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After changing the 6520 it's now working :) @Hugo Holden Thanx for this info. I will try to contact them. I need a 6520 :)

i will desolder the 6520 tomorrow and try a spare one. Solder first a socket.

That's correct

I tried a few pokes poke 0 give 191 as output

If i use this --> POKE 59426,255 and then PRINT PEEK(59424) I get as return 90 and see no change on 6520 output

Is soldered in. :(

for example: 10 POKE 59427, 60:REM SETS DAV HIGH 20 POKE 59427, 52.REM SETS DAV LOW 30 POKE 59427, 60:REM SETS DAV HIG I don't see any changes with scope on de DAV output (Pin 19)

That's also a possiblity, but i don't expect that. The 6520 is not responding to the poke's. Or i am doing it wrong..

Can you tell me on what chapter / page it is in the book? IEEE488

This is the output. I think 6520?

Well, you mentioned the title, and now i know i have the real book. ;)

Do you also know how the check if the 6520 is working ok? IEEE488 port is not working.

The monitor is also working now. R752 and R753 was defect. (56 Ohm)

I know ;) I have worked at a repair department for Television back in the nineties. Repaires a lot of TV's.

Now i need to focus on the monitor. There is no contrast at all.

Yes it is :)

piggy-back did the trick ;) I found that UA17 was defect. Replaced it and now it's working.

Here is de screendump when it was working:

Do you mean it performed the DRAM test for 2 hours and increased the PASS counter on a regular basis? <-- Yes! Or you have just had another fault occur by powering OFF and back on. I think that this is the case. because a had other failure before. First i had this screen. Then i replaced UC5...

There was some kind of sortcut on UA7. After i fixed that, i was getting the normal CBM screen. Then is used the pettester to see everything was ok. It run correct for like 2 hours. Then i placed the rom back and it was not working anymore. So placed the Pettester back and was getting the...