Rotel RC-1090 preamp Humming

[bigAl]

I have a rotel RC-1090 preamp that hums by just being plugged in, nothing is connected to it, whether it's on or off it still has a moderate hum. has anyone came across this problem and was done to fix it. Thanks

[madmac]

It hum's even when it's off??!!!. That's VERY odd??!!. I am assuming it works fine otherwise?.

[Kevin D]

For clarification, the transformer inside the unit is humming correct? No speakers or amp hoked up?

If so, we've seen it before with not so great power. Might need to try another outlet or get a conditioner.

Kevin D.

[Glen B]

DC offset of as little as a couple hundred mVDC on the AC mains can cause transformers to hum or buzz, but that is more prevalent with larger size transformers like those in amplifiers, versus the smaller sizes found in preamps and source components. I would check the home for possible sources of DC (ceiling fan speed contols, heating temperature controls of any kind, light dimmers, halogen lights, etc.). These devices often employ diodes or silicon controlled rectifiers (SCRs or thyristors), which draw current only on 1/2 of the AC sinewave, creating the DC offset. If that is not the problem, the transformer could have a loose mounting bolt or loose lamination(s). The RC-1090, once plugged in, is fully powered up and only in standby. The "on/off" switch only mutes/unmutes the output.

[bigAl]

Rotel RC1090

It hum's even when it's off??!!!. That's VERY odd??!!. I am assuming it works fine otherwise?.

When it's on there's a moderate hum when I turn it off the hum sounds a little lower, When I connect a source to it it sounds beautiful. no hum through the speakers.

[bigAl]

Yes your correct on both your questions, and I did bring it in other rooms in my house plugged it in same problem.

[bigAl]

Thanks very much to everyone trying to help. BigAl