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Cbm 2001 Pet strange boot

Good evening guys....i am desperate, i putter Nivag magic_rom on Ud9 socket but when i turn on i have only scrambled chars screen :(
I have original edit rom on ud8....
 
This is screen with magicrom on Ud9 and without any roms (only chars rom on board).
 

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This is a test ROM.

Until Nivag tells us what the ROM is supposed to do, how do we know what it is displaying?

Ah, we cross posted!

Dave
 
Ok...the only Pettester that worked it was the first posted by Nivag (4k on Ud9).....
The original pettester rom (2k on ud8) stay stuck on first page...
This magic_rom doesn't works :(
 
Until Nivag tells us what the ROM is supposed to do, how do we know what it is displaying?

I'm trying to keep that part a mystery to avoid any doubt when it does run.

So @Dave_C78 what happens if the UD9.bin is put in UD9... does that show scrambled too now?

Maybe the buffers are replaced with more bad buffers?
 
OK so all PETTESTERs now behave the same?

Can you remove both PIAs and the VIA and try again see if anything changes?
Yes....
I already remove the two 6520 and 6522 but nothing changes...
I tryied also other new 244 ics without success...
 
An observation. This fault is playing hide and seek with us - so we have to use cunning to flush it out.

So, let’s call this “configuration A” shall we? We know that this configuration ‘sticks’ at the PETTESTER video screen RAM test. Mark the EPROM “config A”.

Get a pen and a notebook and write down the EXACT configuration of the PET (e.g. what chips are in and out). If we change the configuration in the future, you need to write down exactly what you changed.

My question is “what is the difference between this configuration and what you had when you took the photographs back in posts #343 and #368?”.

If you have the same configuration, then the fault is intermittent - and hence coming and going.

Dave
 
An observation. This fault is playing hide and seek with us - so we have to use cunning to flush it out.

So, let’s call this “configuration A” shall we? We know that this configuration ‘sticks’ at the PETTESTER video screen RAM test. Mark the EPROM “config A”.

Get a pen and a notebook and write down the EXACT configuration of the PET (e.g. what chips are in and out). If we change the configuration in the future, you need to write down exactly what you changed.

My question is “what is the difference between this configuration and what you had when you took the photographs back in posts #343 and #368?”.

If you have the same configuration, then the fault is intermittent - and hence coming and going.

Dave
unfortunately too many changes have been made ... now I don't remember what configuration I had and what kind of pettester I had entered :(
I am desperate now
 
So now i have this:

CONFIGURATION A:

PETTESTER UD9 POSTED BY NIVAG

ALL ORIGINAL ROMS INSERTED ON BOARD
 
I thought you said that the 6520 and 6522 devices are removed?

These are part of configuration A.

>>> unfortunately too many changes have been made ... now I don't remember what configuration I had and what kind of pettester I had entered.

This is why you need to get into the habit of writing down what you do and what you observe in a notebook. It is what I do and it helps me to understand what I have done and what I obtained. In theory then I can return to a previous configuration and observe that I get the same result(s).

Once I think I have found a solution to a problem, I can then go back in the notebook and identify if the solution would account for all of the anomalous things I saw or not - and (if there is any doubt) I can repeat the previous test configurations to see if the problem really has gone away.

I am renowned (both at Church and work) to be incredibly diligent about documenting the things that are done and evidence collection. There are usually some questions occurring in the future (maybe months after our work) that I can go back to and dig out the answers...

For simple (and easy-to-fix) issues this is not a great deal; but for a machine with many (or intricate) faults - it is a must.

Dave
 
I am renowned (both at Church and work) to be incredibly diligent about documenting the things that are done and evidence collection. There are usually some questions occurring in the future (maybe months after our work) that I can go back to and dig out the answers...
Holy truth!! I will learn to do this too!
I thought you said that the 6520 and 6522 devices are removed?
i removed these ic only for a test but after i re inserted on board!
 
i removed these ic only for a test but after i re inserted on board!

Yes but you still need to document the fact that the fault condition doesn't change whether they're fitted or not. Could be relevant further down the line. Stop despairing and be methodical. You'll get there in the end.

Alan
 
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