Gemini FM 64 radio mike Soldered in a GP SOT23, BCW31 topcode D1. On 3V the LED flashes on switch on, goes goes continuous if V drops to 1.4V and current goes well over 100mA before that. With 3V, current draw is 69mA and 68mA without the electret mike plugged in but no change in draw with tapping of mike. Nothing on the LM317 so I will assume that is for DC feed for rechargeables, not used for the main circuitry.
Dug out an ancient early portable colour TV, retained for just such a purpose. So old it has a VHF rotary tuner built in as well as UHF. But of course nice old mechanical rotation for VT to tuner block, so can play around as much as you like detuning either side to try and get some sort of audio demodulated. At the top of the range around ch 68 a strong signal including interference pattern on picture,from the other end of the room, all going on switching off the radio mike. No amount of fiddling of de-tune would get even a semblance of sound on tapping the mike nor change of interference pattern on screen. At this stage without proper test equipment I will assume working entirely until the owner tells me otherwise. Still don't know what the third position of the slide switch is. Maybe only
2 positions used of the 3, going by the length of slot in the outer bezel, but the plastic widget that extends up from the pcb slide sw is missing, hence plenty of space to scrape a screwdriver around inside. The surround Al of the slide sw was so randomly scraped I thought it was brush finished when I first saw it, hence probably hundreds of screwdriver activations. Now to bodge up a widget
-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on
formatting link