[Amps] Re: Wierd Problem with Alpha 76PA

[WX5L]

 Hello to the Amp group,

 I have an mid 1980's Alpha 76PA amp which is working normal in the transmit
 mode.

 The problem arises in the receive mode  where I have noticed 2 to 3 S-unit
 loss in receive signal. after unkeying the amp.

 I am using a signal generator to produce a solid signal for testing.

 I can push the SSB/CW switch into the OUT position and the signal
 immediately returns to normal. I then push the SSB switch IN and just tap
 the PTT switch of my microphone and notice the loss of signal on the
 S-Meter. I can continue tapping the PTT switch of the mic and signal will
 return to normal after several attempts.

 My transceiver is a Yaesu FT-1000MP Mark V which has always been consistent
 barefoot or with amp off. As a test I pulled out my second rig an Icom
 IC-751A. The results were identical. Therefore the trouble is not with the
 transceiver. I checked all coax connections and are OK.

 The first thing I checked was the TX/RX relay K-4. Of course when the amp 
is
 off the TX/RX is by-passing RF through K4 back out. As said before that has
 never been a problem. Only after I key-up energizing K4 to transmit then
back to RX does the problem surface. While I had it opened up I burnished
 and thoroughly cleaned K-4 but had no effect. I also burnished and cleaned
 K-3 relay which is the plate voltage relay selecting SSB or CW. The reason 
I
 cleaned K-3 was while in the diminished signal I can pop out the SSB button
 to OUT and signal returns. Cleaning K-3 had no effect.

 I would appreciate any comments or advice about this problem. What's really
 confusing me is that in the receive mode K-4 should just be looping the
 receive signal back out to the transceiver with no other interaction but
 that's not the case. There is some interaction degrading the signal in the
 RX.

 While I was chasing VK0MT on 40 meters the other morning it made the
 difference of copy and no copy for me. After each transmission I kept
 tapping the mike PTT to regain full signal.

 Please HELP!

 Cheers,

 Randy
WX5L

WX5L at charter.net
Thibodaux, Louisiana