[Drake] T-4XB Transmitter problem

[Paul S. Serio]

Recently acquired a Drake R-4A, T-4XB, AC-4/MS-4 combo.
Receiver works for the most part. Nothing on 160 meters but I
figure that's a crystal problem. A little hum but that's most likely
curable with a capacitor change. The transmitter makes power
(125 watts) but only from the transmitter VFO. In the receiver
VFO position nothing. Could be the transceive switch I guess but
it was working recently. The transmitter takes spells at NOT
making power though the plate current still looks and tunes
normally. T/R relay maybe? Any help would be greatly appreciated.
Paul, N5PS