[Kantronics] KPC-3 CALibrate mode

[Joe]

I just repaired a KPC-3 that had a damaged PTT Mosfet.
 It now keys the radio (used to be stuck in transmit)
but now the Calibrate mode is not working properly. 
When I put it into the calibrate mode, it will only
key for a fraction of a second using the M,S or T
command.  Aside from that, it appears to be working
fine.

Any ideas?

73, Joe, K1ike