[TenTec] Omni VI Plus Question

[BPCI at aol.com]

I just bought a used Omni VI Plus. It sounds fantastic, but won't transmit.  
In "Tune" it turns off the receiver, but does not put out any power. Using the 
 keyer also turns off the receiver, but doesn't transmit any power. And using 
a  key does nothing (ie does not turn off the receiver). There is no meter  
indication during any of this. Can anyone suggest what is wrong? The seller  
assures me it was transmitting when it left him. Thanks, and 73, Ci
 
Ci Jones,  WU7R
FISTS #10789, CC #1853
NAQCC #306
ARCI #12163
SKCC  #22