Output stage for a Mono FM tube tuner

[oldglide]

Since this is a tube question, I hope this is the correct forum. Question regarding capacitor values for the output stage of a mono FM tube tuner. The output of the ratio detector is capacitor coupled, .01uF, to the cathode of a 6BN8 through a voltage divider then capacitor coupled to the output through a .05uF as indicated on the schematic. The actual output coupling capacitor is labeled 224K. I can't seem to find the right conversion. I think it would be either .22uF or 2.2uF. In any case do these values seem appropriate for this type of circuit? Circuit design is from 1961. Thanks

[DF96]

224K is 0.22uF. I don't think this marking scheme was used in 1961 so the cap is probably part of a repair. The value is not critical, provided the load is high enough in resistance.

To say any more we would need to see the circuit.

[oldglide]

I kinda thought so but wasn't sure. The original value, .05uF was from the original 1961 schematic. I kind of figured the 224K was a replacement. Pics to follow. Thank you.

[oldglide]

OK Here's the diagram of the output stage of my tube tuner. The output of the ratio detector goes to a volume control and also to the front end for an AFC control. Any info on the values of these capacitors would be greatly appreciated. Thanks

[Chris Hornbeck]

Somewhere there needs to be a 75uS de-emphasis (for USA). Not enough is shown to be certain, but C36 might be involved.

All good fortune,
Chris

[DF96]

Yes, not enough shown to be clear what is happening.

[Chris Daly]

I have looked at a Quad FM1 schematic which was also in production in 1961.

I find very similar values to you describe. In the FM1 The Acoustical Manufacturing Company ( Quad ) used .04uf coupling capacitor then 220k in series, to the audio out - with 100k to ground and 1000pf in parallel with that 100k resistor.

Cheers / Chris

[oldglide]

The broken line above the ouput stage indicates a sealed package that contains all the de-emphisis and high frequency suppresion, above audio frequencies, circuitry. The manufacturer calls this a P.E.C., "Packaged Electronic Circuit". The manufacturer states "The use of a P.E.C. is to eliminate any variations in performance caused by variations in wiring techniques". I quess all kit builders don't build things the same.