Vintage Synth Repair

Hi Frank

 

All transformers hum to a greater or lesser degree when powered up.  This
may be a loose lamination rattling or it may be a less than perfect gap
creating what is known as magnetostriction; this is an oscillation of the
air across the gap.

 

On audio equipment it is normal for a manufacturer to minimise all such
noises, nevertheless some noise will remain.

 

Regards

Brian G3OYU

 

From: vintagesynthrepair@yahoogroups.com
[mailto:vintagesynthrepair@yahoogroups.com] On Behalf Of Frank Simon
Sent: 30 June 2010 4:31
To: vintagesynthrepair@yahoogroups.com; SequentialCircuits@yahoogroups.com
Subject: [vintagesynthrepair] Re: Prophet 10

 

  

Are there any Prophet 10 owners that can answer a question for me? Can you
hear your transformer hum when you power up?

Frank

----- Original Message ----- 

From: Frank Simon <mailto:FSIMON001@...>  

To: vintagesynthrepair@yahoogroups.com ; SequentialCircuits@yahoogroups.com 

Sent: Monday, June 28, 2010 11:24 PM

Subject: Prophet 10

 

My P10 is wacko. Sometimes I turn it on it lights up and acts like it wants
to work but if I cycle the power nothing will light except the tune LED as
if it is in tune mode but doesn't time out. If I cycle power something
different may happen. I think the PCB3 board has issues would anyone agree?
All Power supplies are good with DVM but I see noise ripple on supplies with
.2 to .5V that seems high to me. It is not 60 cycle ripple but very random
noisy ripple. Not sure of best trouble shooting approach of this board. My
P10 shematic is freeby with poor zoom in ability. My P5 is better but
refernce designators and power supplies seem different. Anybody got a good
service manual or advice?

Frank