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Author Topic: Very noisy amp  (Read 1205 times)
KJ7YY
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Posts: 13




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« on: January 17, 2012, 05:47:24 PM »

I have an old Swan 1200-X that I have had in storage for years.  If I remember right, I am now 65 years young, it quit working and I just put it in a box and put it in storage.  I reciently dug it out and tried to fire it up.  Very loud buzzing the moment I turned it on.  On further review I found a burned resister between one of the tubes and what I think is the bias circuit.  I replaced the resistor and while I was inside I replaced all four of the tubes, 6LQ6s, and and all four of the filter caps too.  It still buzzes loudly so I shut it off after just a couple of seconds.
Maybe a transformer problem?  Any advice would be appreciated.  By the way, I found one of the filter caps installed backwards, I can't imagine any reason for this but I am sure it used to work.  There has been some modifications that are not in the owners manual.
Thanks in advance, John
KJ7YY
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W8JX
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« Reply #1 on: January 17, 2012, 06:05:34 PM »

Have you checked it for shorts and I did not see the rectifiers on the list either.
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KB4QAA
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Posts: 2269




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« Reply #2 on: January 17, 2012, 06:55:06 PM »

If you haven't already, replace the filter caps.  Decades old, they can only be bad or about to go bad. 
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KJ7YY
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Posts: 13




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« Reply #3 on: January 18, 2012, 03:26:02 PM »

I have not checked for shorts, but it didn't blow a fuse either.  I will check the rectifiers tho.  The filter caps are new.  Thanks for the help.  KJ7YY
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