Tonearm for Technics SP-15

The ground pin is the same size an RCA center pin.  Easy peasy. 

Most of the arms I see, if not obviously broken (shattered/missing balls), will typically present with at east one pitted ball in a bearing. These can seem to work fine until that pit works its way around to the running surface of the race or pivot, at which point the bearing is ’loose’ with play. It’s also typical for there to be fine detritus in the bearing increasing friction.

Half the time on seemingly good arms I find indentations from the balls in the pivot surface. These surfaces need to be re-ground and polished out for best performance, or the arm will tend to have resting positions when the balls rotate around to fit in the indentations. Usually because of the detritus in the bearing the friction is high enough that this condition isn’t obvious from obersvation.

The silicon nitride balls I use have better roundness and surface finish and a lower friction coefficient than the original rubies. This makes the outstanding bearings in these arms just a bit better.

With these arms, even in poor condition relative to their potential, the performance is beyond most contemporaries. This is to say that people don’t realize they’re leaving performance on the table. If your EPA-100 is nearly impossible to get to hold balance and moves around on air currents in a seemingly completely still room, then there’s an excellent chance it’s still in great shape. If not, it could be a lot better.

EDIT: Nearly forgot - on all of them with original wiring the insulation has reacted with the copper causing a good deal of corrosion and fragility.

@chakster The 100MK2, while similar, has a noteable difference.  The bearing pivots on the 100 are spring-loaded and hard-chromed.  The 100MK2 uses the same pivots as the B500 which are not hard-chromed nor spring-loaded.  The spring-loading doesn't serve any practical purpose.  The pivots can be surfaced and polished to perform at the level that can be achieved with the EPA-100 but aren't quite there as-deliverd.  They're also more prone to corrosion. 

A bit more than double the VTA range which is nice.  CW and AS are the same, and on the MK2 it's easier to tailor cables as they're RCA rather than DIN.  Wtih some TLC they very nicely.

I believe the Japanese generally prefer the original, and it certainly as a more traditional feel to it.  My daily driver is a B500 with surfaced and polished pivots and Si3N4 balls for 100-level performance with the conveniend of detachable armwands.  Once used to it, the ergonmics of the 100MK2/B500 is really nice. 

Don't forget the EPA-A505. 

Hi @lewm 

For that mod I'd recommend machining a new base pillar cap to be able to fit a cable retainer.  You'd either need to solder the IC at the bottom of the base pillar, or run thin-guage wire the whole way through from the connection PCB in the base.  The latter may not be ideal for a good many MM carts as the cable capacitance of such a set up would be rather high.  

The mod I'm working on is a pillar cap so I can terminate mini-xlr, as I run balanced.  That's more of a personal project as 1) I don't think many people would be interested in it and 2) it's something intersting that gives me an excuse to put the lathe and mill in the garage to use. 

I switched from Triplanar to Technics.