[Kenwood] TS-440S issue

[Howard Holden]

Got a TS-440S which has suddenly acted up on transmit – not the dot problem. This is a later issue radio.

Seems like I’m getting RF feedback into the rig, regardless of which antenna I use, even a dummy load. Problem is particularly acute on 40M but present on 80 thru 17M as far as I’ve checked. Depending on the antenna, I can get only 20 to about 50W out before there’s a buzz on the signal, and increasing power beyond that makes the display blink on and off rapidly and irregularly. 

I find nothing loose internally, I removed and reseated the connectors on the pot control boards thinking there might be a drive pot issue. I’ve relocated all antenna lead-ins and checked the tightness of all connections. Put the keying lead a number of turns on a toroid (T-240-43, which works great for TVI), got choke baluns on antenna lead-ins. 

Any good ideas out there, anyone with a similar problem?

Thanks

Howie WB2AWQ/7