Transformer hum fixed

[bobinaz]

I've had a Mitsubishi tuner preamp DA-C7 for years but never played it much due to an annoying hum whenever it was plugged in. No inputs, no connections, with / without ground and it had this hum. No speakers hooked up. I suspected the main transformer, tightened the screws to the chassis, no help. So I tried unscrewing the transformer from the chassis and just let it sit on some rubber tubing....no more hum. So I secured the transformer to the chassis using rubber washers between the transformer and the chassis. Still no more hum. The transformer itself was still grounded to the chassis. Maybe something to try on other units. I included pics on the transformer.

 

[sKiZo]

Good catch - a lot of what some call hum is mostly mechanical vibration. I did the same with a custom tube amp when mounting the iron to the chassis. I also have an Eico that I was able to quiet down by beefing up the clamps holding the multi-cap.

 

[Blue Shadow]

The make isolation mounts, threaded on each end with rubber in the middle. Have em in a twice power block, a large transformer designed for power conditioning. The transformer weighs so much it shears the mounts when the unit is shipped. McMasterCarr has all kinds of isolation mounts for those that find a need.

I've been watching the transformer revarnishing thread as I have some gear with transformers getting a bit noisier. Glad you got you unit quieted down.