Jelco tonearm anti-skate design on the current tonearm models SA-250ST, SA-250, SA-750 is simple, yet quite precise. In the “zero” position, the spring wire does not make contact with the rotating arm pivot, so there should be no anti skate force normally applied.
However, the OEM arm made for AR, Revolver, Mission and others may not have been exactly the same and it’s possible that there might be a slight anti-skate compensation applied near the inner groove area if it isn’t able to fully disengage itself. Some amount of anti-skate compensation would be expected by the arm manufacturer, so perhaps less precise design was used (cost reduction) that applied correct pressure within the normal range, but didn’t fully disengage at the extreme end of the arm travel.
Another thing to remember is that the arm/turntable need to be perfectly level, otherwise there may be some gravitational pull due to the bearings not being in an equal horizontal plane.
Additional Notes (OEM tonearms)
Rather than trying to alter spring tensions and alignments, that the customer try to determine if the turntable is level first (not the plinth, but the platter and arm board), and then see if the arm drift occurs only for the last half of the record area, or over the entire range from the arm rest all the way to the spindle. If it’s only during the inner half of the record, then it would be the equivalent of about 1/4 gram anti-skate force. If it drifts back all the way to the arm rest, but barely, then it would be the equivalent of 1/2 gram. I would then suggest just setting the anti-skate dial to a bit less than the tracking force to allow for the discrepancy. It’s always better to have a bit less anti-skate force applied than too much.
Posted in: Jelco Tonearms and Accessories