[SignalOne] Who works on CX7s?

[David Bertman]

Hi --

     Well, I'm not guaranteeing anything, but it sure sounds like this is
the problem.
It is not too hard to change, but requires some patience.

     First, to diagnose the problem you need to check the 34v power supply.
This
should be pin 132 or 131 of your power supply (I have only worked on old
ps, but from
schematic this is same on "B" ps).  If regulator is out the level will be
over 40v (normally
about 37v with no load).  If this is the problem, the 34 v regulation is
out and you need
to replace the pass transistor q4 mounted on rear of chassis.  The other
transistors which
determine its bias  could be gone too -- these are all on the ps board.
All can be
replaced without pulling pins on ps board (and I have replaced all!).  The
problem could
also be in other regulators.  On "B" ps these are three terminal devices,
and are also
mounted on chassis rear.

     Best way to check for hum from this type of source is with a scope.
You will
see quite a dramatice angular form when regulation is out.

     Hope this helps.

     Dave AB7B