Hi All!!
I had a question about the IF transformers in the AA5 tube type AM radio chassis. Is there a way to tell if the IF transformers are series or parallel circuits? I think that because they are tuned circuits (tank circuits) that they must be parallel circuits? Any ideas on this subject? Also one other question, can I tell by looking at the schematic diagram if they are series or parallel? Thanks so much for any input on this subject!!
Thank you kindly!!
Daniel Rine

Hi Daniel,
Easy. All are parallel circuits, both transformers and both primary and secondary.
The primary of each transformer provides a DC path through its windings to the plate of the tube at its input. In octal terms that is the 12SA7 for the input transformer and 12SK7 for the output transformer. The secondaries are in the grid circuits of the down stream stages. In octal terms that is the 12SK7 for the input transformer and 12SQ7 for the output transformer.
Each present the maximum impedance at the IF. This provides the maximum voltage to the tubes, which are voltage amplifiers.
The onlt series resonant circuits I have found in these radios are at antenna inputs. The se are used to shunt the IF to ground. You don't want to be receiving IF at the antenna as it is always an interfering signal in that place.

Best regards,

Bill Grimm

:Hi Daniel,
: Easy. All are parallel circuits, both transformers and both primary and secondary.
: The primary of each transformer provides a DC path through its windings to the plate of the tube at its input. In octal terms that is the 12SA7 for the input transformer and 12SK7 for the output transformer. The secondaries are in the grid circuits of the down stream stages. In octal terms that is the 12SK7 for the input transformer and 12SQ7 for the output transformer.
: Each present the maximum impedance at the IF. This provides the maximum voltage to the tubes, which are voltage amplifiers.
: The onlt series resonant circuits I have found in these radios are at antenna inputs. The se are used to shunt the IF to ground. You don't want to be receiving IF at the antenna as it is always an interfering signal in that place.
:
:Best regards,
:
:Bill Grimm
Dear Bill, Thank you for the information!!!
Have a nice weekend
Daniel