Had (or have) a problem with my preamp
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muncybob
Posts: 2,972
So the other day I turned on my preamp and power amp to warm up a bit before putting on some tunes. Upon returninng to the house after 20 minutes or so and opening the front door I hear a loud hum coming from somewhere, thought it was the fridge. Then hum went away and the Mrs came from the tunes room to advise me the noise just started and to her credit she shut down the rig. After a process of elimination the culprit was identified as my tubed pre.
The extent of my electroinc knowledge is limited so all I did was jiggle a few wires while the hum was present hoping to find something not right, but no change. Then I replaced all the tubes (6) which didn't make sense to me but I was desperate. Well, the hum disappeared. So thinking it was one tube or socket, I slowly replaced each tube 1 at a time. Didn't prove anything because after all of the original tubes were reinstalled it was still dead quiet.
I was told it may be the power supply?
The extent of my electroinc knowledge is limited so all I did was jiggle a few wires while the hum was present hoping to find something not right, but no change. Then I replaced all the tubes (6) which didn't make sense to me but I was desperate. Well, the hum disappeared. So thinking it was one tube or socket, I slowly replaced each tube 1 at a time. Didn't prove anything because after all of the original tubes were reinstalled it was still dead quiet.
I was told it may be the power supply?
Yep, my name really is Bob.
Parasound HCA1500A(indoor sound) and HCA1000(outdoor sound), Dynaco PAS4, Denon DP1200 w/Shure V15 Type V and Jico SAS stylus, Marantz UD7007, Polk L600, Rythmik L12 sub.
Parasound HCA1500A(indoor sound) and HCA1000(outdoor sound), Dynaco PAS4, Denon DP1200 w/Shure V15 Type V and Jico SAS stylus, Marantz UD7007, Polk L600, Rythmik L12 sub.
Comments
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Maybe a tube has manifested a short.
Until I bought a tube tester I was just guessing. I had a CBS 5692 pair that one day out of the blue would start humming badly, fast forward to a year later reinserting the same pair of tubes I'm awakened one night with a loud thumping after the tubes were on for several hours. Testing those tubes after i got my tester it showed one as having shorts. So it had been going bad.
A tube going bad drawing excessive current could make a power supply angry one would think.
