CFD-V17 Hums/Buzzes

[s.w]

I have a sony cfd-v17 which has been in my possession for about 10 years but ever since i got it it has emitted a buzz/hum when it is off

I have been told it could be the power supply but not really sure what to do about fixing it.

anyone had this problem or know what to do about repairs?

Despite this the unit sounds pretty good and everything else works. it has an excellent radio.

Thanks

 

[Superduper]

If the hum is not present when it's on, it might not be the power supply. Of course it might be hard to tell since with music playing, the hum would be hard to detect unless it's set to a quiet function. The thinking is that any power line induced hum from poor filter capacitors will be present all the time -- not only when the machine is off.

The thing is, when it's off, the amp should be off too. Most modern amp IC's have a high impedance mute / remote turn on circuit. This allows the amp to be hooked up to the power rails all the time but be switched on/off by a low level signal from the MPU. If that circuit has failed, then the amp could be on all the time.

So it could be:
Bad filter capacitors
Ground loop issues (check for poor ground connections and cold solder joints).
Bad amp module not turning off when it's muted.
Bad MPU that is not properly switching off the amp module.
Problem in the circuitry between the MPU and Amp chip.

The first item I would look at is #2 -- ground loop issues. Bad news is that for the non-technical minded, none of these fixes is an easy DIY'er.

 

[s.w]

the hum is present whether it is on or off depending on the music you can hear it.

It actually does not come from the speakers but somewhere inside the boombox

 

[Superduper]

Transformer. Try to secure it better, make sure none of the shielding is loose, and perhaps adding self stick urethane foam insulation tape to try to dampen it. If that doesn't work, then there's nothing you can do short of replacing it because the laminated core could be delaminating. Transformer cores are made of metal plates laminated together. By nature, a magnetic field is reversed 60 times per second. This can cause vibration that results in a hum.

 

[s.w]

Thanks