[Kenwood] TL922A noise

[Bill Riches]

I am using a TL922 an Icom 7600 and I am keying the amp via a keying relay.
A noise problem just showed up.  When amp is keyed or unkeyed a loud pop is
heard in the receiver.  It hits 20/9 on the s meter.  Amp is working ok -
1kw with 100 watts input. Idle current is 175 ma. 

 

I disconnected the transceiver from the amp and hooked up the Tek 465 so see
what is coming from the amp input to the 7600.  I see 6 volts ac when keyed
and I also see a 75 volt pulse when the amp is keyed and then it is unkeyed.
I haven't taken the bottom off of the unit to check out bias relay and the
bias diode D2 and the 100 mf cap C26 across the diode.  I am going to check
that out tomorrow.  The amp was bought new in 1986 with the same finals and
no problems.  When I purchased the amp I put an hour meter on it and only
have about 1000 hours on the tubes. I don't want to use the amp until this
problem is resolved as the 7600 does not like strange pulses coming back at
it!

 

Any ideas on what this problem could be?

 

73,

 

Bill, WA2DVU

Cape May, NJ