8mm Forum: Sankyo 702 humming noise

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Posted by Lee Panton (Member # 4443) on September 17, 2014, 11:21 AM:

When i plug the lead from the projector into the wall socket and switch on without starting to run the machine i hear a humming noise but is this normal for the 702 or does it mean the amplifier or power supply is on its way out. Apparently this machine only had about 10 hours use over a few years but could have been sitting in a box for many years. Only got this machine a few days ago and the seller claims its fine. The machine is running fine otherwise.

Posted by Steve Klare (Member # 12) on September 17, 2014, 12:31 PM:

How bad is the hum? All old audio circuits will have some of it, it's just a question of how tolerable it is.

It could be that the electrolytic capacitors in various filter circuits are dried out and aren't very capacitive anymore.

They dry out with age alone, and go even faster without a voltage being present to keep them formed up. This many years down the road none of them should be working by any usual standard (yet they do...).

They aren't that hard to replace if you are up to it.

Posted by Lee Panton (Member # 4443) on September 17, 2014, 01:23 PM:

Thanks Steve. The hum is not loud or distracting just slight noise…seems to be performing fine though. Just purchased this machine a few days ago…according to the seller it only had about ten hours use over a few years but it could have been sitting unused for many years.

Posted by Steve Klare (Member # 12) on September 17, 2014, 02:36 PM:

Sure,

As long as your soundtracks drown out the hum it's not a problem. When you start to hear it during quiet scenes, then you have an issue to work on.

I actually like just the slightest trace of hum: it lets me know that the sound is all connected up and turned on.

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