Technics linear help needed

Discussion in 'Turntables' started by dannyr, Jun 14, 2018.

  1. dannyr

    dannyr Active Member

    Messages:
    268
    Hi. I have a SL-7 with a snapped drive rope that I'm dying to get running and enjoy. I made a new one out of beading chord but the stylus won't change groves when playing a record. It will cue back and forth though. Will this happen if it made it a bit too loose or is it probably something else? What I'd do for an original replacement part.... Thanks

    Dan
     

     

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  2. SoundsAlike

    SoundsAlike Super Member

    Messages:
    1,854
    Location:
    Greensboro, NC
    Honestly, if you've made it that far with an SL-7, you probably know more about the workings than anyone else here


    Good luck
     
  3. dannyr

    dannyr Active Member

    Messages:
    268
    Hi SoundsAlike. Thanks for the reply. The unit is a bit of a pain in the butt to figure out because I can't watch the inner working while I test it:(. I really wish that I could find the general length that the tonearm rope drive cable has to be.
     
  4. Hugo65

    Hugo65 Active Member

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    124
    Where is Fred when you need him?:dunno:
     
  5. gadget73

    gadget73 junk junkie Subscriber

    Messages:
    36,441
    Location:
    Southern NJ
    Is the drive belt for the arm in good shape? When I had an SL-5, it had tracking problems that I chased to a stretched belt.
     
  6. dannyr

    dannyr Active Member

    Messages:
    268
    I replaced the drive belt and cleaned and lubed the arm guide rail while I was in the unit. I'll try to tighten up the rope drive and see if it works any better.
     

     

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  7. absolon

    absolon Super Member

    Messages:
    2,199
    Location:
    Lotusland
    Travel during cueing is controlled by the cueing switches and stops. The tonearm motor is activated during play by offset sensors that activate when the tonearm angle changes as the stylus is moved along in the grooves. It sounds like that is where your problem lies. See page 14 of the VE service manual (SM page no., not PDF page no.) for some initial info and adjustment procedure.
     
    Pio1980 likes this.
  8. UncleBingo

    UncleBingo AK Subscriber Subscriber

    Messages:
    943
    Check the stylus/ set stylus tracking force before cocking around with the other stuff. Did you clean up the hardened grease everywhere?
     
  9. dannyr

    dannyr Active Member

    Messages:
    268
    Thanks for all the replies.

    Absolon, do you know what I can sub for the "1mm pitch record" used in the adjustment procedure?

    Edit, I did some research and I can sub something with smaller spaced groves like .5mm and cut the voltage in half. I think that a Cardas test record I have has a track with .33mm spacing.

    Uncle, i did clean it pretty well and regreased. made sure that the tracking force was set to 1.25 according to the indicator arrow. I figured that it not advancing where ever that I put the stylus down probably meant that I didn't do the drive drop tight enough or that it was out of adjustment.

    Pretty neat machine.
     
    Last edited: Jun 15, 2018
  10. absolon

    absolon Super Member

    Messages:
    2,199
    Location:
    Lotusland
    Before you start electrically adjusting I'd recommend you identify the relevant parts and go over the mechanism carefully to ensure it is working freely and all connections are good. It's been so long that I can't remember the specifics of how it all works but I did rebuild an SL-7 that suffered a similar problem (among many others) and I didn't need to adjust the mechanism. There was some other little mechanical problem that, given my lack of clear memory of how it was fixed, was easily solved.

    I hope you're successful, they are really nice TTs.
     
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  11. dannyr

    dannyr Active Member

    Messages:
    268
    I'll double check everything. i am hoping that the rope drive i made has too much slack.
     

     

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  12. Gary Francks

    Gary Francks Active Member

    Messages:
    253
    There is a specific way of refitting the drive cord around the drive drum so that it winds on and off cleanly as the arm moves.
    Get it wrong and I believe it can get stuck causing the drive belt to slip On the motor pulley
    On my SL-7 the pulley on the motor shaft wasn't tight and needed removing and reattatching with loctite.
     
  13. stanwebber

    stanwebber New Member

    Messages:
    39
    isn't the drive rope attached to the drum gear via a small spring which keeps the rope taught? if the rope can cue the tonearm back & forth without issue via the buttons that should be enough for normal operation. i would look elsewhere, maybe the long mechanical bracket attached to the tonearm that triggers the offset angle sensors or the sensors themselves?
     
  14. dannyr

    dannyr Active Member

    Messages:
    268
    Gary, I noticed that the gear attached to the worm gear was slipping so I glued it on. it helped me be abled to cue but not go across the record while playing.

    Stan, I'll have to look into the mechanical bracket. Should I take the arm out to look at the sensors?
     
  15. stanwebber

    stanwebber New Member

    Messages:
    39
    actually, i was conflating 2 different arm/rod mechanisms. there is a short tab attached to the tonearm which triggers the offset angle sensor to advance the arm. then there is a very long rod attached which connects to the rest position microswitch on the opposite side of the carriage. there is also a reset (lid open/closed) microswitch which can cause things to stop working although if the tonearm actually drops on a record you can rule this out.

    i currently operate an sl-3 (sl-n15), sl-6, sl-q6 and sl-j33 which have nearly identical mechanisms and i've never had to adjust the servo gain/offset voltage nor would i expect to unless the offset sensor pcb had been removed/replaced.
     
    Last edited: Jun 17, 2018
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  16. dannyr

    dannyr Active Member

    Messages:
    268
    I attempted to clean the sensor on top of the arm and unfortunately it didn't help so I went to try to do the servo adjustment as outlined on page 14 of the service manual. I was able to adjust vr302 correctly to get .72v but moving vr301 while playing a record with wide groves had no effect on the voltage at all. It just stayed at .670v. even though I wanted to get it lower due to playing a .333m grove track. Oddly when the trim pot was moved counterclockwise enough the arm would move quickly across the record but the voltage wouldn't fluctuate. I wonder if it's fixable.
     
    Last edited: Jun 17, 2018

     

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  17. stanwebber

    stanwebber New Member

    Messages:
    39
    i would be encouraged by any movement of the arm towards the center. perhaps the pot is dirty....use a contact cleaner and move it between stops a couple times.
     
  18. dannyr

    dannyr Active Member

    Messages:
    268
    Okay. sprayed out the trim pot. it still has no effect on the voltage reading. hmm.
     
  19. stanwebber

    stanwebber New Member

    Messages:
    39
    alright, i downloaded the sl-7 service manual to look at the instructions and the servo gain/offset voltage adjustment is kinda tedious. i don't think any of the sl-3, sl-6, sl-q6, sl-j3 or sl-j33 models actually require a test record to adjust. the arm which triggers the offset angle sensor is a known length so the adjustment is made with it centered then moved to it's widest detent.

    i would guess that you're not getting variance from the vr301 pot because the offset angle adjustment screw position isn't centered and not allowing a range of inward movement that will affect the voltage (using a test record with less than 1mm grooves is probably exacerbating this). on the previous page in the service manual try performing the instructions for step 2 'offset angle adjustment of tonearm (see fig. b.)' and then readjust the servo gain/offset voltage. in fact, before admitting defeat i would go thru all the tonearm adjustment steps in the order presented.
     
  20. stanwebber

    stanwebber New Member

    Messages:
    39
    you might even overcompensate the position of the offset angle adjustment screw in the other direction past center to see if you get any voltage variance from vr301 in the event that something under the cover got sprung out of alignment.
     

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