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NOT WORKING CBM 3032

daver2 said:
La resistenza è di soli 27 Ohm. Smetti di usare la funzione 'beep' del tuo multimetro!

Utilizzare un'impostazione a bassa resistenza o semplicemente seguire la traccia PCB dal pin 12 G7 al resistore. È l'altra estremità che vuoi!

Dave
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Ok thanks so much sir!
 
Are these jumpers corrects?
 

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Desperado said:
Dave i swapped the two resistor s' lead but i have same situation :(
Click to expand...

I want you to post a video of the PETTESTER screens after you perform a reset please so I can see what the state is for myself. Can we also wait for the countdown to reach zero and the start of the full memory test on the video also.

Dave
 
daver2 said:
I want you to post a video of the PETTESTER screens after you perform a reset please so I can see what the state is for myself. Can we also wait for the countdown to reach zero and the start of the full memory test on the video also.

Dave
Click to expand...
unfortunately, while I was fixing the legs of the resistors, one broke right at the edge of the resistor.. Since I don't have spare parts with this value, I ordered new resistors on Amazon... they will arrive tomorrow!
 
Thanks, that video was very informative.

So, the problem lies somewhere in the VDU circuitry. I could see some changes in the displayed characters on the screen that cannot be as a result of faulty main RAM or the CPU.

So, can you remind me, what chips are socketted in the VDU section? In particular, are both video RAM devices now in a socket?

Dave
 
daver2 said:
Thanks, that video was very informative.

So, the problem lies somewhere in the VDU circuitry. I could see some changes in the displayed characters on the screen that cannot be as a result of faulty main RAM or the CPU.

So, can you remind me, what chips are socketted in the VDU section? In particular, are both video RAM devices now in a socket?

Dave
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Thanks Dave!
Only one Ram video is on socket...UF7...also the ls244 on UE7 is on socket!
Can i resold the two resistors in original place now?
 
>>> Only one Ram video is on socket...UF7...also the ls244 on UE7 is on socket!

I think it would be sensible to socket the other video RAM I am afraid.

This way we should be able to remove the video RAM and use eight 100 Ohm (or so) resistors to 'force' characters to fill the whole screen. This should test out the video data latch, character generator and the parallel to serial shift register.

If that turns out OK, we will have to look at the video address multiplexers, and video data bus buffers next.

Dave
 
Dave great news!
I inserted a socket and i replaced the other video ram, all trash characters are gone, the pettester was stuck on dram test though. I then checked the jumpers and saw that jumper "C" in the photo was open instead of closed. I soldered the jumper and now the dram test started too! Can i try to remove pettester and can i insert original rom?
 

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I am desperate!!!
I inserted original ue8 rom but i have random chars screen :( Maybe bad rom?
 
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