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Old 13th Jun 2019, 8:59 am   #26
Radio Wrangler
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Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 12,711
Default Re: No LW/MW receive - Sony ST-S311

The resonator on pin 15 isn't an oscillator. It's emitter decoupling for the S meter amp... I think it's to make the S meter response very narrowband so auto search tuning finds the carrier of a signal to stop on. I don't think you'd see much signal there on it as it's used to do a low Z dip at the carrier freq. This is also a long way downstream of the IF filter.

Seeing 450kHz without mod on the IF filter looks very wrong.

IF is 450kHz, so LO should be 450k above tuned freq. Can you wave aprobe in the air near pins 18 and 19 and get a sniff of it?

David (About to go QRT and drive up to Scotland)

The IC datasheet is clearer about what's going on than Sony's schematic.
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