The Case of the Cap and Bus Conflict

By Kirk Brodeur

I have a Kenwood VR705 receiver that died completely (No power). Initial inspection found the main input fuse blown. So I ordered a schematic and went to work. While tracking down the short causing the fuse to blow I discovered a shorted C142. I was shocked to see a 75V cap on a 76V bus.

It was easy to spot the bad component as the top and sides of this capacitor were bulged out quite a bit. I understand cost cutting but when did it become OK to use parts not even rated for the job? This wasn’t the only place they cut corners. Notice the 42V cap on the 46V bus!!!! Adding to the problem was the AC supply in my house which is closer to 125V. So rather than being 1V underrated it was closer to 10V.

I’m surprised this lasted the couple of years that it did. Now I can’t even fix the problem because you can’t get a new capacitor rated for the job that fits in this footprint. Needless to say I was pretty disappointed in this product’s quality. Often on this forum you hear folks talking about how you get what you pay for. This was one of the more expensive units they had at the store. Seems this logic doesn’t always apply.

Kirk Brodeur. has worked in the electronics industry for 15 years. He spent several years working variable speed AC motor drives. He currently work at EMC managing their Systems Test Engineering department. He has also worked at EMC as a Failure analysis engineer.