> yes , actually 5 minutes after posting the previous post the
> a-126 was dead again, and today it works again, better than not
> working at all.

Totally strange. But I have one last idea. We discovered that the internal
quadrature VCO of some A-126 does not start now and then if the
corresponding control is in the fully CCM position during power on (i.e.
lowest shifting frequency ~ 50Hz). But it should start as soon as the
frequency control is turned clockwise. We believe that it has to do with the
power on details, i.e. how fast and in which sequence the +12V and -12V turn
on which in turn has to do which power supply is used and which modules are
installed. In any case the VCO does not start if the frequency is less than
~ 50Hz (e.g. if the frequency offset trimming potentiometer has been changed
by the customer to obtain a lower shifting frequency than 50 Hz).

Best wishes
Dieter Doepfer