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Old 16th Jun 2019, 12:13 pm   #34
Mike. Watterson
Heptode
 
Join Date: Dec 2014
Location: Limerick, Ireland.
Posts: 901
Default Re: No LW/MW receive - Sony ST-S311

Quote:
Originally Posted by Martin G7MRV View Post
... the IF amp input pin, which was about 1v too low. This connects to one side of the ceramic filter...

Checking the filter was none too easy - the IF filtering is a Toko module consisting of a tuned IFT and a ceramic filter, electrically separate but packaged in the same plastic housing. Had to unsolder the entire thing and remove it to test.

The leg of the filter that goes to the IF amp input pin reads 3k to ground! The other leg infinite at DC.

Bypassing the IF filtering entirely with a 10n cap, and the set now indicates tuned with a signal greater than 150uV (-65dBm).
I did suggest checking it. They do seem to be fragile and go open circuit on their own.

You could fit a ceramic filter of same frequency out of a £6 radio. Better than a capacitor
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