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is it normal for a power supply to buzz? (not through audio)

Posted: Sat Mar 01, 2014 5:56 am
by vuuv
I have a jx3p and an alpha juno 2 that have landed in my lap recetly, and both of them make an electrical buzz/hum when turned on -- not thru the audio outs, but from the power supply, inside the synth. is that normal for gear of this age? or should i be worried about a small explosion?

Re: is it normal for a power supply to buzz? (not through au

Posted: Sat Mar 01, 2014 7:00 am
by rhino
Welcome to the board!

SOME small hum is generaly ok, but check:
1) synths are set for the correct voltage
2) rectifier diodes
3) filter caps - look for leakage
4) on the JX3p, check that the transformer has not pulled loose fron the wooden base plate of the synth.

Re: is it normal for a power supply to buzz? (not through au

Posted: Sat Mar 01, 2014 9:35 am
by vuuv
i'll definitely look at the tranformers -- the jx3p is far less noisy and is otherwise in excellent shape, but the noisy juno 2 is being loaned to me (indefinitely i guess) and has seen better days... broken keys i can fix no problem, but diodes and the rest might be a bit beyond my skills right now :) anything beyond unscrewing things is beyond me!

Re: is it normal for a power supply to buzz? (not through au

Posted: Mon Mar 03, 2014 1:26 am
by Stab Frenzy
It's the AC in the transformer creating a magnetic field that vibrates the steel in the chassis at your AC frequency. It's not a problem.

Re: is it normal for a power supply to buzz? (not through au

Posted: Mon Mar 03, 2014 10:28 am
by Psy_Free
My JX-8P has buzzed like a nest of furious hornets since I got it years ago & hasn't blown up yet, so I wouldn't worry too much.

Re: is it normal for a power supply to buzz? (not through au

Posted: Mon Mar 03, 2014 11:41 pm
by vin14
My juno 106 has done that since i got it in the 90s, though my alpha juno 1 hasn't.

Re: is it normal for a power supply to buzz? (not through au

Posted: Mon Mar 03, 2014 11:55 pm
by pmh
As already mentioned, some transformers are prone to buzzing, which will be at the frequency of the mains.

If this doesn't appear in the audio output then there is nothing to worry about.

You can get rubber mounts for transformers, which can/help to reduce the hum, but it's extra effort for nothing really.

I have had to strip our house alarm down, in the past, as the hum from this used to annoy me at night.

That said, I doubt you sleep with the Juno ........ or do you :mrgreen:

Kind regards,



Phil

Re: is it normal for a power supply to buzz? (not through au

Posted: Tue Mar 04, 2014 12:56 am
by gmeredith
The Yamaha TX81z are renowned for their acoustic transformer buzz. It's not a fault issue - just poor shielding and mounting design. Yanaha actually issued a service bulletin for factory recalls for it. The notes told the service technician to do the following modification:

Image

Altitude from this forum also mentioned it:

http://www.vintagesynth.com/forum/viewt ... 35#p564254

So you could probably apply the similar mod to your transformer.

Cheers, Graham

Re: is it normal for a power supply to buzz? (not through au

Posted: Tue Mar 04, 2014 2:33 am
by vuuv
thanks everyone! i'll just deal with it :)

and pmh, i mean, technically what i have now is the bedroom studio thing happening, so it's all within reach from my bed.....

Re: is it normal for a power supply to buzz? (not through au

Posted: Tue Mar 04, 2014 3:57 am
by Stab Frenzy
vin14 wrote:My juno 106 has done that since i got it in the 90s, though my alpha juno 1 hasn't.
That's cause the Alpha Juno is made from plastic not steel.