[sdiy] Xpander PSU problem (¿PSU rev 2.0?)

Sergio Villar Koval kovalmoog at hotmail.com
Mon Nov 3 16:51:05 CET 2008

Hi to the list...

I have a very big trouble with an Oberheim Xpander.
Its power supply are dead and it has a different design
than that PSU found on the well known Xpander service 
manual on internet.

That PSU has only two transformers, one to reduce input
AC and another with multiple AC outputs, and the PWM chip 
is the U5561. 

Mine's has three transformers, there are one of them in 
a middle stage that increase the AC several times, so
the third one (with multiple outputs, too) takes its input 
from a very higher voltage than the first design one.
Its PWM controller chip is the MB3957.

¿Has anyone some technical info about that second PSU?

The trouble is around the second transformer, the PCB 
was broken and its outputs was cutted from inside the coil.
There are no chance in to restore it.

If anyone has some info about that transformer (mainly
its transforming rate) it is maybe the only info that I need.

Thanks in advance.
Best regards


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