CPC464 with intermittent brightness issues

[darkhalf]

This one is a tall key CPC464 with the older gate array (with heatsink on top) so 40007/8. This was an 'untested' unit which arrived with dead Z80 (replaced) but shows subtle intermittent changes to brightness occasionally


Anyone got any ideas what might cause this, or where to start looking? Mainly noticeable with blue but have seen with green/red too, so the luminance signal is probably affected. I can scope the signals if required


I've seen the problem on different monitors, so its not that monitor. Thanks

[Kris]

Looks like a dried welding point, check this point on the main board.

[Bryce]

Could be a break in the spiral cable, dirt on the monitor socket pins or dodgy solder joints on the monitor socket. Check them all.

Bryce.

[darkhalf]

Thanks for the replies.


The spiral cable is part of the monitor (CPC6128 plugged in does not show issues on either) and I've used contact cleaner on the DIN socket. I'll go through the joints around the connector/gate next