Repairing/replacing a humming toroidal

[scottybinOZ]

I got given a dead subwoofer and found some caps that needed replacing. Got that sorted and the sub works great, except, the transformer hums as soon as power is applied.

The brochure says its a 350W unit and the tx outputs are 2x 41.5 and 2x 17v. I'm not sure if anything useful can be garnered from that info regarding replacement.
Any other options up my sleeve ?

I'm super happy the sub so would be a shame if I can't improve it.
Thank you

 

[zirati]

I have very bad English. Sorry

you have two possibilities:
-That DC is input to the transformer, check the filter and anti-interference capacitors at the alternating current input.
- before changing it, you can try a good bath with epoxy resin to seal it.

Greetings

 

[NareshBrd]

Varnish.
Many threads here.
Check for DC also.
Was it humming earlier?

 

[Bonsai]

Can you make a short recording or video and post it up. The reason I ask is that there are two possible mechanisms here :-


1. Transformer 'growling' which happens when there's DC on the mains
2. Transformer core rattle due to loose laminations.
3. Worst case, a combo of both

The cures for 1 and 2 are different.

For 'growling' it will usually come and go as the DC on the mains varies throughout the day. For loose laminations, it is pretty much constant.

 

[scottybinOZ]

Will do a video but it's pretty consistent sound.
Not sure if it's meaningful or not but a specan app on my phone shows a 150hz peak with harmonics every 50.

I'm not sure how it was before I replaced the caps. The original owner had replaced it with a new sub and said it's not working when they gave it to me.

 

[scottybinOZ]

Thanks for the input on this.
Here's a recording of it on YouTube.
Subwoofer hum