I have recently repaired an old soviet Amplifier, which uses a High power transformer.
The transformer seems to be making a Humming sound , which i should say is very annoying, the Humming sound & vibration is not loud though, but an irritating one.

Any advises or recommendations to get rid of this problem will be deeply appreciated.

 

This can happen with E-type laminated cores. Here in the USA, they used to use a shellac as a sort of an adhesive to keep the laminations in place. It may be that the material used in your transformer has aged and cracked, so the laminations can once again vibrate against each other, making a humming or buzzing noise.

I do not know what type of material to recommend that you use, as I have no idea as to what you may have access to in the Ukraine.

Lacquer would not be a good choice, as it may dissolve the insulation on your windings, which would destroy the transformer.

 

This can happen with E-type laminated cores. Here in the USA, they used to use a shellac as a sort of an adhesive to keep the laminations in place. It may be that the material used in your transformer has aged and cracked, so the laminations can once again vibrate against each other, making a humming or buzzing noise.

I do not know what type of material to recommend that you use, as I have no idea as to what you may have access to in the Ukraine.

Lacquer would not be a good choice, as it may dissolve the insulation on your windings, which would destroy the transformer.

Thank you for your quick response.

Understood, So this means that the PSU is fine , no problem with the rectifier or other capacitors, its just the adhesive which might have aged. Is it ok if i continue using the transformer in its current (humming) status ?

 

Depending on your skill level, I would consider opening it up, and lightly driving (pressing) some very small wooden shims between the windings and the core. That is what they do when they re-wind transformers and the new winding is too small. It's just vibration, but could possibly lead to wear and shorting in the future, in my opinion.

Post a photo if you can, so we can see how you would take the bell covers off (if possible).

Another idea is to "pot" it in wax, but you'd have to know how hot that trafo will get, and whether the wax will stay solid at the operating temperature...I'd go for shims.

 

I have an older Yamaha amplifier that began transformer buzzing a few years ago. The problem appeared to be deteriorating shellac as the Sgt. mentioned. I cut various shapes of mylar (plastic sheet) and wedged them inside the transformer to minimize the vibration. The buzzing was greatly reduced though not completely eliminated.

creakndale

 

Depending on your skill level, I would consider opening it up, and lightly driving (pressing) some very small wooden shims between the windings and the core. That is what they do when they re-wind transformers and the new winding is too small. It's just vibration, but could possibly lead to wear and shorting in the future, in my opinion.

Post a photo if you can, so we can see how you would take the bell covers off (if possible).

Another idea is to "pot" it in wax, but you'd have to know how hot that trafo will get, and whether the wax will stay solid at the operating temperature...I'd go for shims.

Thank you for your useful quote.
I have attached a picture of the transformer with this reply, please check the same.
I would also prefer using the "Shims" method, as i think "Potting" the transformer in wax will be a risk taking factor for me.

 

While it's operating and buzzing, use a wooden stick (popsicle stick) to push on all the pieces that make up the transformer assembly. When you find a spot where the buzzing volume increases and decreases with applied pressure, that's where you want to add a shim.

Make sure all the screws that hold the transformer assembly to the chassis are tight.

At worse case, you might need to unscrew the transformer assembly from the chassis and add some dampening material between the transformer plate and the chassis.

creakndale

 

First easy fix is to just tighten all the bolts.
It sometimes makes a difference.

 

While it's operating and buzzing, use a wooden stick (popsicle stick) to push on all the pieces that make up the transformer assembly. When you find a spot where the buzzing volume increases and decreases with applied pressure, that's where you want to add a shim.

Make sure all the screws that hold the transformer assembly to the chassis are tight.

At worse case, you might need to unscrew the transformer assembly from the chassis and add some dampening material between the transformer plate and the chassis.

creakndale

Thank you ,
will work on it & update.

 

First easy fix is to just tighten all the bolts.
It sometimes makes a difference.

Sure will start with bolts first, if still the humming/vibrating continues , then will proceed using "Shims" method.

 

For many (many) years ago I salvage a big transformer from some computer equipment. I remember it had a big 250uF high voltage cap (ca 400 v) connected to it. Without this capacitor the transformer was humming and vibrated more than expected. It was also getting somewhat hot. But with the capacitor everything was as normal. I do not know how this capacitor was connected to the transformer. But perhaps you need something like this, and that other members can explain why and how.

 

For many (many) years ago I salvage a big transformer from some computer equipment. I remember it had a big 250uF high voltage cap (ca 400 v) connected to it. Without this capacitor the transformer was humming and vibrated more than expected. It was also getting somewhat hot. But with the capacitor everything was as normal. I do not know how this capacitor was connected to the transformer. But perhaps you need something like this, and that other members can explain why and how.

Thanks a lot for your quote,
In fact i myself was planing to change the Capacitors & the rectifier in the PSU.
Now after your quote i will do that in the first place.

 

Be careful, but this should be pretty easily correctable. )

 

Hello,

Changed all the 2200uf capacitors & the rectifier chip in the PSU, the humming sound has considerably reduced.