Drilling a hole for tonearm

[Mikeandvan]

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.

https://live.staticflickr.com/65535/49169870878_706bb890ff.jpg (https://flic.kr/p/2hUYrys)IMG_20191204_214752930_HDR (https://flic.kr/p/2hUYrys) by Mike Van (https://www.flickr.com/photos/145505522@N02/), on Flickr
https://live.staticflickr.com/65535/49170346786_07966892ab.jpg (https://flic.kr/p/2hV1T2L)IMG_20191204_214759261_HDR (https://flic.kr/p/2hV1T2L) by Mike Van (https://www.flickr.com/photos/145505522@N02/), on Flickr
https://live.staticflickr.com/65535/49170580252_5edd954070.jpg (https://flic.kr/p/2hV35r3)IMG_20191204_214816691_HDR (https://flic.kr/p/2hV35r3) by Mike Van (https://www.flickr.com/photos/145505522@N02/), on Flickr

[topoxforddoc]

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.

[scotty38]

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

[Mikeandvan]

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?

[Mikeandvan]

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.

[scotty38]

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....

[Mikeandvan]

Anyone else offer any advice? I really want to play these classic James Brown 70s lps I just off Ebay!

[AJSki2fly]

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

[paulf-2007]

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.

[scotty38]

Yep not sure where spindle pivot of 229 keeps coming from :D :D

[AJSki2fly]

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.

Yep I agree its odd that Jelco mark the setup protractor as 229(effective length) but pivot to spindle is 214, very confusing, but Mike has checked and 214 is the measurement. Yes I agree actually drawing an arc and then deciding the best position is the sensible solution, I was making the silly assumption that you would want the arm parked parallel to the edge the plinth, hence have the arm lift facing the front edge of the plinth.

[Mikeandvan]

https://live.staticflickr.com/65535/49174865156_3481d54400.jpg (https://flic.kr/p/2hVq3bG)IMG_20191205_205448337_HDR (https://flic.kr/p/2hVq3bG) by Mike Van (https://www.flickr.com/photos/145505522@N02/), on Flickr

Seems slightly above the corner is the only way to get the right pivot to spindle distance, any lower and the armboard touches the 401 unit, is it ok in this position? Would it make a difference if it was lower in terms of the angle that the stylus hits the record.

[AJSki2fly]

https://live.staticflickr.com/65535/49174865156_3481d54400.jpg (https://flic.kr/p/2hVq3bG)IMG_20191205_205448337_HDR (https://flic.kr/p/2hVq3bG) by Mike Van (https://www.flickr.com/photos/145505522@N02/), on Flickr

Seems slightly above the corner is the only way to get the right pivot to spindle distance, any lower and the armboard touches the 401 unit, is it ok in this position? Would it make a difference if it was lower in terms of the angle that the stylus hits the record.

The key thing is that the distance from the centre of the spindle to the centre of the arm pivot point is 214mm, which as you have already said is the distance you have at the 255 mark on the template(confusing as it is). The angle as you put it(lateral angle I think it is) that the stylus hits the record will be the same for any position the pivot arm is at 214mm from the centre of the spindle. This is assuming that having set up the arm on the plinth you then set up the position in the head shell correctly using a stylus alignment protractor https://www.vinylengine.com/cartridge-alignment-protractors.shtml

[scotty38]

As Adrian has said, as long as it's placed on the arc scribed by the point actually 214mm from the spindle you'll be fine. Aesthetics are another thing though and I think where you have it in that corner will probably look best.

Having said that why not post pictures, side by side, of where it is now and clockwise just past the top right corner and we can see what would look best?

[awkwardbydesign]

Yep not sure where spindle pivot of 229 keeps coming from :D :D

229mm is the effective length. It means there will be a 15mm overhang. Stylus (229mm) 15mm beyond pivot (214mm). Normal, but variable, depending on arm geometry.

[scotty38]

229mm is the effective length. It means there will be a 15mm overhang. Stylus (229mm) 15mm beyond pivot (214mm). Normal, but variable, depending on arm geometry.

Thanks but I'm well aware of that. I didn't want anyone drilling a hole 229mm away from the spindle.

[paulf-2007]

That gauge could easily confuse, better to get a piece of thin wood or ruler, drill two holes 214mm apart, one hole over the spindle and a pencil in the other, scribe an arc job done. That picture of the gauge at 229 shows the tone arm will not go on the corner, either behind or at the side if there is room

[Barry]

The Jelco 750D arm has an effective length (stylus to pivot) of 229mm, with an overhang of 15mm. Thus the TT spigot to arm pivot distance is 214mm (229 - 15 = 214mm). The installation protractor is marked with the effective length of the arm you are wanting to install, hence in your case '229'.

The null radii (on the alignement protractor) will be 59.1mm and 112.5mm.

Where you drill the hole for the pickup arm won't matter, as long as the distance from the TT spigot is 214mm. Choose anywhere on the arc that doesn't cause the counterweight end of the arm to foul the lid of the plinth, but is not too far in a clockwise sense that makes the pickup difficult to cue.

[Mikeandvan]

Thanks to all replies, the mounting collar is just slightly above the corner of the 401 motor unit, will fit tonearm tomorrow, dunno what it will sound like! I'm expecting to be crap for some reason? Saying that I do have a AG1500 mains regenerator which I've heard can help the 401 motor somewhat. ALso the sme plinth has been lead lined, what I don't get is how many 'posh' 401 plinths have the tonearm connected to the same plinth as the motor unit, surely the vibrations will affect performance? I also won't have much room for a fancy plinth once I get around to buying a proper one, so armboard will need to be close to the motor unit, as it is now.

[Mikeandvan]

Anyone know what size holes to drill for the 3 mounting screws for the Amnonite Jelco collar? Will need to use screws rather than the alan bolts provided as I don't have a tool to make threads.

[scotty38]

I wouldn’t use the set screws into a “thread” in the wood anyway, however you can get inserts that would then take the set screws directly.

As for screw holes it depends what size the screws are, maybe just a bradawl is needed.

Don’t take this the wrong way but step away from the drill until you’re sure.....

[Mikeandvan]

Got the motor unit sitting on sorbothane balls in each corner, feels secure and nicely damped.
https://live.staticflickr.com/65535/49182360717_5a9a8bee8c.jpg (https://flic.kr/p/2hW5smv)401111 (https://flic.kr/p/2hW5smv) by Mike Van (https://www.flickr.com/photos/145505522@N02/), on Flickr

The old SME cut out looks like it just had screws or alan bolts going directly into the wood, so I think that's what I'll do.

https://live.staticflickr.com/65535/49181657968_87f41c915e.jpg (https://flic.kr/p/2hW1Rs9)401 + jelco (https://flic.kr/p/2hW1Rs9) by Mike Van (https://www.flickr.com/photos/145505522@N02/), on Flickr

[Mikeandvan]

I wouldn’t use the set screws into a “thread” in the wood anyway, however you can get inserts that would then take the set screws directly.

As for screw holes it depends what size the screws are, maybe just a bradawl is needed.

Don’t take this the wrong way but step away from the drill until you’re sure.....

If you look at pic above the sme cut out looks like it was just screwed directly into plinth.

[Stratmangler]

That looks like an SME2000 plinth.
Is it well damped?
The old Garrard decks acquired their reputation for rumble because of flimsy plinths such as the SME2000.
Garrard used to mount them to a concrete slab to test them in the factory.

[Mikeandvan]

That looks like an SME2000 plinth.
Is it well damped?
The old Garrard decks acquired their reputation for rumble because of flimsy plinths such as the SME2000.
Garrard used to mount them to a concrete slab to test them in the factory.

I meant having the sorbothane balls in each corner makes the plinth feel secure yet damped. This particular plinth has been modded by previous owner who lead lined the base of it. It is only a temporary plinth and if I think I like the idler sound then I'll buy a plywood plinth.

[scotty38]

Are you sure the screws didn’t have nuts underneath the plinth?

[paulf-2007]

The Jelco 750D arm has an effective length (stylus to pivot) of 229mm, with an overhang of 15mm. Thus the TT spigot to arm pivot distance is 214mm (229 - 15 = 214mm). The installation protractor is marked with the effective length of the arm you are wanting to install, hence in your case '229'.

The null radii (on the alignement protractor) will be 59.1mm and 112.5mm.

Where you drill the hole for the pickup arm won't matter, as long as the distance from the TT spigot is 214mm. Choose anywhere on the arc that doesn't cause the counterweight end of the arm to foul the lid of the plinth, but is not too far in a clockwise sense that makes the pickup difficult to cue.
Technically speaking that protractor is bollocks. It's not for setting the pivot distance but to set the overhang if the headshell has slotted holes to mount the cart. But how can you accurately set it when the tone arm base is fixed to the plinth.

[Mikeandvan]

Tonearm base in place, all looks ok I think, not 100% sure on cartridge alignment, besides I now have another another hurdle, I cannot raise the tonearm high enough for it to be parallel with the platter, as the tonearm cable has a right angle din plug and it cannot pass through the mounting collar, needs another 5mm at least, so gonna have to buy another cable with a straight din plug. Another few days until I can hear those James Brown records I got off Ebay, *** ****!

[Mikeandvan]

https://live.staticflickr.com/65535/49190603642_e4308699d7.jpg (https://flic.kr/p/2hWNGFU)IMG_20191208_233339337_HDR (https://flic.kr/p/2hWNGFU) by Mike Van (https://www.flickr.com/photos/145505522@N02/), on Flickr

Well, the tonearm is not quite high enough, but it''ll do. The cart alignment seems almost spot on. I first played a disco/funk track by Donald Byrd - Dominoes - itself a very uplifting fine example of the genre, and it slightly blew me away, the bass is so good, the whole sound has a propulsive quality, of course I am listening to it through the JVC, so much of it will be from that, but first impressions are this thing boogies seriously, the sound is visceral, has quite an impact. Needs refining, but think I'm a fan.

[scotty38]

Looks good. If the arm is a bit low at the rear it will most likely up the bass a bit.

[AJSki2fly]

https://live.staticflickr.com/65535/49190603642_e4308699d7.jpg (https://flic.kr/p/2hWNGFU)IMG_20191208_233339337_HDR (https://flic.kr/p/2hWNGFU) by Mike Van (https://www.flickr.com/photos/145505522@N02/), on Flickr

Well, the tonearm is not quite high enough, but it''ll do. The cart alignment seems almost spot on. I first played a disco/funk track by Donald Byrd - Dominoes - itself a very uplifting fine example of the genre, and it slightly blew me away, the bass is so good, the whole sound has a propulsive quality, of course I am listening to it through the JVC, so much of it will be from that, but first impressions are this thing boogies seriously, the sound is visceral, has quite an impact. Needs refining, but think I'm a fan.

Is this with the right angle tonearm cable? If it is and the cartridge down at the rear then be careful with warped records if you have any, best to get a one with a straight DIN if you intend to use long term.

[Mikeandvan]

Is this with the right angle tonearm cable? If it is and the cartridge down at the rear then be careful with warped records if you have any, best to get a one with a straight DIN if you intend to use long term.

Yes it is, only using it until I buy a straight one, so just a few days. The bass is overwhelming at the minute, and the sound is a bit raw, so may'be correct tonearm height will correct that, it is down a fair bit at the back, still listenable though.

[Mikeandvan]

Looks good. If the arm is a bit low at the rear it will most likely up the bass a bit.

Yes precisely that.