M125 Power Transformer Normal Operating Temperature

I'm wondering if it's normal for the power transformers on the M125's to get very hot to the touch. After they are on for an hour or two, you can barely touch them. You can but must remove your hand quickly. Just want to make sure this is normal operation. I'm running Weber copper caps and Tung-Sol KT120's.

Thanks!

Thanks Bob for directing me to that information. I'll add it to my hard copy documentation.
The amps are sounding great!

Frank.

if one thinks about it, tube audio gear is incredibly resilient! The temperatures that this gear works at, tubes in excess of 300F+, transformers way over 100F, think about it, those are cooking temps for your roast!
Most SS gear, if not properly heat sinked, would have given out long before temps of 300F+!
As worrying as some of these temps look, tube gear will just plod along playing your favorite music!

MontanaWay, it is amazing when you realize the heat these amps continuously have to experience. And resiliency is one reason why I decided to invest in these amps. I want reliability and serviceability for decades to come.

I've done a lot of restoration work on radios from the 1930s through the 1950s. With capacitor replacement, they work amazingly well. I've looked at many a chassis wondering just how many hours they have already be run. And they still work. Something about that appeals to me.

I have some EH Scott Radios from the 1930s that were top shelf in their day. This was audio
during the great depression. Still very good performers and with the exception of replacement capacitors and a few out of spec resistors, the rest including transformers are still working fine some 80 years later!

I posted a photo with VTA 70 temps as part of my Picasa pictorial last year. Note the ambient room  temp. of 78F.


VTA ST-70 temps


Since then, I have rolled in a completely different tube set, but I think the temperatures would be comparable.

Gregg R.

Frank...you heard it from the horses mouth...run with it!
I have the m125's and the heat element from the transformers doesn't bother me since there is also the heat radiating from the output and driver tubes to take into consideration.
Also I believe location is very important.
My 125's are on an open stand...free to breath.
I am also using the Weber WZ68 and the KT88's

Frank F

Hello everyone:  I have finished the assembly of my amps in July. they are wonderful amps, were totally quiet amps with no noises in the speakers.
but now I detect 120hz noise in both amps its not very loud mind you, and it does not effect there ability to make great sound. It does bother me that they
only have about 60 hours on them, and starting to act up!
  I have changed out the drivers and swapped out output tubes to no avail. It reminds me of a device with not enough capacitance. the right amp has a little more noise than the left
I have cheaters on both, so no ground loops.
 One thing that did help was to half power the amps(two output tubes) . I was going to do this anyway ( I live in Tx its hot) the AC handles them better this way. There is less 120hz now
but still there.
What would happen if you were to lose one choke or one section of the cap? the other choke would probably burn up.
Bob talks about doing a hum balance procedure. could this be the problem?  Oh I also changed the rectifiers with no difference. I done all I could without breaking into them with a meter
please help? suggestions.

Don't forget to try reversing the two prong cheater plug in the wall socket and see if that helps. Possible the cord was hooked up backwards internally. That's a common fix for residual hum in a lot of the older two wire equipment.

If the cheater plug has the wide blade on one side, you can cheat by snipping the ears off the wide blade. It's almost like they had that in mind when they designed the things ... but ... that would be cheating!

Hi all:
well the poblem is certanly NOT the M125's . I preformed the shorted input test with all tubes incerted They are realy very very quiet.
the problem is in my V.T.A. SP14 pre amp. I have had trouble befor with its power supply. I guess i did not notice it when it was hooked up to my SS amplifier the SS is not as responsive as the M125"s , The M125's tend to have higher output.

I would like to ask Bob if he could post the pictures i sent of my build I have no way to do this. I had to use someone elses computer to send them to Bob so i do give permission to post them. Thanks.
I will get my pre amp quiet again. Maybe that is just the way it is. with backround power supply noise. NOT!!!

Oreme69 - your SP14 preamp should be DEAD quiet.
Email me directly (click on my name, and click on send email or PM), we'll figure out what is causing the problem . . .

oreme69, when you determine what the problem was, could you post the solution?
Did it sound sort of like a guitar amp with the cable disconnected from the instrument?