A1200 video problem

[paul1981]

I finally took my 1200 apart and traced the video signal with my scope to the "-" side of C237 but not on R2340. My Ohm meter confirms the trace is open. I don't see the trace, maybe it runs in the middle of the board, which brings me to C236, a nearby surface mounted cap that was leaking (of course). I removed it and by one of the pads it looks like there is a hole in the board. Does this stuff usually eat right into the board? I can fix the video with a jumper. What should I put on the board to stop the corrosion? So far I just cleaned it with Iso-alcohol.

I use lemon juice, then clean up with IPA. Small boards you can get under the tap and rinse with water and a soft brush. And yes, it's normal that circuit boards get eaten by leaking batteries and capacitors unfortunately (both alkaline leakages).

[paul1981]

Yeah, I had some "stuff" from my TV fixing days in the 90's, but it dried up :-). I repaired a lot of broken boards back then, people were always dropping their TV's for some reason!! The traces were much larger on TV's back then than on a 1200 and my eyes were better. I started removing the other caps (two soldering iron method), but I'm not sure how I'm going to get the one beside the keyboard connector, very close to the socket.

The top of the keyboard connector unclips and lifts off, giving you a bit more room to get at those particular caps. Then use Kapton tape to heat shield the keyboard connector and the phono sockets. You should then be able to work quite liberally in that area.