The AM Forum

I'd like to get some feedback from the forum on this one.  I have a 6 meter receiver that is behaving in a odd manner.  I don't recall running across this kind of problem before.  The receiver is a 6M Gonset, Comm 3 variety (3136 I believe).

What is going on is this RX does not quiet (receiver noise) with a signal of even moderate strength.  It will quiet at about 50 uvolts, but it should begin to quiet after perhaps 5 uvolts.  Here are some observations:
The IF strip RF looks very similar to others of the same model.  P-P levels seem typical.
The AVC works normally (typical voltages)
I tested the IF/RF tubes, all read good on a quality Weston tester (no leakages).
I also tried swapping out the detector and clipper tubes (6AV6 and 6AL5)
The voltages around the detector and squelch circuit are normal
Voltages on the IF strip are all normal (6BA6s)
The RX meter signal strength is typical for these receivers

It seems like a bad cap somewhere in the front end, but I'm not certain of a reasonable method to isolate this if this is it at all.

TNX
Peter
n1ps

If I had to start somewhere, I would first pull the 2E26 just to make sure the hash/noise wasn't coming from the transmitter side. If noise is still there, then I would pull the 6BZ8 RF Amplifier. Is the noise still there? If it's there, then it it's possibly in the IF string. If noise has been substantially reduced when pulling the tube, then re-insert the tube and check the voltages on all the pins. Check the resistor values in this area. If voltages and resistor values are per spec, I might try another 6BZ8, to see if it made any difference. A scope works wonders for this type of problem. You might also check and/or replace the OB2 to make sure it hasn't become a noise generator. It supplies regulated B+ to the oscillator and the detector.

I meant to post a response to Pete's (wa2cwa) suggestions.  The RF amp was indeed the culprit.  I replaced several components around the amp and that solved it.  The DC voltages were all goofed up...not sure how I missed that one. 

TNX

Pete
n1ps