[Heathkit] SB-401 SB-303 No Receive

[OTAKEBI at aol.com]

I have an SB-401 SB-303 combo.
A a few days ago during an SSB rag chew the rig did not go back to  receive.
After two or three taps on the push to talk all went back to normal.
However, tonight it is dead on receive.
Transmitter puts out full power and if I plug in a speaker direct to the  
receiver I hear fine again.
I have been having an intermittent problem with the relay on the  transmitter.
Sometimes I would get power out and sometimes not.
I took the radio and opened it up removed and cleaned the relay and for the  
first time since owning the radio I have had no problems with intermittent 
power  output or fluctuating grid current but now this.
Should I check for a bad tube in transmitter or am I going to have to take  
that relay off the bulkhead again.
Any help to get this old beast working would be great.
Thanks in advance,
Dan/N4VET