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Commodore PET 2001-8 stuck on garbled screen

Very good! That was a hard one because it really only affected WRITEs and a NOPPer only does READs.

So... now... put the Tynemouth board to one side... put a CPU in the CPU socket... put the H7 PETTESTER in H7 and put H1..H6 back in their sockets.

Make sure you have some RAM installed; it can be 6550 or the 8k Replacement whatevs.

So what do you see...

PS
We have a few more things to do yet but it's looking pretty damm good to me!

PPS
We also need to make sure onboard RAM works... PETTESTER will be good for testing that.
 
With the first two banks of ram filled. If that's ok for these tests.
Pic allso of what's installed.
 

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Good Stuff.

Now @daver2 He currently has PETTESTER the F8 variant in H7... so that will mess up the F checksum... if we ignore F...

(I attach an image of it for the LOLs... )

To be honest none of those checksums look great!

@RGM Can you take a photo of the ROMs showing their markings in-situ please.... all H1...H7 need to be populated. (H7 will be the tester; leave the original H7 901349-07 to one side for now)

@RGM did you say you had the technology to read them?

PS
I'll mostly leave you in @daver2's hands to work through a few things for a bit

PPS
By my calculation if 901439-04 was installed in H4 and my version of your tester PETTEST2KF04 were in H7 that should give a F checksum of CF83
 

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Let's concentrate on the ROMs first shall we...

What ROMs have you got fitted to the machine, in which sockets and what part numbers are on the ROMs.

We should see consistent checksums (they don't vary as the tests run) and they should match those in my documentation.

Dave
 
Nivag Swerdna said:
Good Stuff.

Now @daver2 He currently has PETTESTER the F8 variant in H7... so that will mess up the F checksum... if we ignore F...

(I attach an image of it for the LOLs... )

To be honest non of those checksums look great! @RGM did you say you had the technology to read them?

PS
I'll mostly leave you in @daver2's hands to work through a few things for a bit
Click to expand...
Yer I have a willem eprom reader. I have only briefly tried it. Would be nice to compare my roms with some images.

I have filled up the rest of the banks of memory with 6550s. First four are subs All condition unknown. More testing has happened from Dave's pet tester.

Btw, Internal tape drive is working better in that the motor does not constantly run under basic and it now says searching when I press play. But still not loading.
 

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You really need to take those RAMs out...

Can you get it back to the state it was before please (post #282).

Dave
 
RetroGadgetMan said:
Yer I have a willem eprom reader. I have only briefly tried it. Would be nice to compare my roms with some images.

I have filled up the rest of the banks of memory with 6550s. First four are subs All condition unknown. More testing has happened from Dave's pet tester.

Btw, Internal tape drive is working better in that the motor does not constantly run under basic and it now says searching when I press play. But still not loading.
Click to expand...
I updated the post above; let's work on RAM and ROM.... TBH... please read my revised post #283 and follow the instructions. As for RAM I think you need very little... J1 and I1 and possibly J2 and I2 would be enough for now. Also... I don't think we are 100% confident in those substitute RAMs... so use 6550s.
 
daver2 said:
Let's concentrate on the ROMs first shall we...

What ROMs have you got fitted to the machine, in which sockets and what part numbers are on the ROMs.

We should see consistent checksums (they don't vary as the tests run) and they should match those in my documentation.

Dave
Click to expand...
Just completed a test ref Nivags suggestions post #281 H1 and h6 and your pet tester. Unable to read the ceramic one H1 And the first three digits are unreadable on H6 other number is 0678a. Pics attached.
 

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RetroGadgetMan said:
Just completed a test ref Nivags suggestions post #281 H1 and h6 and your pet tester. Unable to read the ceramic one H1 And the first three digits are unreadable on H6 other number is 0678a. Pics attached.
Click to expand...
I mean H1 and H2 and H3 and H4 and H5 and H6 and H7 (PETTESTER)!

And take a photo of the screen!
 
Nivag Swerdna said:
I updated the post above; let's work on RAM and ROM.... TBH... please read my revised post #283 and follow the instructions. As for RAM I think you need very little... J1 and I1 and possibly J2 and I2 would be enough for now. Also... I don't think we are 100% confident in those substitute RAMs... so use 6550s.
Click to expand...
Btw Substitute rams have been tested as video ram and all worked since we replaced G4
 
I think you have both some very dead ROMs and very dead RAMs as well!

The "random screen of death" indicates that one (or more) of the ROMs is preventing the PETTESTER ROM from running correctly.

Dave
 
@daver2 I believe the ROMs are also not in their correct locations? I cannot read most labels but I would expect a -013 to live in H2 not H6? A -016 does look correct in H4.

I always found the numbering very confusing.

I believe it would be 901439-01, 901439-02, 901439-03, 901439-04, 901439-05, 901439-06, 901439-07 for the very original Basic1... reading H1 to H7... right to left... but the actual markings are 6540-011, 6540-013, 6540-015, 6540-016, 6540-012, 6540-014, and 6540-018

H1 is replaced by 901439-09 with marking 6540-019 in what I call Basic 2.

PS
When I bought my PET it didn't work and had the ROMs in random locations... I think that was the prior owners attempt to fix it... put the ROMs in random orders!
 
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Ok I had them in back to front🙄🤪 I just looked at the pic from when I bought it for the corect orientation. I have pulled one at a time from h6 downwards and it's now booting the test with H4 removed. See pics.
 

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CA92 is the correct checksum for rom-1-e000.901439-03.bin which is currently in H3!
Mark it as H3 and take it out and put it aside... move another ROM into H3 and repeat the test
 
The way that variant of PETTESTER works is that it creates a checksum for the E socket (which is H3) on the basis of the single device there... you can cycle your ROMs through there to get individual 2K checksums...

Code: 
rom-1-c000.901439-01.bin 0xe85f
rom-1-c800.901439-05.bin 0xe4fe
rom-1-d000.901439-02.bin 0x31fc
rom-1-d800.901439-06.bin 0x1e49
rom-1-e000.901439-03.bin 0xca92
rom-1-f000.901439-04.bin 0xf21c
rom-1-f800.901439-07.bin 0x1a88
rom-2-c000.901439-09.bin 0xe7cb
rom-3-c000.901439-13.bin 0xa347
rom-3-c800.901439-14.bin 0x94f1
rom-3-d000.901439-15.bin 0xa7f1
rom-3-d800.901439-16.bin 0xa879
rom-3-e000.901439-17.bin 0xfdbf
rom-3-f000.901439-18.bin 0x2263
rom-3-f800.901439-19.bin 0x5a35

Do this with each ROM you have and try and identify if they match one of them... label as you go... add a sticker and at least write the checksum on them!

Looks like you have a working rom-1-e000.901439-03.bin at least. (It has a CA92 checksum; shown as E=CA92)

For the other checksums it works in pairs... e.g. H1 & H5 combine to be the C checksum... once you have worked out which ones work and where they go we can try and get some pair checksums to work too; ignore the pairs for now.
 
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RetroGadgetMan said:
Ok I had them in back to front🙄🤪 I just looked at the pic from when I bought it for the corect orientation. I have pulled one at a time from h6 downwards and it's now booting the test with H4 removed. See pics.
Click to expand...
When you say back to front, you mean in the wrong orientation in the socket ? (or did you mean that you simply mixed two up) If that did happen, reversed in the socket, it reverses the applied power polarity to the ROM, this will most often damage the ROM. If that happens to a ROM it would likely render it either A) damaged or B) untrustworthy in the future. So it might pay to create replacement ROMs for any that this event has happened to, even if they still appear to be working.
 
Hugo Holden said:
When you say back to front, you mean in the wrong orientation in the socket ? (or did you mean that you simply mixed two up) If that did happen, reversed in the socket, it reverses the applied power polarity to the ROM, this will most often damage the ROM. If that happens to a ROM it would likely render it either A) damaged or B) untrustworthy in the future. So it might pay to create replacement ROMs for any that this event has happened to, even if they still appear to be working.
Click to expand...
I had the roms mixed. I started from left to right ,H1 in H7. I confused myself when I marked them 1+7 with a pencil from left to right whe I first got the pet.
I hope some of them can be salvaged. One apears to be functional and one not so far but that could change.
 
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