[R-390] R-390A Noisy Ant. Trim and Raspy Calibrator

[Roger Ruszkowski]

Ken,
 
E208 is on the grid of V201.
 
The test point is 470K or 33 PF off the cal signal that just happens to be  33 ohms off ground.
That cal tone on the grid of V201 is only about 1 micro volt.
 
Plus you will only see it if you are in the cal mod of operations.
I am not surprised that you do not see any thing on E208 with the scope.

On E209 you would expect to see micro volts of signal from the RF chain.

The double signal you see could be from either the 17 Mhz first crystal oscillator
or the cal tones. What is the difference in signal at E209 when you are in MGC and CAL.
considering you are switching the cal tones off or on?

I think you are just seeing the first crystal oscillator signal on the grid of V202 at E209
and it looks like nothing as it is being capacitor coupled through a couple different paths
with the 6C4 tube and circuits.

These are tough problems to trouble shoot. The signal levels are just to low for most of our scopes.
And at these low levels there is so much crud about that has no real meaning to the circuit performance.

Go for clean and deoxit.

Get out the little wrench and Philips screw driver. Open every ground lug bolt and clean the connection.
More than one problem has been a 50 plus year old oxide layer in a mechanical connection on a lug.
 
 Roger AI4NI