1954 Philco high b+ issue.....

[jr_tech]

*Really* off the wall, but what if the IF amp was oscillating? This oscillation might stop and cause voltages to change when the circuit is probed. Perhaps the FM reception could be explained, as well by the IF acting as a crude local oscillator/mixer circuit.

jr

edit add: the split chassis Philco sets early to mid 50s were pretty solid performers.