Noisy Transformer solutions

Question

I have a power transformer from an old solid state guitar amp from the 70s and it is extremely noisy. I isolated the issue in the sense, that I took it from the device, stripped it from its case and powered it without load. The loud buzz still occurs.

Now it seems difficult to find a direct replacement transformer that delivers 52VAC on the secondary with 230VAC on the primary and the right power rating. Therefore I see two options. Either pot the thing or rewind it all together.

What would you suggest? And depending on your answer, could you point me to appropriate resources?

Answer 1

Rewinding is not indicated; the noise is most likely coming from the core, not the windings.

There are a couple of things you can do to mitigate this, especially if the core laminations are visibly loose. One quick thing to try if the core has through-holes is to put long screws through the holes and tighten them down.

Another thing to try is to disassemble the core from the windings and soak it in lacquer to keep the laminations from vibrating against each other. After you soak it, squeeze any excess out in a vise as it dries.

One more thing to try (if you have the resources) is to clamp the core in a vise and run a bead of arc-welding across the laminations on one or more sides. You'll sometimes see this in transformers as they come from the factory.

If it turns out that the problem IS in the windings, you could try soaking them in lacquer, too.

One other thing to try: If there's room, drive thin wooden tapered shims between the core and the winding assembly. This will both compress the core laminations and stretch the windings, hopefully reducing vibration in both.

Answer 2

I used to pour a thin 2-part urethane in noisy transformers. Worked well for the transformers we used.

Answer 3

I presume this is laminated steel not a large ferrite donut.

Show the construction type with an equivalent web shot or photo. The excitation current with no load causes 50 , and harmonic forces that can excite vibrations in xxx micrometer motion. How does it sound? More Buzz than hum? What dimensions? Does any pressure affect it?

A lacquer tank dip is hard to get good seepage unless you can draw a vacuum into the voids. Even a vacuum cleaner hose with a coffee paper filter in a case is better than nothing with vibration. That otta doit.

The power rating (VA) can be estimated from the core weight.

Answer 4

I have successfully reduced (not eliminated) the buzzing in smaller units by remounting the transformer using some rubber grommets to reduce mechanical coupling to the case.