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ARC REF 150 Buzzing noise

I have an ARC REF 150 amp with over 4000 hours on it, and recently it has developed a buzzing noise.  This appears after about 30 minutes of use, and seems to get steadily louder.  I thought it might be a tube.   I had KT150 power tubes in it and I swapped those out  for KT120's and re-biased.  No change.  I then swapped out the 6H30 input tubes and re-biased again.  Buzzing is still there.  It is very difficult to locate the sound on the boards.    I have also had several blown fuses, this has been in the midst of a move and may or may not be reIated to the buzzing.  I have to assume this needs a repair, but I am wondering if anyone has a guess or even better, experience with the problem.  I am in the Denver area and if anyone knows of a local repair opportunity, I would appreciate knowing that too.  I do not look forward to the expense and delay of sending it back to ARC repair.  Thanks.  Scott
scottwsmith

Showing 1 response by minorl

minorl
1,018 posts
 
An educated guess but I think you may have damaged the transformer by using KT150 tubes.if this t
is the non SE REF 150 then according to Audio Research to upgrade to SE and use KT150’s some major upgrades needed to be done,including replacing the transformers.

i would put the KT120 tubes back in it and send it to Audio Research for evaluation, inspection and repair.  Also,find out how much to repair and how much to upgrade to SE.  it might be the same price if you have to change the same transformer
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