[R-390] Below 8mhz problem

[David Wise]

> As an update, I have found that E209, before the 1st mixer 
> has low voltage.
> It should be approx -6.5 volts, and it actually is -.85.  
> Measured with a
> 1meg resistor it is -.76.

[list of suggestions snipped]

I don't quite hear you saying you checked the 1st oscillator
itself.  Make sure you do; without it, you won't get anything
below 8, no matter what shape the 1st VIF is in.  I don't
remember the canonical method to check it but an easy way
is to pull the 1st mixer and scope the cathode pin.  This is
where the 1st oscillator is injected.  Should be a big,
clean 17MHz sine wave, quite a few volts high (memory fade... 10?).
NOTE that the 1st oscillator only runs when you're below 8.
The E209 check measures this voltage in a way.  When you put
a voltmeter on E209, it sees the mixer grid and it looks like
the plate of a diode.  Every time the cathode swings negative,
the grid conducts and takes the meter with it.  This happens
17 million times a second; the meter averages it out.

Regards,
Dave Wise