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Krell KAV 300i problem

H

hmavunduk

New Member
Hi, everyone,

My beautiful Krell KAV300i has some issue that I hope somebody here can address the problem. Well, I can explain the problem as follows;

1- Amp is on all the input jacks are empty, when I get closer my hands or touch one of the input RCA jacks a very high, annoying hum starts

2- Amp is on and I play something thru one of the single ended inputs without having a problem. But when I switch to an empty input channel that annoying hum starts again and never stops.

This probably happens to be a grounding problem and just have occurred very recently. I have another system using same AC outlet showing no problem at all. I also tried this amp in another room but the problem was still there.

I'd like to have comments on this.
Thanks.
 
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Greetings and welcome to AK.

Schematics? hmm I'd start with the power cord. You are acting as the 'ground' potential, might also be a bad ground or case isn't tight with the screws. if the cord is "flimsy" or rubbery? Second is probably in the power supply section.

edit; third is maybe a bad neutral.. to ground on the rca;s. maybe some bad or old soldering, too.
 
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Thanks for your reply.
My power cord is almost new and a nice one. Do you think the caps in power supply section might be the problem. At least one of them, knowing that my amp is from 1997.
 
The input/preamp board sits above the main amp board. It gets power and i think maybe ground as well through the metal standoffs its mounted on. There are also long pin connectors that connect the signaling from the preamp board to the amp board. Its possible there is a bad ground connection there. You might try making sure the stand-off screws are tight and the the long pins are making good connections.
 
Thanks. I actually took preamp out for checking. May be, I should clean these long pins up. This thing drove me crazy.
 
I just found that 'preamp out' jacks of the amp shows short circuit when I check them with a multimeter. Is that normal? If not what would be wrong?

(I actually took out preamp section before checking)
 
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