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Color Classic Video AB issues

Big Ben

Well-known member
Hello there,

I'm currently trying to finish the repair of my Color Classic but it kinda went wrong.

Quite some time ago I did a full recap of all the logic and analog board, with deep cleaning. After calibrating all the video part it was working well.
But all that calibration was done while beeing at an event and when a came back home my CC didn't survived the travel. :cry:

Here the few thing that went wrong:
  • Missing green signal
  • Hissing/"crispy" noise when plugged and power switch turn on (noise stay the same if the computer is booted) - only for few minutes, disappear when AB is warmed up
  • Constrast is higher than expected
  • Video crunched and deformed (see picture, dotted yellow rectangle represents the actual video size when everything is ok)
  • Sometimes video goes off for fraction of time with a "tick" sound (kinda like a defective flyback on a iMac) - mostly when the computer is not warmed up
After a while digging into the problem the video snapped back to a normal state. Proper height, no distorsion and then failed again few minutes later.

I did manage to find out why the green signal was missing, it's a bad contact between the analog board and the CRT's neck board in the RGB signal cable. It will be a pain to fix since the connector is glued but doable.

I don't know where to start.
Capacitors have been properly replaced, I double checked.

I suspect something needs to be replaced or adjusted like the CRT is not properly driven.

Unrelated but 12V and 5V are fine and stable.

Any ideas?
 

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techknight

Well-known member
Resolder the bad solder joints in the various spots on the analog board. This is a known issue on analog boards.

Also, make sure you clean the adjustment pots with DeOxit F5. Everything should be good from that point.
 

Big Ben

Well-known member
Thanks for the advice, I totally forgot that point.
I thought I did some resoldering but I actually didn’t.

So I just did some of them. It’s not noisy anymore!
I also found the problem with the green signal, the wire wasn’t properly connected to the corresponding pin.

Screen is still deformed and a bit flicky, so I think I need to track some bad solders.

I don’t have any DeOxit F5 but I might something similar, just need to check if it will work on potentiometers.
As far as I observed it seems they work properly but a bit of cleaning won’t hurt
 

Big Ben

Well-known member
Little update: did some resoldering, now working fine even when cold.

I guess it’s another saved color classic! 😀
 
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