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Old 20th May 2010, 05:20 AM   #1
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Location: Alabama
Default Technics Servo Drive Modifications

Hey guys,

My physics teacher just traded me an SL-1400 for my SL-Q200. I figured the SL-1400 was an all around better turntable. I don't know if I'm going to regret this eventually or seems to be a higher quality TT, and I like being able to vary the speeds. The SL-1400 seems to have more variety in cartridges.

However, looking at the schematic, I have found that it should be easy to modify the 45 rpm to play 78s. I would like to modify my turntable to keep the 33 rpm speed the same but have the 45 speed vary from ~40 to ~85 rpm. Is this possible? I'm hoping to use the existing pots.


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Old 21st May 2010, 02:34 PM   #2
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Not knowing the schematic, I'd guess that it is indeed possible to change the circtui to allow 45-85rpm adjustment.

However, I would also guess that the potentiometer would need to be a different value to increase the range of adjustment from +-10% (ish) to -0% +100%.

If the potentiometer is part of a potential divider including extra resistors it may be possible to alter the fixed resistors to give this bigger range, but you'd have to watch the current through the pot - and maybe the input voltage to comparators or similar.

This is the sort of change that needs careful design to be reliable really.
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