I have a buzzing mains transformer on a SE amplifier. It's an old transformer. I've read up on some things to do like re-gluing laminations, dipping it in shellac and methylated spirits etc. But are there some simpler things that will lessen the buzz? For instance:
- Mount it on rubber feet
- Insert bolts into any unused holes and bolt the laminations tighter?
- ??? anything else
The transformer is a good size and doesn't get hot, so though there's no markings to identify it, it shouldn't be stressed.
- Mount it on rubber feet
- Insert bolts into any unused holes and bolt the laminations tighter?
- ??? anything else
The transformer is a good size and doesn't get hot, so though there's no markings to identify it, it shouldn't be stressed.
1) You can make a cover for it and line it with Dynamat. Since you said it doesn't get hot the cover shouldn't cause heat issues.
2) You can decrease your line voltage with a variac or AC regenerator/regulator. Lower line voltage usually means less buzz.
3) You can removed it and have it vacuum impregnated at a transformer or electric motor repair shop.
2) You can decrease your line voltage with a variac or AC regenerator/regulator. Lower line voltage usually means less buzz.
3) You can removed it and have it vacuum impregnated at a transformer or electric motor repair shop.
I'm first of all looking to see if there is a quicker fix. I inserted 4 extra bolts and tightened them up, but this achieved nothing. Next, try out rubber feet.
I just watched a video where the builder used a piece of dual sided copper PCB board sandwiched between the transformer and some short rubber feet. They grounded the copper PCB to the star ground. Reportedly worked on a noisy Edcor PT.
300B DIY Budget Tube Amplifier Build DHT SET - YouTube
300B DIY Budget Tube Amplifier Build DHT SET - YouTube
Andy,
Does the transformer have an end bell(s)? Try removing it/them.
Does it buzz with no load? Can you feel the core buzzing?
Yes rubber mount is okay. Soft grommets work if you can enlarge the mounting holes and felt pads also work as long as you do not over compress them. Either case, make sure you ground the transformer frame back to the chassis.
Does the transformer have an end bell(s)? Try removing it/them.
Does it buzz with no load? Can you feel the core buzzing?
Yes rubber mount is okay. Soft grommets work if you can enlarge the mounting holes and felt pads also work as long as you do not over compress them. Either case, make sure you ground the transformer frame back to the chassis.
Soak it in motor insulating varnish, preferably on load.
Or brush it on....again preferably on load.
Here it costs 50p (UK) for 200 ml. More than enough.
Ask for Class F, failing which class B varnish.
Glug humm hmm silence.
Or brush it on....again preferably on load.
Here it costs 50p (UK) for 200 ml. More than enough.
Ask for Class F, failing which class B varnish.
Glug humm hmm silence.
Try to find a transformer manufacturer who will vacuum impregnate and heavy varnish dip it for you. Watford Control Instruments for whom I used to work might be worth a try.
No end bells. Doesn't buzz with no load sitting on the bench.
On load I feel some very faint vibrations, but not anything substantial.
I have another identical transformer, but with end bells. I'm about to try that out. If that works I have a working PSU and I can do experiments on the buzzing one later, incorporating all the ideas in this thread.
The buzz is caused by hysteresis making something loose vibrate.
Can be an air gap in the laminations, dried out potting compound, whatever.
I simply run them on load, and varnish the coils and laminations.
On load means it is warm to hot, so the varnish flows better, and the vibration makes it find its way to the right place.
If possible. loosen slightly the bolts holding it together, tighten after the varnish has gone in.
Varnish takes a long time to set, and has a long pot life compared to other potting compounds, will not dry up if left open for an hour or two.
Just soak it in varnish, connect on load, for about ten minutes.
Take it out, let it dry overnight in a well ventilated area.
The excess varnish can be stored after adding a little (compatible) thinner.
Vacuum impregnating again to an existing unit...no experience.
Can be an air gap in the laminations, dried out potting compound, whatever.
I simply run them on load, and varnish the coils and laminations.
On load means it is warm to hot, so the varnish flows better, and the vibration makes it find its way to the right place.
If possible. loosen slightly the bolts holding it together, tighten after the varnish has gone in.
Varnish takes a long time to set, and has a long pot life compared to other potting compounds, will not dry up if left open for an hour or two.
Just soak it in varnish, connect on load, for about ten minutes.
Take it out, let it dry overnight in a well ventilated area.
The excess varnish can be stored after adding a little (compatible) thinner.
Vacuum impregnating again to an existing unit...no experience.
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Quite likely. I'm going to try it out in an ABS box with diode rectification. With and without rubber feet. No metal to resonate.