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My 299C gets hum on phono input but no hum on tuner/extra. The hum is increased by volume control and when I touch the chassis, it is gone. I know it is ground loop hum but I don't know how eliminate it.Any suggestion would be appreciated.
I have replaced the bridge rectifier, coupling caps and filter caps.
Thanks.
Follow Ups:
Hi guys,Thank you for all suggestion.
My amp hums WITHOUT ANY AUDIO CONNECTED to it except the speaker. I have checked my turntable and it is fine. The hum is from the amp itself.
Thanks.
Doom
Is it humming thru both channels?.Also did you try shorting the inputs with just a pair of inner connects plugged in and then short across them? If it still happnens you have an input issue to the 1st stage of the phono most likely and I have seen the 47k resistors open up on occasion or change value dramatically.
Michael,Yes hum on both channels. Can you show me where the 47k resistor located ? I am still confused. Thanks
Anti
Email me at merccougar89@yahoo.com and I can call you as I have free long distance and I can talk you thru it over the phone.If you have long distance you can call me but it doesnt cost me a dime..What you need to do is turn the chasis upside down and look for the yellow violet orange resistors going to the 12ax7 tubes for the phono stage.Usually the input jacks for the phono go to these resistors and then to the grid of the tubes..If you have an instant messenger I can talk you thru it on that to but its a lot easier over the phone..I dont teach school tommorrow so I will be up a while tonite.
mikey
Does it hum when the turntable is not connected, or only when it is?Does it hum when you have the cover on? (Some useful shielding may be provided. I've got a phono stage that's placed upright at rear of receiver with a metal shield on the inside of the board, attached to the bracket; the shielding for the outside is done by the cover. Hence, it hums a lot more w/ cover off.)
Steve.
Have you tried reversing the AC plugs in their outlets? Is the TT plugged into an accessory socket on the back of the amp, or is it plugged into the wall?If you haven't done that yet give it a try, reversing one at a time.
Thank FisherdudeI have tried reversing the AC plugs in the AC outlet. It still hum even nothing connected to it.
Help please
Could this be something to do with your turntable? I had the problem once and it turned out my table wasn't properly grounded. It LOOKED like it was, the ground wire was attached to the amp like it was supposed to be. After I tried a hundred different things and frustrated myself, I opened up the bottom cover of the turntable and found that the ground wire was loose, inside of the turntable. Resoldered that and the hum was gone.You might also have a bad connection at the cartridge. If you have another turtable or could borrow one that might help narrow down the problems.
Jon
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