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CBM PET 3032 STRANGE BOOT

maybe I found the problem...it's a white socket from a rom...I sprayed a little spray and now it's gone again...I have to try to replace it!
 
Another Pettester fault!
 

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I am desperate! i tried piggy on every lower bank ics but i have always same error...also when it warms up, the pettester gets stuck on the first screen...
 
Have you bought yourself any freezer spray?

Something sounds temperature sensitive. It may not be the RAM of course.

Dave
 
daver2 said:
Have you bought yourself any freezer spray?

Something sounds temperature sensitive. It may not be the RAM of course.

Dave
Click to expand...
Yes, i used this freeze spray on every ic but the pet remains blocked :(
 
If you get inconsistent results with the RAM - then it could be the RAM data bus buffers OR it could be the dynamic RAM REFRESH circuitry. Gary found an interesting fault on his dynamic RAM refresh logic.

Dave
 
For the refresh signals scope the signals named RA1 through RA6 to be found on the pins of E3 through E6.

Look for TTL signals (a good HIGH and LOW signal level) and report the frequency you measure.

Dave
 
daver2 said:
For the refresh signals scope the signals named RA1 through RA6 to be found on the pins of E3 through E6.

Look for TTL signals (a good HIGH and LOW signal level) and report the frequency you measure.

Dave
Click to expand...
Thanks, but when PET is stucked or not?
 
E3:
PIN 5-6: 7,8 KHz

E4:
PIN 5-6: 250 KHz

E5:
PIN 5-6: 62,5 KHz

E6:
PIN 5-6: 15,6 KHz

Same result with PET stucked :(
 
You should have six (6) readings. Why only four?

It doesn't matter about the state of the machine. The frequencies and voltage levels should be constant and independent of the state of the machine.

Dave
 
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