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Technics SL-3200 vintage turntable repair - 45 not working

max1

New Member
Hi, first of all sorry for my lack of skill level regarding this. I have a Technics SL-3200 & the 45 speed is not working, 33 is fine. Was wondering if anyone has any knowledge of the circuitry ? I’ve got it apart & can’t see any obvious cracks/physical damage on any of the PCB’s. I can see from the schematic that the simple 33 & 45 switching circuit share the same path back to IC1 (AN630U). Im not sure how IC1 handles these two voltages though & for what reason only the 33 speed is getting triggered. Maybe I should start by reflowing some of the relevant solder points. Voltages are good for 33 position but seem a bit skewed once in 45 position, however am unsure of correct voltages for 45 position (schematic only indicates 33 position voltages). Just wondered before I went any further if someone has experience with this old AN630 chip ? Grateful for any help whatsoever. The schematic is attached.
 

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rjenkinsgb

Well-Known Member
Most Helpful Member
I'd try giving the two pots/presets a slight movement either way & operate the switch a few times, to see if it's just a bad wiper connection.

The pots appear to be the only thing different between the two speeds?

[Edit - typo]
 
Last edited:

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
Possibilities:

VR4. The wiper opened. leave S2 in off and measure the resistance.

S2 oxidized. Leave S2 off and make connection with external jumper.

Clean the potentiometer and switches. Deoxit.
 

max1

New Member
Thanks for the replies. Yes I was thinking there shouldn't be much to go wrong but I'm not familiar with how IC1 works & so wanted to check. Great - ill take all your advice & see what I can find. Thanks again.
 

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