Both of you have the advantage of having a 5214, I don't!
Though, Amie's post #4 says the octal valveholders are riveted in, which sounds like a factory job from Day 1, not a retrofit by Smithy the Serviceman.
What would clinch it, is the holes in the chassis. P valveholders need big holes; Octals smaller at 1 1/8" holes. If the holes are correct for octals, then it has always been thus right from punching the chassis. If adaptor plates are fitted, then it could have been either.
Whatever the situation, 95pF is clearly too high and it needed replacing. And, personally, I'd connect the 20pF capacitor right across the gang (or its parallel trimmer), keeping fingers firmly crossed that the original designer hadn't compensated for a non-ideal connection point by fudging the L and C values!
The Trader sheet, like the circuit snippet that Mike put up in Post #8, doesn't help this discussion by leaving pin numbers off the diagram
(even if two sets, for P8 and IO are necessary).
Breaking into oscillation except when a strong signal is being received... I'd suggest that instability is mild, and a strong station generates enough AVC voltage to bias the valves to a low gain which doesn't oscillate.
All makes for an interesting, ongoing repair
Mike Watterson Wrote:I'd say the octal conversion was slightly amiss.
Though, Amie's post #4 says the octal valveholders are riveted in, which sounds like a factory job from Day 1, not a retrofit by Smithy the Serviceman.
What would clinch it, is the holes in the chassis. P valveholders need big holes; Octals smaller at 1 1/8" holes. If the holes are correct for octals, then it has always been thus right from punching the chassis. If adaptor plates are fitted, then it could have been either.
Whatever the situation, 95pF is clearly too high and it needed replacing. And, personally, I'd connect the 20pF capacitor right across the gang (or its parallel trimmer), keeping fingers firmly crossed that the original designer hadn't compensated for a non-ideal connection point by fudging the L and C values!
The Trader sheet, like the circuit snippet that Mike put up in Post #8, doesn't help this discussion by leaving pin numbers off the diagram
(even if two sets, for P8 and IO are necessary).Breaking into oscillation except when a strong signal is being received... I'd suggest that instability is mild, and a strong station generates enough AVC voltage to bias the valves to a low gain which doesn't oscillate.
All makes for an interesting, ongoing repair
