AC dimmer module causing transformer buzz

[John_MS]

I have a microscope for repair with a 6V 30W transformer (powering a halogen lamp).

The dimming is done by a module on the primary (mains) side consisting of a plastic 250K potentiometer, a few resistors, capacitors and a BTA08 600C Triac (photo to be attached if i can).. Triac is on the underside of the board.

At low power the transformer buzzes loudly. I initially thought this was a transformer problem but switched it with a known good and the problem persists.

I have briefly inspected the dimming module and can't see any obvious problems (cracked joints, burnt components, etc).

Could anyone point me in the direction what the problem could be? Triac?

Alternatively, does anyone know of an off-the-shelf replacement module which would do the same job?

Thanks in advance.

Kind regards,

John

[PKTKS]

DIMMERS are pretty simple to the letter.

BUZ kinda spark somewhere...
 POTENTIOMETER? CAPS? or else...

pretty much you de-solder  check replace them
as is..

just in case some "TRIACS" also incorporates the DIAC
some even ditch them to be cheap... incorporated DIACs
are hard to find. Nevertheless you can replace them with
a pair DIAC+ TRIAC just fine

Paul

[John_MS]

Thank you Paul.

Yes, I will desolder the components and test individually.

It looks like that model of TRIAC is still available should I need one.

Kind regards,

John

[themadhippy]

Nothing unusual in a tranny buzzing with a dimmer.For silent operation move the dimmer onto the secondary side

[John_MS]

Thanks. The buzzing is very loud and not present on the other microscopes.

However, yes I think this is a poor design with the dimmer on the mains side.

Actually, I'm tempted to remove the entire workings and replace it with an LED as I've done in the past.

It will be an interesting exercise to see if I an find the fault on this anyway.

Kind regards,

John