Technics Servo Drive Modifications

antiquekid3 · 20th May 2010, 05:20 AM

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 not...it 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.

Thanks!

Kyle

jrevillug · 21st May 2010, 02:34 PM

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.

20th May 2010, 05:20 AM	#1
antiquekid3 diyAudio Member Join Date: Feb 2010 Location: Alabama	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 not...it 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. Thanks! Kyle

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21st May 2010, 02:34 PM	#2
jrevillug diyAudio Member Join Date: Aug 2006	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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