FT-101B Audio

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FT-101B Audio

Postby KL7IGB » Wed Mar 15, 2017 11:55 pm

I am in the process of giving my long-neglected FT-101B (my first store-bought radio purchased new in April 1975) some TLC and am having some trouble understanding the wiring of the audio headphone jack. I've seen the note in the FoxTango service manual .pdf about the incorrect factory wiring on some of those jacks and mine was one of them that would not shut off the speaker. Unfortunately, in the rush of things last week I un-soldered the wiring on the jack and then lost my sketch of what was connected where. Heavy sigh.

I deleted a couple paragraphs of terminal ID stuff here that nobody could possibly be interested in.

I'm now trying to figure out how to reconnect the jack in my radio. It seems simple enough. Connect the audio input (White/Green) from the AN214 to both the tip and ring terminals and the speaker lead (Green) to either one of the switching contacts and we should be golden, but what are those resistors about, the 10 and 100 ohm ones? Anyone know? It looks to me (following the schematic) like, with no phones plugged into the jack, the 10 ohm is bypassed through the switching contact and the ring to the speaker, which is to say ignored, and the 100 ohm is connected through the tip and tip switching contact to, well, nothing. With phones plugged in, the audio will pass from the common feed through 10 ohms and the ring to one headphone speaker and through 100 ohms and the tip to the other. That doesn't make any sense to me. Can anyone shed some light on what's going on here? What are the resistors for? Can I redirect the resistors to a better place?

Note added 17 March 2017
Well, I got impatient, wired the jack as it seemed to me it should work (tip and ring to audio input, tip switching contact to speaker, no resistors ), and tried it. It seems to work fine so barring compelling info to the contrary I'll probably leave it that way.
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