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how to: calibrating an SL7 tonearm

Posted: 06 Mar 2014 23:46
by lensmanMK2
last night decided to finally have a crack at calibrating the tonearm servo on my SL7,problem is this needs a 1mm pitch test record,probably a special from technics.

set to using the service manual on here and found a few things out of place,for example step 3 on the tonearm calibration has nothing to do with the tonearm height,but is how to calibrate the offset,which needs to be done before you start on step 4 (actual servo calibration)

calculating the centre offset voltage is a bit strange too,as the example values are way off from what i got (15v opposed to 1.27 in my case) so dont be worried if you get something strange showing up on the meter.

not having a test record i decided to do step 4 by ear,for this id recommend a good pair of headphones! the record i used ws ultravox:the best of,but it doubt it would matter much.

when it comes to adjusting vr301 the best sound quality was at the edge of the first 3rd of the trim pot;that is turning it from completely counter clockwise then to a clockwise direction.

you'll know when you reach the outer edge when the carrier stops moving;allow a few seconds in between adjustments,then slowly back off counter clockwise until the carrier moves suddenly to catch up with the tonearm position.

this has improved the sound of my sl7 no end,its gained a lot of dynamic range,better bass and great decay esp on cymbals and synths.stereo spread has suffered but been replaced by rock solid tight instrument placement,spent most of the evening trawling though records!

hope this comes in handy for fellow sl7 owners.

Re: how to: calibrating an SL7 tonearm

Posted: 07 Mar 2014 16:38
by fscl

=D> =D> =D> =D>

Always thought the service manual made this a bit more difficult than necessary, I guess if you have a factory filled with workers and lots of calibrated 1mm LPs handy it would be easy to do, however, this is more of a "real world" solution.

Funny, I've never had to adjust the servos on most all Technics linears I've touched. It's the tired lubrication, dirt / dust and worn rubber that need tweaking / renewal.

Thanks again ! =D> =D> =D>

Fred and going to cross link this with the SL-7 topic so it doesn't slip into obscurity... :?

Re: how to: calibrating an SL7 tonearm

Posted: 07 Mar 2014 17:14
by lensmanMK2
cheers fred :)

this was just to bring it back "in to spec" as much as i could. no tracking probs,but i thought id do it after noticing a big difference on my sl5 after adjusting the servo back to factory.

one more thing ive noticed is the carrier will now snake a lot more more and keep the tonearm steady when tracking an off centre lp,so might be another thing to look for.

Re: how to: calibrating an SL7 tonearm

Posted: 03 Apr 2014 03:54
by blueworm
Funny these are the exact things I experienced when I rebuilt my SL-10. The service manual had some really wierd values in it. Ended up doing it by ear and testing with what hifi test record.