Help required with Jelco 750D

[Spectral Morn]

Hi Guys


As the Jelco 750D arm (maybe all Jelco arms) does not come with instructions as such can someone post some photos of a 750D mounted on a Technics 1200/1210 from above. I need to see if the arm is mounted with the back of the arm (where the counterweight is) is mounted square to the back of the deck.

In essence is the arm mounted with an imaginary straight line from back to front of the deck, with the straight bits of the arm (counterweight stub and arm before the s starts) on a middle line square to the back and side of the turntable.

This being my first S shaped arm I am concerned that I may have it mounted incorrectly/ or a tad off.

Any photographic help gratefully received.


Regards D S D L

[worrasf]

Hi,

Have attached a couple of piccies.
I use the TimeStep armboard and Hugo's modified collar.
I have it setup so the horizontal bar holding the cueing mechanism is directly inline with the 2 front screws on the armboard.
This sets up the arm straight front - to back.

Steve

[Spectral Morn]

Yes that looks more or less like how I have done it too, though I am not using a Sound HiFi armboard.

I have been scouring the net for photos of Jelco's and there are a lot of arms set up so that they are pointing out or in a few cases appear to be pointing in. However no photos from above.

Cheers D S D L

[Marco]

Hi Neil,

I'd love to help, but Del's the one with the digital camera, and I don't have a scooby-doo how to put pics from it onto my laptop....

So you've got a Jelco now of your own? :)

Marco.

[Spectral Morn]

Hi Neil,

*I'd love to help, but Del's the one with the digital camera, and I don't have a scooby-doo how to put pics from it onto my laptop....*

So you've got a Jelco now of your own? :)

Marco.


Yes I saw Chivas Jelco for sale awhile ago had a Technics so thought it was worth a punt.

In the case of your Jelco if you look from above (in your case via a tall ladder :lol::lol::lol::lol:) have you set the arm up so that the back of the counterweight is square to the back of the tt and the right side of the weight square to the right side ? Or do these arms sit pointing out a tad or pointing in towards the platter a tad ?

Where Jelco fail here is no instructions....SME score 10 out of 10 here.... heck even Graham scores too with good instructions (not SME standard but does anyone else come close to them in this area ?)

Also info on compatible carts is also few and far between....DL130 and SPU we know via you but what else is suitable ? or not as the case maybe.

This is a learning curve for me and I am quite happy to say where my knowledge experience is thin and on Jelco it is very thin..... This is why I want to expand it and getting a Jelco was a logical way to do it. Plus the Neglex arm cable I am sure can be improved on.....but that's for another day.

So my jury is still out on the Jelco at the minute.


Regards D S D L

PS *You need to sort that out Marco if I can do it......you can do it.....its easy !*

[Marco]

I'll have a wee peek-ette after I've finished watching The Apprentice :)

Marco.

[The Grand Wazoo]

Am I missing something here?

Does it actually matter? - Surely during use, the arm will rotate about the same axis as the one that you are adjusting it by. As long as it's able to traverse the playing surface of a record, it shouldn't matter whether it's pointing in, straight up & down or even stuck out at 90 degrees to the plinth.

[Marco]

In the case of your Jelco if you look from above (in your case via a tall ladder ) have you set the arm up so that the back of the counterweight is square to the back of the tt and the right side of the weight square to the right side ? Or do these arms sit pointing out a tad or pointing in towards the platter a tad ?


It's pointing in towards the platter (a tad) on both :)

What protractor are you using?

Re: the Jelco with other cartridges... Basically, if you use a medium-mass headshell, such as the one supplied with the Jelco, it'll take any cartridge you like. It's a high quality tonearm with very good bearings.

The new AT MCs would be very good, and so would Deccas (I've tried that, with great success), as would pretty much anything you could think of.

The main reason why the Jelco SA-750 works so well with SPUs and DL-103s is because it has a detachable headshell, and hence you can buy high-mass detachable headshells (such as the Ortofon LH 9000 I use) that optimise the performance of the latter (DL-103).

Elegantly adding mass on a conventional fixed headshell low to medium-mass arm is more difficult to achieve. And the former (classic SPU), of course, needs an SME-type detachable headshell arm to work, period! ;)

Marco.

[Spectral Morn]

Am I missing something here?

Does it actually matter? - Surely during use, the arm will rotate about the same axis as the one that you are adjusting it by. As long as it's able to traverse the playing surface of a record, it shouldn't matter whether it's pointing in, straight up & down or even stuck out at 90 degrees to the plinth.

I tried a number of positions for the arm and it did make a difference in regard to lining up the cartridge using several alignment protractors I have. The position it is in at the minute allowed set up of the cart at point A and point B so that the stylus was nearly 100% parallel to the protractor lines.

I was hoping for some more info from more experienced Jelco owners if the position I have settled on is the optimum one or not.


Regards D S D L

[The Grand Wazoo]

Oh, OK - so I was missing something. The centre of the arm pillar is not co-incident with the axis of the horizontal bearing then?

[Spectral Morn]

The protractor is one I have had for 20+ years and I can't remember who made it.

Point A is at 2.60 and point B at 4.76 if that helps :scratch:


Regards D S D L

[Marco]

I was hoping for some more info from more experienced Jelco owners if the position I have settled on is the optimum one or not.


Remember that Creepy fitted mine ;)

If you want in-depth info on this sort of stuff, Hugo (Shuggie) is yer man!

Marco.

[Spectral Morn]

Hopefully he will see this thread and make a few comments.....



Regards D S D L

[Marco]

PM him, dude - he's always around :)

jonners (Jon) is also another good bet.

Marco.

[Spectral Morn]

PM him, dude - he's always around :)

jonners (Jon) is also another good bet.

Marco.

Just Pmed Hugo


Regards D S D L

[blake]

I tried a number of positions for the arm and it did make a difference in regard to lining up the cartridge using several alignment protractors I have. The position it is in at the minute allowed set up of the cart at point A and point B so that the stylus was nearly 100% parallel to the protractor lines.

I was hoping for some more info from more experienced Jelco owners if the position I have settled on is the optimum one or not.


Regards D S D L


Sorry, but within reason, this should not be the case as the Grand Wazoo alluded to earlier and it is not in my experience with my 750D. Small changes in positioning of the arm (provided the pivot to spindle remains the same which I'm assuming it is!) should not have any effect on cartridge alignment.

In my case they don't, both with a protractor printed using Conrad Hoffman's software and a Mint LP using the same arc and alignment null points.

[Ammonite Audio]

Sorry to be a bit late coming in here.

Neil, assuming that your armboard has been correctly cut, with the platter spindle to arm pivot distance set at 214mm, it does not matter whether you rotate the arm a bit in its collar - the essential alignment will always be the same. Next, align the cartridge roughly in the headshell so that the overhang (fore and aft alignment ) is set at 15mm - place the stylus tip carefully directly over the platter spindle and the cartridge should be located in the headshell so that the stylus tip sits 15mm beyond the spindle - move the cartridge forward or back as required. You should then be able to use a universal alignment gauge to tweak the lateral alignment of the cartridge in the headshell. I use a Clearaudio alignment gauge which makes all of this very easy.

Vinyl Engine is a good resource for this sort of thing. If you're unsure about alignment protractors, take a look at http://www.vinylengine.com/cartridge-alignment-protractors.shtml

I hope that helps and that I haven't been patronising!

[Spectral Morn]

Hi Hugo

No very helpful.

I was not aware of the 15 mm measurement.


Thank you.


Regards D S D L

[Ammonite Audio]

Setting the overhang that way means that, when you use your universal alignment protractor, you don't have to worry about aligning the protractor to the arm pivot (often there is an arrow printed on the protractor that you have to point to the arm pivot, which is a bit hit and miss, in my experience, hence why I use the Clearaudio alignment jig). You should find that getting the correct lateral alignment of the cartridge at the two null points is easy-peasy if your 214mm spindle to pivot distance and 15mm overhang settings are correct!

[Spectral Morn]

Interesting thread here about this issue and the mounting distance should it be 214 or 216.....

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1287657842&&&/Jelco-SA750-D-optimal-cartridge-aligneme

Anyone care to comment further ?


Regards D S D L

[DSJR]

Neil, do you have Hugo's "better-base?"

[Marco]

If not, he needs one tout-suite, as you can't get azimuth right without it! :)

Marco.

[Spectral Morn]

Yes I do.....:)

It was while fitting the longer grub screw and changing cart that this issue raised its head.


Regards D S D L

[DSJR]

Now, you lot are going to take me to task, but I used to set the inner null-point to 60mm from centre (optimised for LP records) and not worry too much about the outer point as tracking error on pivoted tonearms is wild however you do it (and not such a problem in any case IMO).

[blake]

Interesting thread here about this issue and the mounting distance should it be 214 or 216.....

http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1287657842&&&/Jelco-SA750-D-optimal-cartridge-aligneme

Anyone care to comment further ?


Regards D S D L

My username at Audiogon is Hdm so I was involved in the thread there, as well as a few at Audioasylum relating to the same matter.

I've attached a photo of my 103R on my 750D. Take everything I say with a grain of salt because 1) my 103R has been rebodied in an ebony wood body and 2) I don't use the stock Jelco headshell, instead using a custom ebony/carbon fibre headshell.

The jist of the matter is this: Jelco is quite possibly off on some of their numbers and if you want to achieve the 15mm Jelco spec'd overhang number it may well be impossible with certain cartridges if you are mounted at 214 mm (as I am). 216 mm is probably a more sensible mounting distance for this arm.

You will see in the photo how jammed I am with respect to the cartridge leads and pins in the headshell. This is with an overhang of 17.894 mm NOT the 15 spec'd by Jelco. I would not be able to achieve the 15 because the cartridge simply could not be moved that far back in the headshell. Other users, most using the stock Jelco headshell and cartridges like the 103/103R which are fairly deep from front to back (this is where the problem arises) have been unable to slide the cartridge back far enough to achieve that overhang. An extra 2 mm in the pivot to spindle would probably allow it.

Keep in mind that the Jelco #'s and alignment are proprietary (which is common with many tonearms); they don't conform to any of the traditional alignment protocols (Stevenson, Lofgren or Baerwald).

This has not been a big issue for me as I prefer Baerwald anyway (IMO it is in theory-and probably in practice-the most sensible alignment anway and Baerwald alignment with the traditional null points of 65.998 and 120.891 ends up providing me with a much lengthier overhang on the 750D which eliminates any mounting problems relating to Jelcos spec'd (much shorter) overhang. I end up with a different offset and the cartridge slightly twisted toward the spindle but the cantilever is aligned perfectly using (as I mentioned before) either Conrad Hoffman's arc protractor or the Mint using the same Baerwald numbers.

[Spectral Morn]

Thanks for that.....

Graham make it so easy. Spindle guide which sits over the centre spindle all you do is get the arm to rest on this point(there is a hole in the headshell it sits into) the arm comes with a jig which allows for two types of alignment...... Fit cart attach jig (two more guide holes in the headshell) adjust cart on headshell and Bobs your uncle.....simples.

SME also make it easy too.

This has never happened before in well over 25 years I have never had a problem setting up a cart on any arm before. The first cart was a Benz Gold (not mine so it had to go back) it aligned with no issue. The VDH Frog ......took me well over an hour of messing around. Trying different positions for the arm position....straight ahead, pointing in a bit pointing out a bit......urrrrrrrrr. Finally I got it right but this messing around put a doubt in my head that maybe the arm was not positioned right hence the question.



Regards D S D L

[Barry]

Hi Neil,

Suggest you look at: http://www.vinylengine.com/library/jelco/sa-750d.shtml .

According to http://www7a.biglobe.ne.jp/~yosh/armdata.htm, the salient details for the Jelco 750D are -

Arm length: 229mm
Overhang: 15mm
Offset: 19 degree

Null points: 69mm and 130mm.

If the arm is mounted the correct distance from the turntable centre (214mm), then it doesn't matter how the arm is set relative to the vertical axis of the horizontal plane passing through the arm base; as long as the arm can traverse the record playing arc, correct offset can always be achieved.

Don't get too hung-up on the theories of arm geometry and setup: whether it's done according to the theory of Baerwald and Lofgren or to that of Stevenson, it's all a compromise. Use any alignment protractor that has two null-points and you won't go far wrong. Third only to patent interconnect designs and record cleaning liquids, alignment protractors are the next product which offers an opportunity to bamboozle and impress through 'technobabble' the unwary by the less-than-scrupulous.

I should also respectively point out, that much of this information is readily available from the AoS Library. http://theartofsound.net/forum/showthread.php?t=3838

Regards

[blake]

Hi Neil,

Suggest you look at: http://www.vinylengine.com/library/jelco/sa-750d.shtml .

According to http://www7a.biglobe.ne.jp/~yosh/armdata.htm, the salient details for the Jelco 750D are -

Arm length: 229mm
Overhang: 15mm
Offset: 19 degree

Null points: 69mm and 130mm.

If the arm is mounted the correct distance from the turntable centre (214mm), then it doesn't matter how the arm is set relative to the vertical axis of the horizontal plane passing through the arm base; as long as the arm can traverse the record playing arc, correct offset can always be achieved.

Don't get too hung-up on the theories of arm geometry and setup: whether it's done according to the theory of Baerwald and Lofgren or to that of Stevenson, it's all a compromise. Use any alignment protractor that has two null-points and you won't go far wrong. Third only to patent interconnect designs and record cleaning liquids, alignment protractors are the next product which offers an opportunity to bamboozle and impress through 'technobabble' the unwary by the less-than-scrupulous.

I should also respectively point out, that much of this information is readily available from the AoS Library. http://theartofsound.net/forum/showthread.php?t=3838

Regards

I would suggest totally disregarding the numbers in your second link as they are a combination of specifications on the 750LB (which is a 12" arm) and the 750D which is a 9" arm. ie. the offset number of 19 is for the 750LB (offset for the 750D as spec'd by Jelco is 22 degrees) while the effective length number of 229 is for the 750D-effective length on the 750LB is quoted as 305 mm by Jelco.

Strange null points as far as I'm concerned. Not sure whether they would be different as spec'd by Jelco for the two arms but, either way, they are not null points that I'd be interested in aligning to.

[Barry]

Agree, re. offset angle of 22 degree:
http://theartofsound.net/forum/showthread.php?t=4275&page=2 (post 19).

Jelco themselves state the overhang to be 15mm. http://www.jelco-ichikawa.co.jp/e_tone_arm.htm

Null points seem to be 59.1mm/112.5mm. Not sure if this tallies with your null points.

Regards

[blake]

Agree, re. offset angle of 22 degree:
http://theartofsound.net/forum/showthread.php?t=4275&page=2 (post 19).

Jelco themselves state the overhang to be 15mm. http://www.jelco-ichikawa.co.jp/e_tone_arm.htm

Null points seem to be 59.1mm/112.5mm. Not sure if this tallies with your null points.

Regards


Odd that the null points are so different for the 9" and 12"!

I just ignore Jelco's numbers and align to the classic Baerwald null points of 65.998 and 120.891 (using Conrad Hoffman's software and a Mint LP which was a totally unnecessary purchase-live and learn) as I feel this is the best overall alignment. Results in a much lengthier overhang than the 15 spec'd by Jelco, just under 18 mm.

I agree with you about the "protractor business" and said so much in the "Avid Universal alignment guage" thread below.

[worrasf]

I can recommend the tractor made by Yip at MINT :)
(http://www.mintlp.com/best.htm)

This is the best alignment gauge I have used bar none.

It is custom made for each turntable depending on make and spindle-pivot distance and sets the correct overhang and offset angle and then in addition allows you to align the stylus (not the cartridge body) directly at the null points. In my case this involved "toeing in" the cartridge body slightly as shown in the attached images. It took me about 1 hour last night to fully align both my Astatic MF-100 and Nagaoka MP-11 Boron and the results are little short of stunning in terms of sound improvement compared to previous alignment which I was pretty sure was spot on.



Steve

[Spectral Morn]

Hi Steve


Chivas who's arm I bought has one of these and he has kindly offered to loan it to me. More than likely I will buy it and probably should have bought it from the start :doh:

Thanks for the photos and info my VDH Frog is sitting a bit like that at the minute.


Regards D S D L

[worrasf]

Hi Neil,

You wont be disappointed.

Obvious I know but ensure the arm centre-spindle distance is the same on your TT as it was on Chivas's otherwise the tractor wont work for you.

Steve

[Spectral Morn]

Hi Neil,

You wont be disappointed.

Obvious I know but ensure the arm centre-spindle distance is the same on your TT as it was on Chivas's otherwise the tractor wont work for you.

Steve

Its his armboard and arm on a Technics 1200 in this case but that should not make any difference (he has a 1210).

Regards D S D L

[Chivas]

Hi Neil

The protractor is in the post and should be with you by Wednesday, if the postman doesn't snow in since you're living quite far north... :-)

Let us know how you get on.

Chivas

[Spectral Morn]

Hi Neil

The protractor is in the post and should be with you by Wednesday, if the postman doesn't snow in since you're living quite far north... :-)

Let us know how you get on.

Chivas


Thank you Retief :)


Regards D S D L