[R-390] IF Deck Revisited (Revisited)

[Flowertime01 at wmconnect.com]

Barry,

You wrote that the problem persisted in the IF deck as you injected 455 into 
the plate of the third mixer. You can leave the RF deck aside for a bit. 

Next do a wire harness check on the RF gain and from the rear panel to the IF 
deck.

Lay the receiver on end and swing the IF deck out. Do the harness 
measurements from some where out side into some where inside the IF deck to ensure you 
are not going through a bad pin in the IF deck connector.

Check the receiver in all the KC bandwidths on the IF deck. A likely problem 
is in a mechanical filter circuit and AGC circuit at the mechanical filters. A 
couple of the bandwidth switches get the filters and AGC circuit combined. 

An open in the AGC line will get you. In MGC there is a big resistor to 
ground in the IF deck. It is good enough to give you MGC operation even with the 
jumper on the back terminal board open. Check that jumper for a loose screw. 
When you go over to AGC you expect a negative voltage on the AGC line instead of 
ground. IF the AGC is open then you get a more positive grid voltage instead 
of a negative grid voltage. So you get more gain in AGC than in MGC while we 
expect less gain.

Roger. AI4NI