Compaq Portable - display loses sync - display garbage temporarily

[alank2]

It works 99% of the time, but it will occasionally just for a blip lose sync and/or display junk for a moment.  I'm not sure if it is the monitor or if it is the video board, I suppose it could be either.  Any recommendations on what to look at first?

[CJay]

Could well be both but I'd start with the video card, which Compaq Portable is it?

[alank2]

It is the original compaq portable - 8088  with a pair of 360K floppy drives.  The monitor is an odd thing where it can do dual signal - you can press ctrl-alt-< for MDA and ctrl-alt-> for CGA and it will change the display.  The MDA looks much better with 9x14 characters, in CGA mode I think it has 8x8 characters and you can see scanlines.  The video card is a full length and connects to the monitor with a 2x5 100 mil header.

[james_s]

These were quite unique machines. The dual mode card supported CGA for compatibility reasons and could output color to an external monitor but the built in display was monochrome. I would start by carefully inspecting the cable to the internal monitor and if that looks ok you might have a cracked solder joint in the monitor itself. If you have an external CGA monitor to try see if that exhibits the loss of sync, or you could put a scope on the sync signals.

I had one of these once, complete with a nice padded carry bag. Sometimes I wish I'd kept it.