{Collins} KWM2 RF/AF gain issue



So now that the KWM2 is on the desk, I am running it through it’s paces.
To my knowledge no local expert so I am pushing on with the group.
Transmit seems perfect and great audio so I am leaving that alone for now.

I am hearing a crackle in the receive audio chain and it is very evident when the AF gain is turned lower then 9:00.
It is still there when it is at 7:00 and more pronounced when the RF gain is at 5:00.  So at AF 7:00 and RF at 5:00 is cracking the most.

Might be more RF gain related as when I turn the RF gain to 3:00 the cracking noise goes away.

A different test with the calibrator on and AF gain at 7:00 or off, the receiver provides a distorted signal  (when I am expecting nothing at all in the speaker) but when I advance the RF gain to 3:00 that noise goes away.  It is more distorted than cracking.  When I advance the AF gain beyond the 9:00 position the distortion goes away and sounds like a sine wave.  Have not taken a scope to it yet but it sounds pretty clean to me.


All tubes show good with my checker.  
I ordered the capacitor kit for the KWM2 and as this radio is circa 1964 I figured I have nothing to lose on that. I believe it is about 6 caps and one can.   Assume the can will take me to my limit but seems others have done that before me.

Any thoughts on anything else that I should be looking for?

de KG9H





This archive was generated by a fusion of Pipermail (Mailman edition) and MHonArc.