UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Trio Lafayette KT-320 Question

Skywave · 23rd Nov 2019, 2:17 pm

"BFO coil losing Q": yes, a possibility, but note that Jerry (the OP) did state in post 16 that when he adjusted the core of the BFO coil, the tuning was very sharp. That suggests to me that the LC circuit that constitutes the heart of the oscillator is O.K.; hence the coil is O.K.

OTOH, Jerry did state that he tested the valve: a 6AV6 and also tried a replacement. In the past, when tackling similar faults in other comms. radios - "Is this valve faulty?" - I have found more that two replacement valves failed to fix the problem - it wasn't until a third (or possible a fourth) valve was fitted that the problem was fixed. Having said that, though, those valves were not new ones.
Consequently, I don't think that here we have unquestionably eliminated a faulty 6AV6 valve as being the culprit.

Hence, one Q. remains. Jerry: you stated that you "tested the 6AV6 valve(s) and they were O.K". What did you use to make that assessment?

Al.

23rd Nov 2019, 2:17 pm	#25
Skywave Rest in Peace Join Date: Jun 2006 Location: Chard, South Somerset, UK. Posts: 7,457	Re: Trio Lafayette KT-320 Question "BFO coil losing Q": yes, a possibility, but note that Jerry (the OP) did state in post 16 that when he adjusted the core of the BFO coil, the tuning was very sharp. That suggests to me that the LC circuit that constitutes the heart of the oscillator is O.K.; hence the coil is O.K. OTOH, Jerry did state that he tested the valve: a 6AV6 and also tried a replacement. In the past, when tackling similar faults in other comms. radios - "Is this valve faulty?" - I have found more that two replacement valves failed to fix the problem - it wasn't until a third (or possible a fourth) valve was fitted that the problem was fixed. Having said that, though, those valves were not new ones. Consequently, I don't think that here we have unquestionably eliminated a faulty 6AV6 valve as being the culprit. Hence, one Q. remains. Jerry: you stated that you "tested the 6AV6 valve(s) and they were O.K". What did you use to make that assessment? Al.