[Amps] ALPHA 76PA problem

[DGB]

I'm having a problem that once I key/unkey the amp, rcv don't come back. 
If I push the cw/ssb/or Out=Stby, rcv comes back. Happens on all 
bands/modes. It worked okay before vacation but after two months sitting 
idle in a cold shack this started occurring.

What is most likely causing this? First thought was a dirty relay but 
this amp has had the Byrd mods done to it long time ago so the open 
relay no longer exists.

TIA 73 Dwight NS9I