Jelco SA750 D optimal cartridge alignement


I have just installed a Jelco SA750 D with an AT 150mlx on my technics SL-1210 using the TimeStep armboard. Spindle-Arm centre distance is 214 mm.
The mounting template supplied shows the stylus tip about 2mm behind the front of the headshell yet it is impossible to set any of the various null points if the stylus is put here. I have settled on the Jelco null points of 59 & 112.5 although vinylengine also lists different null points for Stevenson, Baerwald and Lofgren B. Is there any received wisdom that one is "better" than the other and why does the stylus point not match the OEM mounting template even when using the Jelco default null points?

I have a 750D on a Gyrodec.

There has been considerable discussion at the Vinyl Asylum about the mounting distance of 214 mm on the 750D not being "right". At 214 it's quite possible that you might not be able to achieve proper alignment with many cartridges using Jelco's overhang # of 15mm (think that's what it is if I remember it correctly). A "better" mounting distance would probably be in the 216 mm area.

In any event I wanted to align using Lofgren A (also known as Baerwald) anyway. My overhang is much closer to 18 mm than 15 and I prefer the Baerwald null points. Bear in mind that if you do opt for a different alignment than Jelco's that you will end up with the cartridge not being square in the headshell as the offset angle will change.

If you want to experiment a bit, I'd recommend using Conrad Hoffman's software to generate an arc protractor. Get the overhang dead on and you will essentially be aligned. Print the protractor on high quality photo paper, spend $2 to have it laminated and then tape it to a record. I ended up recently purchasing a Mint LP and it simply confirmed that the Hoffman Arc Protractor was dead on.

I'd also recommend you purchase an illuminated 20x loupe off E-bay to use to align (they're about $15 or $20). It will allow you to get a very precise alignment.
Thanks - yes it seems quite an "issue"
FWIW I spent a few hours this evening experimenting with various null points - Stevenson, Baerwald, Lofgren B and I could not get any to line up at both inner and outer! However, the Jelco OEM null points of 59.063 & 112.507 do line up and what's more in this position the stylus tip is exactly aligned with the Jelco arm template position! I'm committed to a distance of 214 mm as that's where my (very expensive) armboard has put it. Looking at the distortion curves on vinylengine for all 4 settings the OEM ones look an OK compromise to me.
So it certainly looks like 214 mm is not the best mounting distance for this arm.
I'm mounted at 214 mm as well. The issue with many cartridges at that mounting distance is not having enough room in the headshell slots to move the cartridge back to achieve alignment with the 15 mm overhang specified by Jelco. I simply would not be able to do it.

I'm aligned perfectly (with the cantilever, not the cartridge body) using Baerwald and the traditional Baerwald null points of 65.998 and 120.891 and an overhang of 17.894 but if viewed from above in the headshell, the body of my cartridge is skewed slightly inward toward the spindle reflecting the change in offset from the Jelco specified 22 degrees to 23.764.

Not a big deal, and my preference would be for the alignment that I have anyway, but Jelco's numbers can cause problems for many, particularly those with fairly "deep" cartridges from front to back.

The beauty of Conrad's software is that you can (fairly easily) generate an alternative alignment protractor or protractors that will work and allow you to achieve proper alignment.
According to the alignment calculator on VinylEngine, the Jelco recommended geometry puts the null points about an inch in from the outer adge and then just before the inner runout grooves. There are other geometries that will work with minimum changes.

I have a SA-750D and am looking at options. Some require a different headshell. The headshell for the Micro Seiki MA-505 (or compatible) would work well since there are no front or side lips to limit the cartridge position. I tried using that headshell and it works fine on the SA750D.
I have just ordered a custom MintLP tractor from Yip at specifically for 214 mm and am assured I can align my AT 150 MLX to Baerwald so am hopeful. FWIW this morning I installed my Astatic MF-100 in the Jelco - again to OEM null points and I am delighted with the result - tracks band 3 of HFN test disc no worries and sounding stunning.
I was at the center if the controversy over at AA (my username there is vynyltap).

I stand by my finding that the Jelco spec'd effective length is just flat wrong. Why they don't correct it is beyond me. For what it's worth, the AT-150mlx will align just fine as mounted via Baerwald.