Well, I think you said that the CG ROM is one of the blank ones so I'd expect random garbage on screen (if anything) instead of actual characters.

Mike,
That sounds right, the character generator ROM must not be totally blank if some valid raster scan characters are being seen on the screen.

We may have to call you the"Sherlock Holmes of the PET" from now on. For short, maybe we'll just call you "The PET Detective".
-Dave

 

[polishedball]

Well, I think you said that the CG ROM is one of the blank ones so I'd expect random garbage on screen (if anything) instead of actual characters. BTW, when you say "blank" do you mean all 0's or all F's? A blank EPROM would contain all F's, which might suggest that the chip is not being selected (wrong type selected?); does your programmer/reader say the same thing whether a chip is inserted or not?

I just did a blank check on the chip when they all reported the same checksum after a read. I'll try cleaning the leads as well since they are tarnished pretty bad, maybe the zif socket on the programmer isn;t getting good contact. WIll let you know results of that or peeking into them in another pet later. Thanks everyone.