[Hallicrafters] help with SR -150

[K4PRF Burton Pratt]

I have owned this transceiver since it was new and put it aside several 
years ago because of a problem that I haven't been able to correct.  The 
receiver is as good as it ever was but I cannot get more that a few 
watts out in either USB, LSB or CW with the transceiver set up for 
normal SSB operation  I have checked all of the usual bias points and 
they look good.  The SR-150 will make good power only if I un-balance 
the carrier which puts the rig into a DSB mode.  Voltages on all the 
tubes are  close. Considering the fact that the output increases as the 
carrier balance controls are d-tuned leads  me to suspect a problem in 
the balanced modulator circuit.  If I am on the right track I have 
somehow been unable to isolate the culprit.  Any suggestions will be 
appreciated.

Burt Pratt, K4PRF