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Panasonic RX-C52 dead logic control on play


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#1 tapemaster1.875

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Posted 25 October 2016 - 01:24 PM

I have two of these RX-C52's ' cause I really like 'em, but I ruined the logic control play/record functions, by attempting to adjust the speed pot on the tape motor and forgetting to unplug the machine before removing the front circuit board with the logic buttons on it. FF and REW still work. Luckily I have another good unit, so I have been swapping transistors, capacitors, diodes, ic's, and whatever those blue bubble looking things are, and after each swap from the good board to the bad board, and bad to the good board, the bad still won't work and the good one still works. I'm at a loss, here and still have more swapping to do. Does anyone have any other suggestions?

#2 Fatdog

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Posted 26 October 2016 - 04:46 PM

It might be a lost cause.  You have definitely blown something out somewhere.  Have you looked for a service manual yet?  Check with Analog Alley - the owner of that website is a member here: Superduper.

 

http://www.analogalley.com

 

Or, he might chime in here with some advice where to check.



#3 Superduper

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Posted 26 October 2016 - 07:20 PM

You aren't getting results either because you haven't swapped the right parts or that there is damage to the PCB independent of the components.  Additionally, you are swapping one part at a time and putting back afterwards.  How do you know that there aren't a combination of bad components?

 

Try swapping Q402/Q403 together as a pair.  The Logic control IC might need swapping (IC401) but I do not recommend that you do this yourself without proper equipment since they are easily damaged without proper desoldering equipment and I suspect that these are very much NLA which might indeed render this (and your parts source as well) a lost cause if you damage them.  Try those 2 transistors first.