[R-390] IF module ---

[Pete Williams]

G'day list..... thanks to the respondents on the 1st Osc problem... fixed
that with replacement of  capacitor C327 across T 207.
Now....new problem... alining the IF module per book and no connection to
the RF module , I find that with the cover off the filters  and no tube
covers on adjacent tubes , the IF module bursts into oscillation when
adjusting the 4 kHz trimmer--- but only the 4 kHz trimmer at top. All other
filter adjustments / trimmers OK. , put the filter cover on and a couple of
tube shields makes things normal--- but it shouldn't happen.
Reducing the IF GAIN pot tends to minimize the problem and amplitude of the
oscillation as shown on the diode load voltage 
Maybe there is a contributing factor in the fact that the AGC voltage is
less with the 150uV input than what one might expect- hence excessive gain.
Comments and advice on further directions  appreciated.
A proper dog this one !
 Cheers
Pete VK3IZ