RE: Rabco SL-8E

Used a Rabco for well over a decade still have it lying about, as a matter of fact. ought a second for parts and modification, but never got around to it, having moved on to an ET II.

Unless you are running an air bearing type arm and even if so, all linear tracking arms exhibit the issues mentioned to a certain extent. Air bearing arms need to go slightly off track in order for the pressure to correct and align the arm tangentially. That's why higher pressures and closer tolerances make a large sonic difference. Uncaptured air bearings, like the Dennesen can exhibit even greater changes in tolerance concerning tangentiality.

Even arms like the fabled Goldmund, which used electronics to move the arm did not compensate for out of centered LP's and would not move outwards.

The Rabco assumed, like many others, a perfectly centered LP. The out of tangent rate was monitored mechanically by two gold plated wires. Contact with the first wire would turn on the motor which would pull the arm along the track towards the record center. You can easily adjust the gold plated wire to insure a more constant tangent. The second wire was for the lift motor actuation at the end of an LP. The greater movement at the run out groove would enable contact with this wire and turn on the lift motor.

While sounding a bit cumbersome, the system worked well. The issue of being out of tangent, while not totally eliminated, is far less than the end groove deviations with any pivoted arm, even if it be any of the current superarms. After all, any pivoted arm is truly and properly aligned, at best, at only two points in its arc across the LP.

The Rabco was also the subject of modification by David Shreve, if memory serves me right. I ran into the man at Christopher Hansen's salon in Rodeo Drive decades ago as he was checking out the Goldmund table and arm.

Had an interesting conversation with him as we listened to the demo. Among other things Shreve rebuilt the arm, rewired it and used a piece of balsa to manufacture the actual arm. I believe he reworked the counterweight and did other modifications to the arm improving its overall performance.

The chief issue was the use of a battery to power the arm. Seemed that on my arm it always died in the middle of play, and then of course the lift motor would not work either......I bought all the parts to build an AC power supply, never got around to it, though.

Because of the relative age of the Rabco, the chief issue today would be the quality of the wiring and it was an issue even back then. Bearings could be improved too (Come to think of it, Shreve did a mod on the bearings also). Getting rid of the large amount of ferrous material would certainly help some.

Again, YMMV

Stu

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