FDP Forum / Hum in the '64 White Knob Princeton.../ 4 messages in thread.

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super mario

Contributing Member
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USA

tone to the bone no other way
Dec 5th, 2016 09:56 AM        

Been using my regular amp in the Sunday services of late when playing electric guitar. No issues till this week when I plugged it in at home to work on some stuff and had a "steady hum" in the background. Nothing has changed at home wiring wise and I have played this amp for years with it being quiet. Now there is the hum....it is there even when the amp volume is set to 0, all other controls at 0 as well (this amp has a total of four controls: tone, speed, intensity and of course volume). For the tube amp gurus on these older circuits = thoughts on where to start the search. This amp still has the two-wire power cord setup but I am planning on making that update soon with a new three-prong plug setup. Just wanting to get thoughts on where to look first in regards to this "steady hum".



Hammond101

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So. Cal. USA

Dec 6th, 2016 07:12 PM        

I have more questions than answers for you but would suggest that if the amp does this plugged in at church or at home it is time for a filter cap can change. This hum is a warning that the cap can may fail causing other possible damage to the amplifier.<br /> <br /> If this has never been done it is long over due.



super mario

Contributing Member
*********

USA

tone to the bone no other way
Dec 6th, 2016 08:57 PM        

Hammond - I know it was "serviced" sometime in the late '70's but don't know if the cap can was changed. This was when my to-be Father in Law played it. He passed away in the mid-90's, long before I married into the family. Going to put it on the bench and begin checking it out....



Hammond101

Contributing Member
**********

So. Cal. USA

Dec 7th, 2016 06:45 PM        

If you have an ESR meter its an easy check. Even if the filter can was changed in the '70s it would again be time, overdue actually figuring a 20 year life. If you plan to play it swap it out. Mis-matched power tubes can also cause hum.



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