Hi guys,
I'm trying to repair a beautiful 32k 4032 and have a really really strange problem. I have a "spare 4032" which I used to check some parts (by exchanging them with the working 4032), so I can say that
* All ROMs are ok
* Both 6520 are ok
* 6522 is ok
* 6502 is ok
* CPU CLK is ok (checked with an scope)
Symptoms:
* After power up screen is garbled and turns black after a couple of seconds
* I changed 4x 4116 RAMs until now (sockets J2, I2, J3, I3)
* Before changing the 4x 4116 the screen sometimes showed "counting characters" or single, static characters instead of the black screen
But now comes the spooky part:
When I see the black screen and I switch the PET off, I sometimes see the start screen characters (### Commodore Basic ....###) for a glimpse of a second on the screen before it vanishes.
What could cause this kind of symptoms? Does switching off the machine "release" a kind of IRQ? Strange ...
Any ideas?
Kind regards,
Ingo
I'm trying to repair a beautiful 32k 4032 and have a really really strange problem. I have a "spare 4032" which I used to check some parts (by exchanging them with the working 4032), so I can say that
* All ROMs are ok
* Both 6520 are ok
* 6522 is ok
* 6502 is ok
* CPU CLK is ok (checked with an scope)
Symptoms:
* After power up screen is garbled and turns black after a couple of seconds
* I changed 4x 4116 RAMs until now (sockets J2, I2, J3, I3)
* Before changing the 4x 4116 the screen sometimes showed "counting characters" or single, static characters instead of the black screen
But now comes the spooky part:
When I see the black screen and I switch the PET off, I sometimes see the start screen characters (### Commodore Basic ....###) for a glimpse of a second on the screen before it vanishes.
What could cause this kind of symptoms? Does switching off the machine "release" a kind of IRQ? Strange ...
Any ideas?
Kind regards,
Ingo