[Motorola] Service monitor

[Glen Zook]

I have a Singer / Gertsch FM10C service monitor that
has ceased to work.  The synthesizer seems to be the
problem.

Now I do have the full service manual on the unit and
can "trouble-shoot" if necessary.  However, I am
seeing if anyone has had a similar problem before
getting really involved.

The reference oscillator (Motorola TCXO at 10.0000
MHz) is working fine.  Also, the internal tone
generator is working but is about 42 Hz low in
frequency (should be 1000 Hz but is 958 Hz when
measured on a frequency counter).  I did find several
25 volt electrolytic capacitors in the power supply
that were leaky and replaced them with 35 volt
capacitors.  Also, I have checked the various
connectors including cleaning those on the 3 plug in
units and have cleaned all of the switches and
potentiometers.  The regulated 9.0 volt adjustable
voltages (there are 2 of them) have been set
correctly.

I have tried unplugging the deviation oscilloscope to
see if it is "loading" the circuit.  That does not
have any effect.  The "trace" on the oscilloscope is
not working correctly.  It can only be adjusted to
about 1/3 the width of the screen and it goes to
either one side of center or the other.  The "pip"
stays in the center and then the trace can be adjusted
to one side or the other.  Also, the trace cannot be
adjusted the full vertical range.  It starts at the
center and can be adjusted upwards.  However, it
cannot be adjusted to the lower half of the screen.

Anyway, all of the problems happened at the same time.
 The operation was intermittent for a few days and
then the unit quit working.

I do have a Motorola service monitor that I am using. 
However, the Singer / Gertsch is my "back up" and I
definitely need to get it going again.

Glen, K9STH

Website:  http://k9sth.com

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