SERVICE NOTE 013A
LOW OUTPUT AND OR SUDDEN FREQUENCY SHIFT:
This is usually and intermittent problem but affects 1 in 15 radios. The coil in the VFO is 29 turns of 32 AWG green solderable 155C wire tapped at 25 ¾ turns. The tap is constructed by laying a small square of fiberglass toroid tape over the winding as you pass the 25th turn mark and laying the 25 ¾ turn over the tape followed by the remaining 3 turns under the tape. They simply wrapped a #32 wire under the 25 ¾th turn and soldered it: the coating on the coil wire burns off at 155C. A fairly good test of the solder joint is to wiggle the 12BA6 while looking at the VFO output. If it changes, clean the tube socket with a between tooth brush and DEoxit and if it still fails, power it off and use an ohm meter connected from either end to the tap and wiggle the tube. If it varies rewind the coil.
Rewinding the coil is not difficult. Simply wind using two wires to achieve the correct spacing and remove one when finished. NOTE: Use solderable #32 wire so you won't have to strip the varnish to solder it.