Quote Originally Posted by Phillbo
Carl, I have an old Harman Kardon receiver that I use for the exterior speakers, It runs real hot and on occasion will drop one of the channels. I'm not much for tinkering with electronics (in truth, i should prolly kill the main breaker before changing a light bulb for my safety) but would like to try to diagnose before buying a cheapo to replace it . Any advice where to start ? I thought maybe opening it up and blowing it out real good to start.. An easy fix would be great but if not, i'll just trash it..
What I think is going on is that H-K's safety circuits are kicking in to prevent more damage. Better to shut down and cool down than burn out. For the last 25-30 years, most amplifier units (and microwave ovens) have had such circuitry. But something is out of spec on the channel that's going down (I assume it's always the same channel). It could be as small as a single resistor or capacitor that's blown. If you really love it and want to play with it, and have the test equipment, you could have a lot of fun. OTOH, you can buy a really nice two-channel receiver these days for under $100--today, Circuit City has a 100wpch Sherwood receiver for $75....You can't repair the H/K for that. They have an Onkyo surround sound for about $190.

Easy checks: Try the dusting out first. If it's full of dust, heat can build up. Be sure to check the power supply circuit--it should be near or connected to the power suppply transformer and be a smallish circuit board (if it's separate). Those components tend to throw heat.

Also you might check the power transistors and their heat sinks--they get VERY hot, too and if the sinks are dirty, they can't dissappate heat well. If the heat-conducting goop between the transistors and the sinks is shot or too thick, they'll overheat, too.

You could try a fan, like a PC fan, that's quiet to suck heat out of the unit, too. Might have to be inventive!

and try this sail boat on for size

http://www.pdracer.com/plans/harley-8.pdf
VERY cool! Norm, from This Old House and New Yankee Workshop built a small day-sailor as well, called a Clancy. I have the plans and video, but never built it. It's a little more complicated, but it's a similar idea.

http://www.newyankee.com/getproduct3.cgi?708