Power Transformer Getting Hot

Cassady · May 8th, 2008, 08:06 AM

Is it normal for power transformers in a tube amp to get hot? I'm not talking about smoking, something's burning up hot, but uncomfortable to touch hot?

After playing for about an hour and a half last night while I was trying out a couple of new guitars, I noticed that the power switch was hot when I turned it off. I reached inside the chassis to see if my transformers were hot and, sure enough, the power transformer was hot.

TIA

Cassady

DADGAD · May 8th, 2008, 08:48 AM

They will get pretty warm. If it's too hot to leave your hand on, it's running over 150 degrees F. If so, have it checked by a qualified tech as the bias could be too high, a faulty filter, tube or other problem.

Tube amps that are used regularly should be checked about every 6 months.

4 Strings · May 8th, 2008, 01:16 PM

+1 on the possibility of faulty filter caps. If it is an old amp which has not been re-capped, consider doing a cap job!

My SF Bassman 100 runs a little too hot for comfort and should propably benefit from a cap job. By power of its age it sure deserves one by now. But until I get around to re-cap it I have simply pulled the pilot light and the unused 12AX7 v1 out. Not that it makes very much difference and it certainly isn't the most elegant of makeshift solutions but I imagine it takes some stress off of the PT.

May 8th, 2008, 08:06 AM	#1 (permalink)
Cassady Tele-Holic Join Date: Jan 2005 Location: Lincoln, Nebraska Posts: 548	Power Transformer Getting Hot Is it normal for power transformers in a tube amp to get hot? I'm not talking about smoking, something's burning up hot, but uncomfortable to touch hot? After playing for about an hour and a half last night while I was trying out a couple of new guitars, I noticed that the power switch was hot when I turned it off. I reached inside the chassis to see if my transformers were hot and, sure enough, the power transformer was hot. TIA Cassady

May 8th, 2008, 08:48 AM	#2 (permalink)
DADGAD Tele-Holic Join Date: Mar 2003 Location: Palmdale, CA Posts: 764	They will get pretty warm. If it's too hot to leave your hand on, it's running over 150 degrees F. If so, have it checked by a qualified tech as the bias could be too high, a faulty filter, tube or other problem. Tube amps that are used regularly should be checked about every 6 months. __________________ "I need to learn some new scales and stop obsessing about this stuff." http://www.myspace.com/slickshoes

May 8th, 2008, 01:16 PM	#3 (permalink)
4 Strings Tele-Meister Join Date: Jun 2007 Location: Gossip County Posts: 253	+1 on the possibility of faulty filter caps. If it is an old amp which has not been re-capped, consider doing a cap job! My SF Bassman 100 runs a little too hot for comfort and should propably benefit from a cap job. By power of its age it sure deserves one by now. But until I get around to re-cap it I have simply pulled the pilot light and the unused 12AX7 v1 out. Not that it makes very much difference and it certainly isn't the most elegant of makeshift solutions but I imagine it takes some stress off of the PT. __________________ We shall not cease from modifying our amps. And the end of all our modifying will be to arrive where we started and know the circuit for the first time.