I think this site here is a pretty good one as there are techs who work on equipment for their trade here as well as just for own enjoyment...here is also one I remember reading a while back but have not looked at it in depth for a while
http://www.anatekcorp.com/
And there is
http://www.badcaps.com for bad cap problems especially on computer motherboards.
IF you are into arcade game/monitor repair and other coin op equipment, here is a good one that used to be free but you need to subscribe now to access it:
http://www.startechjournal.com/