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    M125 Power Transformer Normal Operating Temperature

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    Frank111

    Posts : 84
    Join date : 2015-02-23
    Location : Minneapolis/StPaul Area

    M125 Power Transformer Normal Operating Temperature

    Post by Frank111 on Thu Jul 02, 2015 8:37 am

    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!

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: M125 Power Transformer Normal Operating Temperature

    Post by Bob Latino on Thu Jul 02, 2015 9:33 am

    Frank111 wrote: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!

    Hi Frank,

    Almost every year about this time this subject comes up .. As the ambient temperature in your home gets higher in the summer, the air around the amp is warmer and the amp has more trouble getting rid of the heat. As such, the amp runs a little warmer. This won't hurt the amp. The power transformer can get up to 140 degrees .. Check out my post from May of 2011 at the link below and the photo of temperatures of a VTA ST-120 ...

    Tube amp heat in warmer weather

    Bob

    Frank111

    Posts : 84
    Join date : 2015-02-23
    Location : Minneapolis/StPaul Area

    Re: M125 Power Transformer Normal Operating Temperature

    Post by Frank111 on Thu Jul 02, 2015 9:38 am

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

    Frank.

    MontanaWay

    Posts : 781
    Join date : 2014-02-06
    Age : 58
    Location : Brookings, Oregon

    Re: M125 Power Transformer Normal Operating Temperature

    Post by MontanaWay on Thu Jul 02, 2015 11:02 am

    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! affraid
    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!

    Frank111

    Posts : 84
    Join date : 2015-02-23
    Location : Minneapolis/StPaul Area

    Re: M125 Power Transformer Normal Operating Temperature

    Post by Frank111 on Thu Jul 02, 2015 11:18 am

    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!

    Gregg R.

    Posts : 78
    Join date : 2014-02-20
    Age : 72
    Location : Land of 11,842 Lakes

    Re: Transformer temps, etc.

    Post by Gregg R. on Fri Jul 03, 2015 1:37 am

    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.

    bluemeanies

    Posts : 129
    Join date : 2015-02-09
    Age : 66
    Location : Folsom Pa.

    Re: M125 Power Transformer Normal Operating Temperature

    Post by bluemeanies on Thu Jul 09, 2015 6:58 pm

    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

    orome69

    Posts : 2
    Join date : 2015-08-05

    m125 hum problem

    Post by orome69 on Thu Aug 20, 2015 7:27 pm

    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.

    Bob Latino
    Admin

    Posts : 2411
    Join date : 2008-11-26
    Location : Massachusetts

    Re: M125 Power Transformer Normal Operating Temperature

    Post by Bob Latino on Thu Aug 20, 2015 7:51 pm

    To check for noise in the amps do this .. Disconnect the interconnects at your preamp. Hold the two ends you just removed from your preamp together. Now use the metal shaft of a screwdriver to short between the center pin and the outer shield of both interconnects. Listen to each amp now. What you hear is the residual noise level of the amps.

    If there is still noise then you may have a "ground loop". This can happen if  ...

    1. Any other component in your amp ALSO has a 3 wire power cord.
    2. The ground on your home AC line is not grounded properly.
    3. You have the ground for your TV's cable on the same line.

    Try floating the ground on each amp by using a 3 to 2 "cheater plug". This will remove the ground as a possible cause of the noise/hum.

    Let us know what you find ?

    Bob

    sKiZo

    Posts : 1308
    Join date : 2013-04-01
    Location : Michigan USA

    Re: M125 Power Transformer Normal Operating Temperature

    Post by sKiZo on Fri Aug 21, 2015 2:12 pm

    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! clown

    orome69

    Posts : 2
    Join date : 2015-08-05

    Noise results from previous posts

    Post by orome69 on Thu Aug 27, 2015 7:59 am

    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!!!

    tubes4hifi
    Admin

    Posts : 1282
    Join date : 2008-11-30

    Re: M125 Power Transformer Normal Operating Temperature

    Post by tubes4hifi on Sat Aug 29, 2015 7:04 pm

    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 . . .

    Frank111

    Posts : 84
    Join date : 2015-02-23
    Location : Minneapolis/StPaul Area

    Re: M125 Power Transformer Normal Operating Temperature

    Post by Frank111 on Tue Sep 01, 2015 7:57 am

    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?

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