I have a old Kenwood reciever/amplifier that I usually use that lately has had some issues with what I could best describe as "pocs" coming out of the speakers, as in some sort of noise. While I'm not much of a EE by any means, I went through and did some basic checks, such as testing the grounds, along with testing compents in the power supply area. However, what I found interesting is that the two largest caps, some electrolytics 80V @ 7500uF, seemlying are magically charging themselfs 
. Basically I unplugged the amp, and removed the PSU board. The only thing left connected to the PSU board is the transformer's primaries which aren't removable without desoldering. The two caps had about 20V left over, so I shorted the postitive to a ground on both caps, then retested to check for voltage. When I hooked up the multimeter I noticed that the voltage was going up, and rather quicky, about 10V/minute. There is some smaller electrolytics on the board, but none of which contain any voltage. So being the amplifer is unplugged, what exactly is charging these caps?
. Basically I unplugged the amp, and removed the PSU board. The only thing left connected to the PSU board is the transformer's primaries which aren't removable without desoldering. The two caps had about 20V left over, so I shorted the postitive to a ground on both caps, then retested to check for voltage. When I hooked up the multimeter I noticed that the voltage was going up, and rather quicky, about 10V/minute. There is some smaller electrolytics on the board, but none of which contain any voltage. So being the amplifer is unplugged, what exactly is charging these caps?Hi, Moses, this is nothing magic, but classic ageing behaviour : the electrolytic caps get "dry" and the internal resistance increases, so you cannot discharge them completly... The same effect can be found on new ones, high voltage models for instance...
You will find a great improvement in the sound of your receiver after having changed all the electrolytics for new ones, I think...
You will find a great improvement in the sound of your receiver after having changed all the electrolytics for new ones, I think...
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