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.
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.
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.
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.
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!
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!
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.
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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If it doesn't overheat when running at low volume I would doubt that you have any shorted turns.
I would expect a +-50Vdc PSU to eventually, or quickly, blow a pair of 2955/3055.
It's an accident waiting to happen.
+-35Vdc to +-40Vdc would be a safer choice for those devices.
i'd say 180 watts is too optimistic for that size traffo, what are your rails?
How much power do you estimate it at?What about the VA?
I couldn't find genuine A1943's...just C5200's.
Generally the maximum power that a transformer can transfer from Primary to Secondary is given by the formula:
Core Area = (Square Root of 110% Watts) / 0.0086
If you measure the cross sectional area of the centre leg of the transformer in mm^2
Then Max Power = (Area * 0.0086) ^ 2.
This is then derated by 10%.
I'm making some assumptions here:-
Core Area = 1200mm^2
Max Power = 100VA
Of course the windings may be insufficient to handle this power.
These maths are for Military Grade Transformers using a maximum Flux of 860mT. Our Oriental friends often push the envelope and don't design for 200% reliability as do the MoD.
Core Area = (Square Root of 110% Watts) / 0.0086
If you measure the cross sectional area of the centre leg of the transformer in mm^2
Then Max Power = (Area * 0.0086) ^ 2.
This is then derated by 10%.
I'm making some assumptions here:-
Core Area = 1200mm^2
Max Power = 100VA
Of course the windings may be insufficient to handle this power.
These maths are for Military Grade Transformers using a maximum Flux of 860mT. Our Oriental friends often push the envelope and don't design for 200% reliability as do the MoD.
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However, pulling more power would only cause the windings to overheat and the transformer to lose regulation.
Core overheating without winding overheating may be due to poor construction or the laminations being shorted together. Ideally the laminated Es and Is should all be insulated from each other by a varnish or oxidised insulating coating. This can be compromised by the mounting bolts fixing the transformer.
Core overheating without winding overheating may be due to poor construction or the laminations being shorted together. Ideally the laminated Es and Is should all be insulated from each other by a varnish or oxidised insulating coating. This can be compromised by the mounting bolts fixing the transformer.
In normal construction the secondary is at the centre of the transformer with the primary on the outside, unless it is a split bobbin design.
In such a case the secondary could well be overheating and heating up the core, the primary is insulating it so you're not really feeling the heat from where it is being generated.
If you can keep your finger on it for more than 10 seconds it is probably less than 50 degrees C. Not ideal for long term reliability. Transformers should normally run fairly cool.
In such a case the secondary could well be overheating and heating up the core, the primary is insulating it so you're not really feeling the heat from where it is being generated.
If you can keep your finger on it for more than 10 seconds it is probably less than 50 degrees C. Not ideal for long term reliability. Transformers should normally run fairly cool.
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