pye: Pye Fenman 2: how does the FM mixer work?
ID: 146405
This article refers to the model: Fenman 2 (Pye Ltd., Radio Works; Cambridge)
pye: Pye Fenman 2: how does the FM mixer work?
03.Aug.07 21:54
0
I have just finished uploading the schematics for the Pye FenMan 2, prompted by a friend purchasing an example of this radio and needing the service information for it.
Whilst copying it and studying the FM tuner circuit, which is rather different from the typical double-triode arrangement used in many sets, I noticed that there was no immediately obvious arragement for coupling the oscillations from the triode section of the ECF80 into the pentode section. I assume that there is an internal shield between the two sections and the two sections are electrically isolated, so how does it work? I did wonder if the RF choke in the decoupling of the screen grid of the ECF80 had any bearing on the operation of the mixer? In some television tuners a small value of capacity (ca. 2pF) couples the two sections. Am I missing something obvious here?
I have included an extract of the circuit below, if anyone needs the circuit values I can add those later. All your thoughts are gratefully received!
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Whilst copying it and studying the FM tuner circuit, which is rather different from the typical double-triode arrangement used in many sets, I noticed that there was no immediately obvious arragement for coupling the oscillations from the triode section of the ECF80 into the pentode section. I assume that there is an internal shield between the two sections and the two sections are electrically isolated, so how does it work? I did wonder if the RF choke in the decoupling of the screen grid of the ECF80 had any bearing on the operation of the mixer? In some television tuners a small value of capacity (ca. 2pF) couples the two sections. Am I missing something obvious here?
I have included an extract of the circuit below, if anyone needs the circuit values I can add those later. All your thoughts are gratefully received!
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26.Aug.07 04:12
Mike,
having studied your circuit and the Trader sheet I sent
you, nothing seems obvious; though the Trader sheet does confirm the coupling is external.
My best guess would be a carefully arranged coupling between osc. and mixer coils.
I had one of these sets for many years, superb radio, never any bother - though I did replace all the little Hunts capacitors!
Regards,
John Turrill.
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Lack of information
27.Aug.07 19:59
Dear Mike,
additionally I looked through the alignment instructions of the FENMAN 2 but did not find any reference note (as expected). Therefore my idea is only a vague "direction of thought" and not necessarily the solution of the problem. Mr. Erb does not like speculation, okay, but what shall we do ? I also think that the coupling is not obvious as already assumed. We would need more information about the mechanical construction, mounting arrangement of the coils as John Turril told us, etc., or figures. But nevertheless:
Please look at the schematic inside of the following website by the use of search term "EQ 80". In this interesting publication "UKW-Empfänger mit Phasenwinkeldemodulation" the author Hans Schulz describes his construction of an FM-receiver with an unusual coupling method of oscillator and mixer with some windings of a wire.
Perhaps you would have to search for a similiar solution, but I am afraid that you would need the original radio to do so.
Best regards
Rolf
additionally I looked through the alignment instructions of the FENMAN 2 but did not find any reference note (as expected). Therefore my idea is only a vague "direction of thought" and not necessarily the solution of the problem. Mr. Erb does not like speculation, okay, but what shall we do ? I also think that the coupling is not obvious as already assumed. We would need more information about the mechanical construction, mounting arrangement of the coils as John Turril told us, etc., or figures. But nevertheless:
Please look at the schematic inside of the following website by the use of search term "EQ 80". In this interesting publication "UKW-Empfänger mit Phasenwinkeldemodulation" the author Hans Schulz describes his construction of an FM-receiver with an unusual coupling method of oscillator and mixer with some windings of a wire.
Perhaps you would have to search for a similiar solution, but I am afraid that you would need the original radio to do so.
Best regards
Rolf
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fenman11
15.Sep.07 13:50
hi mike, many of these fenman 11s were made in the pye factory in a little village in the foothills of the dublin mountains ,and exported to the uk and further , hope this doesent sound[ speculative] but a common fault in that model was the wave change switch , u could get a signal on all wavebands and nothing on vhf , might be worth a check for corrosion or dry joints at the wave change switch , regards maitiu.
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