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Old 19th January 2011, 11:39 AM   #1
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Default Help!Transformer overheating!

Hi guys,
I rebuilt one channel of this stereo amp,2 pairs in quasi comp.Now the amp is working but the trafo gets warm when listening at normal levels but the copper wires remain cool.When i push it a little louder for about 4-5 hours it really heats up and the winding heats up too.There's no detectable change in sound quality when it heats.
Should i worry about the heating?Can it affect the life of the trafo too much?
Regards.
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Old 19th January 2011, 11:45 AM   #2
AJT is offline AJT  Philippines
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how hot is hot? if you can hold on to your traffo for 10 secs without feeling pain, then your traffo is probably ok.....
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Old 19th January 2011, 11:54 AM   #3
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What is the transformer's power rating ('VA') and how much power are you actually drawing from it (measure; don't guess)?

In general, a transformer shouldn't heat up. If it does, it is probably being misused or operated near its maximum capacity. The latter is rather unlikely with most audio amplifiers run on living room volumes.
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Old 19th January 2011, 12:20 PM   #4
AndrewT is offline AndrewT  Scotland
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I expect all my transformers to run cool.
Many Members say I am too conservative.
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Old 19th January 2011, 12:24 PM   #5
AJT is offline AJT  Philippines
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i design all my transformers to run cool, however commercial transformers are designed to optimize use of copper, most often than not, that is not in agreement with a cool running traffo unfortunately...
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Old 19th January 2011, 01:33 PM   #6
DF96 is offline DF96  England
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What does "rebuilt" mean? Why only one channel?

The main problem with hot transformers is insulation breakdown, which may or may not be accompanied by release of magic blue smoke. Modern transformers can cope with high temperatures if they are well built. Not all modern transformers are well built, especially from certain parts of the world!
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Old 20th January 2011, 10:15 AM   #7
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I was looking for a transformer but i couldn't find a cheap new one.I found an old one at a radio shack,the guy made me an offer i couldn't refuse:a 3"*4"*10" heatsink + an old pcb from a '91 pioneer amp for less than 5$.
It turned out that one channel was smoked out and i needed a mono amp,so i changed the outputs and added another pair. The original outputs were a pair of 2955's & 3055's per channel with a +/-50v supply,so i figured out the power was around 70-90 watts into 8 ohms.2 pairs of 5200's into 4 ohms with the same psu would give me around 150-180 watts,this wouldn't be overloading the psu, would it?Maybe am overlooking something?I stand for corrections.
I already fixed a 12 v fan from a computer psu,i don't know if it will help,i haven't pushed it yet.
I have a crappy dmm it shows nothing when i try to measure current.
Regards.
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Last edited by xeclipse; 20th January 2011 at 10:23 AM. Reason: note
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Old 20th January 2011, 10:20 AM   #8
AJT is offline AJT  Philippines
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do you have dimensions of your traffo or picture we can look at?
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Old 20th January 2011, 10:39 AM   #9
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Quote:
Originally Posted by xeclipse View Post
Hi guys,
I rebuilt one channel of this stereo amp,2 pairs in quasi comp.Now the amp is working but the trafo gets warm when listening at normal levels but the copper wires remain cool.When i push it a little louder for about 4-5 hours it really heats up and the winding heats up too.There's no detectable change in sound quality when it heats.
Should i worry about the heating?Can it affect the life of the trafo too much?
Regards.
If it doesn't overheat when running at low volume I would doubt that you have any shorted turns.
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Old 20th January 2011, 10:43 AM   #10
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Quote:
Originally Posted by Tony View Post
do you have dimensions of your traffo?
EI core measures 2.75 * 3.25 *
2.75 inches and weighs over 3.5(<4) kgs
(7.7 pounds).
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