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Diagnosing Tuner Board questions

tuner board diagnosing repair problems lasonic 920

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#31 caution

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Posted 06 February 2020 - 12:53 PM

Indeed - an air core coil right next to a screw hole, that's just asking for trouble!



#32 Superduper

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Posted 06 February 2020 - 02:07 PM

Hmm.  Somebody took a short-cut, cut off the diode from the top side, and replaced it by soldering a new diode by tying the leads to the old snipped leads instead of just installing it right.  Diodes in tuners are usually quite specific.  Wonder whether it was a compatible replacement since there's no SM, no parts list, and diodes are usually very difficult to identify as they often don't have markings.  It's not an uncommon repair technique to snip and tie, but usually only on very difficult or poor access repairs and really on a repair like this, shouldn't have been prohibitively difficult to access the rear.  Probably lazy.



#33 hopey

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Posted 06 February 2020 - 07:00 PM

It makes me wonder if you re-sweated the original IC's on the board would that have fixed the problem?

 

As this has been worked on before maybe static could have fried the chips?



#34 Lasonic TRC-920

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Posted 18 February 2020 - 09:17 AM

It makes me wonder if you re-sweated the original IC's on the board would that have fixed the problem?

 

As this has been worked on before maybe static could have fried the chips?

 

I had crawled over all three of these boards with magnifying glasses, I did resolder a few points, but these looked ok.





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