[R-390] R 390A Work in Progress (Long)

[Flowertime01 at wmconnect.com]

Bill  KB9IV,

 I seems to receive well
however but overloads on moderate to strong signals......yes the AGC jumper is
on the rear.  Reducing the RF gain corrects this overload,, all tubes tested 
fine.

Check the tube types once more to make sure you do not have a wrong type 
plugged in some where. There are a lot of substitutes that work or almost work 
accept for some side effects that vary with tube type and socket inserted into. 
We do not know all the wrong possibilities.


Most likely you still have a bad cap some where. As reducing the gain helps, 
the clue is that large signal voltages get distorted.  As you check caps 
solder joints and out of range resistors, there are some better values that can be 
used in the replacement process for the caps. Read the pearls of wisdom for 
the specific caps that when replaced provide better audio fidelity.

Some tube plate resistors go bad. A tube gets run to the point of almost 
smoking a plate cap and then gives up and dies. The tube gets replaced when it 
died, the receiver returns to operation and no one looked at the toasted plate 
cap. Hay on visual they look OK. They are not chard. 

You will just need to do some real time trouble shooting.

Divide and localize. Into the If deck with 455 and audio looking for that  -7 
volts on the diode load, the 1/2 watt out of the local on the back panel and 
that 30: 1 signal to noise difference.

If you have not got that in the IF and audio deck you know there is a problem 
in those decks and no amount of work on the Rf end will mask that IF and 
audio problems.

Good luck, You can fix it. It just will take yo some time.

Enjoy your self along the way.


Roger AI4NI

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