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Thread: Drilling a hole for tonearm

  1. #1
    Join Date: Mar 2016

    Location: Brighton, UK.

    Posts: 1,584
    I'm Mike.

    Default Drilling a hole for tonearm

    My NAS Interspace armboard and my new to me Nima tonearm have been sent to NAS so they can see how best to fit a new armboard for me - or add to/adjust the current one. So this is a good chance to finally get around to fitting my Jelco 750 to my newly acquired (6 months ago ?) Garrard 401. I have an old SME type wooden plinth - lead lined. So I need to drill a new hole for the Jelco, I have a template, so the distance is fine, but I'm just wondering does the vertical placement matter? Obviously it will sit at somewhere around the top right hand corner, but how specific does it have to be? And how do I know exactly where to place it? Is it slightly above right hand corner? Or may'be right on the corner, or below?

    You can see from pics that right on the corner the armboard would be a bit too close to the 401 to fit exactly at 229.

    IMG_20191204_214752930_HDR by Mike Van, on Flickr
    IMG_20191204_214759261_HDR by Mike Van, on Flickr
    IMG_20191204_214816691_HDR by Mike Van, on Flickr
    Current system. NAS Interspace/Garrard 401/Jelco 750 or Roksan Nima /Nagaoka MP 200/Graham Slee Era V. CDP - Mission PCM 7000. Amp - Audio Innovations S500. Rega Mira/Brio. Audio Note J's/Chario syntar towers. QED XT40 speaker cable/Straight wire interconnects.

  2. #2
    Join Date: Jul 2010

    Location: Cheltenham

    Posts: 954
    I'm Charlie.

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    Use the setting in the middle picture ie with the pivot to spindle at 229 mm. The bottom picture setting will mean that the geometry will be wrong.
    R2R: Studer A820 1/2 inch 2 track; Otari MTR-12 1/4 inch 2 track; Sony APR 5003; Sony APR 5002; Studer A807/II. Vinyl: Platine Verdier Allaerts MC1B/Schroeder Reference & Model 2 Decca C4E/Hadcock 228 TRON Seven Reference phono. Keith Monks MkII RCM Other analogue source: Nakamichi Dragon with ANT4066 mods. Amplification: TRON Meteor preamp TRON Voyager 20B SET power. Speakers: Avantgarde Duo. Digital: computing at last with Prism Sound Lyra 2 A2D converter

  3. #3
    Join Date: Dec 2017

    Location: Lincolnshire

    Posts: 344
    I'm Martin.

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    Is it for a 9” Jelco as I thought they were 214mm spindle to pivot?

  4. #4
    Join Date: Mar 2016

    Location: Brighton, UK.

    Posts: 1,584
    I'm Mike.

    Default

    Quote Originally Posted by scotty38 View Post
    Is it for a 9” Jelco as I thought they were 214mm spindle to pivot?
    Yes 9", I did see somewhere on the interweb a similar discussion, mentioned info from the Jelco website giving the 'effective length' of the 750 as 229, whatever effective length is. EDIT - Just measured the distance between spindle and middle of armboard on my old NAS and it is indeed 214, then I had the bright idea of measuring the distance on the Jelco 'ruler' - protractor? Whatever its called, that was 214mm as well! So 229m being the 'effective length, I guess is with headshell?
    Last edited by Mikeandvan; 04-12-2019 at 23:30.
    Current system. NAS Interspace/Garrard 401/Jelco 750 or Roksan Nima /Nagaoka MP 200/Graham Slee Era V. CDP - Mission PCM 7000. Amp - Audio Innovations S500. Rega Mira/Brio. Audio Note J's/Chario syntar towers. QED XT40 speaker cable/Straight wire interconnects.

  5. #5
    Join Date: Mar 2016

    Location: Brighton, UK.

    Posts: 1,584
    I'm Mike.

    Default

    Quote Originally Posted by topoxforddoc View Post
    Use the setting in the middle picture ie with the pivot to spindle at 229 mm. The bottom picture setting will mean that the geometry will be wrong.
    OK thanks, that would mean the armboard set slightly down from the corner.
    Current system. NAS Interspace/Garrard 401/Jelco 750 or Roksan Nima /Nagaoka MP 200/Graham Slee Era V. CDP - Mission PCM 7000. Amp - Audio Innovations S500. Rega Mira/Brio. Audio Note J's/Chario syntar towers. QED XT40 speaker cable/Straight wire interconnects.

  6. #6
    Join Date: Dec 2017

    Location: Lincolnshire

    Posts: 344
    I'm Martin.

    Default

    Quote Originally Posted by Mikeandvan View Post
    OK thanks, that would mean the armboard set slightly down from the corner.
    Just double check before you drill as I'm sure they're not 229mm....

  7. #7
    Join Date: Mar 2016

    Location: Brighton, UK.

    Posts: 1,584
    I'm Mike.

    Default

    Anyone else offer any advice? I really want to play these classic James Brown 70s lps I just off Ebay!
    Current system. NAS Interspace/Garrard 401/Jelco 750 or Roksan Nima /Nagaoka MP 200/Graham Slee Era V. CDP - Mission PCM 7000. Amp - Audio Innovations S500. Rega Mira/Brio. Audio Note J's/Chario syntar towers. QED XT40 speaker cable/Straight wire interconnects.

  8. #8
    Join Date: Nov 2011

    Location: Seaton, Devon, UK

    Posts: 6,463
    I'm Adrian.

    Default

    Quote Originally Posted by Mikeandvan View Post
    Anyone else offer any advice? I really want to play these classic James Brown 70s lps I just off Ebay!
    Just in case you do not realise the cut out in the Jelco mounting boss should be facing the front of the plinth, it is for the arm lift, you need it in the correct position before you mark and drill the mounting holes for the bolts.

    Once you have drilled a hole for the arm shaft (slightly oversized), offer up the arm sat in the mounting boss onto the plinth and then use the template again to get the centre of the arm spindle exactly at the 229 mark, you may need to find a way to extend the platter spindle so to keep the platter parallel to the platter. Once you have done this with the mounting boss cut out in the correct position you can mark the holes for mounting bolts.

    I hope the above makes sense.

    Adrian
    Listening is the act of aural discrimination and dissemination of sound, and accepting you get it wrong sometimes.

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  9. #9
    Join Date: Apr 2016

    Location: Gravesend and France

    Posts: 1,433
    I'm paul.

    Default

    I thought it was agreed it's 214 pivot to spindle, effective length is pivot to stylus. When you say vertical position, do you mean with the plinth standing on the front edge like a vertical turntable that would probably be linear tracking. I usually use a pencil to draw an arc at the pivot to spindle distance then decide where the arm works best, for example to check the tail end of the arm doesn't foul on anything like a cover and check the headshell doesn't foul on the controls.
    Bakoon 11R Denon DP80 Stax UA-70 Shure Ultra 500 in a Martin Bastin body with jico stylus, project ds2 digital Rullit silver lab 8 field coils in tqwt speakers

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  10. #10
    Join Date: Dec 2017

    Location: Lincolnshire

    Posts: 344
    I'm Martin.

    Default

    Yep not sure where spindle pivot of 229 keeps coming from

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