I have several pieces of tube gear. Today I notice one of my amps the power transformer seemed hotter that some of the other's.
With a thermal temp gun it is at 121 f.
My other amps and preamp are 98 to 117 f.
How hot is too hot, Or what should normal temps be?
Thanks
Ed
With a thermal temp gun it is at 121 f.
My other amps and preamp are 98 to 117 f.
How hot is too hot, Or what should normal temps be?
Thanks
Ed
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Modern insulation systems may be rated 200 deg C internal temperature.
Temp RISE is more useful than absolute. Texas? Some parts (tarpaper shack in the western ranges) may be 120F just air temp. Then 121 is only 1 degree hot, hardly nothing.
121F does not sound hot to me. I had Fishers which would slow-fry an egg.
Transformer is overheating
Google pulls up the Mercury Magnetics essay which is not wrong but super conservative and eager to sell you a new part.
Temp RISE is more useful than absolute. Texas? Some parts (tarpaper shack in the western ranges) may be 120F just air temp. Then 121 is only 1 degree hot, hardly nothing.
121F does not sound hot to me. I had Fishers which would slow-fry an egg.
Transformer is overheating
Google pulls up the Mercury Magnetics essay which is not wrong but super conservative and eager to sell you a new part.
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Hot transformer
The most important thing is the core temperature, which cannot be measured directly.
Attached is a PDF showing how to calculate the core temperature by the change of resistance method.
The most important thing is the core temperature, which cannot be measured directly.
Attached is a PDF showing how to calculate the core temperature by the change of resistance method.
Thanks for the feedback,
They are all Hammond and I measured the lams from the top looking down on them.
I guess I will open up one hottest and do some measurements.
At least it's not at me to down....
They are all Hammond and I measured the lams from the top looking down on them.
I guess I will open up one hottest and do some measurements.
At least it's not at me to down....
Is it noisy too? Excessive noise can be an indicator of a faulty tfmr as well as smell of coarse, but monitoring the current going in is a better indicator of something going wrong.
Andy.
Andy.
Hammond transformers, especially the newer versions are known to get hot. They don't tend to fail from that heat though. I have an Allied Electronics 6K7VG, built by Hammond in 2004, in my SSE amp.
I routinely run it over it's 150 mA spec on the HV winding. Typical current draw is about 180 mA and I have run it at up to 230 mA for hundreds of hours when I crank up the current for Depeche Mode or Pink Floyd. At that level you can't touch the transformer after a half hour and there is a "it's too hot" smell if it's been on for hours. This amp was connected to my PC for about 2 years and was on when ever the PC was on, which was a lot. That "science experiment" has not come to conclusion, the transformer is still working fine.
I have seen one Hammond fail and it had gotten rather wet in a hurricane but worked for several months, then died. Autopsy revealed a lot of rust and corrosion, indicating that it was still wet inside when I powered it on.
Two users have recently had exactly the same failure in new production Hammond transformers. The 5 volt heater winding became shorted to the 6.3 volt heater winding. This puts B+ on the 6.3 volt heaters making life miserable for several parts. Both SSE amps saw the 250 volt bypass caps short and smoke. Heat was not an issue here.
I routinely run it over it's 150 mA spec on the HV winding. Typical current draw is about 180 mA and I have run it at up to 230 mA for hundreds of hours when I crank up the current for Depeche Mode or Pink Floyd. At that level you can't touch the transformer after a half hour and there is a "it's too hot" smell if it's been on for hours. This amp was connected to my PC for about 2 years and was on when ever the PC was on, which was a lot. That "science experiment" has not come to conclusion, the transformer is still working fine.
I have seen one Hammond fail and it had gotten rather wet in a hurricane but worked for several months, then died. Autopsy revealed a lot of rust and corrosion, indicating that it was still wet inside when I powered it on.
Two users have recently had exactly the same failure in new production Hammond transformers. The 5 volt heater winding became shorted to the 6.3 volt heater winding. This puts B+ on the 6.3 volt heaters making life miserable for several parts. Both SSE amps saw the 250 volt bypass caps short and smoke. Heat was not an issue here.
Thanks Tubelab.
I am running this particular pair of amps pretty close the the transformers rating, but still under
What is troubling me is the difference between the two mono amps.
So I may a some point dig in
They are working well and sound fantastic, a pair of interstage coupled pp 2a3.
I am running this particular pair of amps pretty close the the transformers rating, but still under
What is troubling me is the difference between the two mono amps.
So I may a some point dig in
They are working well and sound fantastic, a pair of interstage coupled pp 2a3.
Most consumer parts are rated for a top temp. of 85C. That's way too hot to touch even for a short time. Of course, such high temps will shorted the lifespan of the parts, but the parts will meet their specs for a specified number of hours' use.
I am one of those users, and I can say I think George is right that heat was not the specific issue in my case. However, I should report that the transformer ran much hotter than I thought it should. I should also report that the Allied 6K7VG (also made by Hammond) that I installed in the same amp runs cooler than the Hammond did, despite being rated 50 mA lower on the HV winding.
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Transformer heat was always a question among Dynaco Stereo 70 owners just to talk about something. Everyone claimed the transformer was too small and produced too much heat. I've had numerous 70's after claiming to hate them I grew fond of them and began to play. I changed driver boards and people tried to tell me the newer board would overtax the transformer. They didn't take into consideration the fact the 70 was designed to be used with its mate a tube preamp which derived its power via the octal sockets on the front of the dynaco 70's face.
I played my modified 70's around the clock in extreme temperatures and never lost a power transformer in the process. So, my thoughts are as follows.... as long as the transformer and circuits it is feeding are operating correctly and not drawing excess current your probably ok. The transformers from back in the 40's and 50's were designed to run warmer probably due to the construction and insulation. If in question I would monitor the temp with an IR thermometer like I did until I was satisfied it wasn't going to burn up.
I played my modified 70's around the clock in extreme temperatures and never lost a power transformer in the process. So, my thoughts are as follows.... as long as the transformer and circuits it is feeding are operating correctly and not drawing excess current your probably ok. The transformers from back in the 40's and 50's were designed to run warmer probably due to the construction and insulation. If in question I would monitor the temp with an IR thermometer like I did until I was satisfied it wasn't going to burn up.
I have a Dynaco ST70 , I forgot about how hot they run.
I have not had it in my system in about a year.
It was in rough shape when got it, added the Tubes 4 hifi board, upgraded caps and bigger transformer.
I may pull it out and give it run and measure.
I have not had it in my system in about a year.
It was in rough shape when got it, added the Tubes 4 hifi board, upgraded caps and bigger transformer.
I may pull it out and give it run and measure.
What up, Willis?
Are people concerned about overheating transformers because their amps are turning red and melting?
With the exception of the 300B amp, all other transformers on my tube amps are older than the hills. Dynaco ST70, Fisher KX-200, TubeLab TSE-II running 45 tubes, TubeLab SSE, spud amp with 6CL6 output tubes, and two homemade amps with unknown origin power transformers that are most likely Hammand something or other.
After eight hours of operating, they're all hot. Hotter than a two-peckered goat. I like to think that the engineers who designed these devices designed them according to design criteria, such as how hot they could get before they cause a nuclear meltdown- a China Syndrome.
Relax. Play some music. If you have nothing better to do, get yourself a IR thermometer and take measurements every 30 minutes for an eight hour period. Make some graphs.
Without knowing the maximum operating temperature, your worries are unfounded. Unless your amp is going to be used for space flight or it will be in a museum display 500 years from now, it doesn't matter.
Are people concerned about overheating transformers because their amps are turning red and melting?
With the exception of the 300B amp, all other transformers on my tube amps are older than the hills. Dynaco ST70, Fisher KX-200, TubeLab TSE-II running 45 tubes, TubeLab SSE, spud amp with 6CL6 output tubes, and two homemade amps with unknown origin power transformers that are most likely Hammand something or other.
After eight hours of operating, they're all hot. Hotter than a two-peckered goat. I like to think that the engineers who designed these devices designed them according to design criteria, such as how hot they could get before they cause a nuclear meltdown- a China Syndrome.
Relax. Play some music. If you have nothing better to do, get yourself a IR thermometer and take measurements every 30 minutes for an eight hour period. Make some graphs.
Without knowing the maximum operating temperature, your worries are unfounded. Unless your amp is going to be used for space flight or it will be in a museum display 500 years from now, it doesn't matter.
have to understand how to read a data sheet.
They don't really come out and say this, but, those Hammond power transformer data sheets are assuming your DC supply is running in Full-Wave ; instead of Full-Wave-Bridge. Running Full-Wave puts the secondary coils running 50% duty-cycle, verses Full-Wave-Bridge puts the secondary coils running 100% duty-cycle.
They don't really come out and say this, but, those Hammond power transformer data sheets are assuming your DC supply is running in Full-Wave ; instead of Full-Wave-Bridge. Running Full-Wave puts the secondary coils running 50% duty-cycle, verses Full-Wave-Bridge puts the secondary coils running 100% duty-cycle.
Lol, awesome response Duke58
Not paranoid, they have been playing for months, on weekends 12 hrs a day or more.
Curious and just a concern at this point.
Pants not on fire...
Thanks
Ed
Not paranoid, they have been playing for months, on weekends 12 hrs a day or more.
Curious and just a concern at this point.
Pants not on fire...
Thanks
Ed
With the same DC load current, the difference between full wave that uses the center tap, versus a bridge across the whole center tapped winding is important.
That will make a large difference in the heating of the transformer.
With the same DC load current, this is also an important factor that affects the heating of the transformer:
Cap Input filter (hot)
Choke Input filter (cool)
Hammond provides a paper that shows the necessary derating of the current specs of their transformers:
1/2 wave, center tap full wave; bridge full wave.
And . . . Cap input filter; Choke input filter.
Read it, derate as necessary, and be happy.
Ignore it and get Hot Headed (because the transformer will be too hot)
That will make a large difference in the heating of the transformer.
With the same DC load current, this is also an important factor that affects the heating of the transformer:
Cap Input filter (hot)
Choke Input filter (cool)
Hammond provides a paper that shows the necessary derating of the current specs of their transformers:
1/2 wave, center tap full wave; bridge full wave.
And . . . Cap input filter; Choke input filter.
Read it, derate as necessary, and be happy.
Ignore it and get Hot Headed (because the transformer will be too hot)
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In my 1963 RCA Victor console, the power transformer runs HOT.... too hot to touch after a half hour of running.
It's got to feed 18 tube filaments, and supply HV to them, including the tuner chassis and amp.
Am I worried about it?........ nope.
The console's been running just fine since 1963, I leave well enough alone.
It's got to feed 18 tube filaments, and supply HV to them, including the tuner chassis and amp.
Am I worried about it?........ nope.
The console's been running just fine since 1963, I leave well enough alone.
All I can find (so far) is this https://www.hammfg.com/files/products/700/hammond-recitifier-guide.pdf which doesn't really specifically say anything about derating.