I owned a Rabco ST-4 and still have an HK/Rabco ST-8, which has worked perfectly since 1978. I'd be a leary about buying an ST-4 sight unseen. That design was a mechanical mess. The ST-7 and ST-8 were better and, as Willster's friend said, can often be rehabilitated with replacement rubber belts and an O-ring for the dried out rubber tire that supports and moves the arm. BTW, I have the ST-8 service manual if you go that route and need a copy.
The really hard part of a Rabco rehab is finding a decent armwand if the original is missing, damaged or needs a rewire (nightmare job). HK/Rabco armwands in good shape are getting difficult to find.
Will these compare with an ET or an MG-1 on a decent rig? No. The HK/Rabco tables are too resonant and rumbly for anything like "high end" sound, and these ills would be difficult to tweak away. But it might be a fun project that could produce worthwhile, entry-level sound for very little cost. It's all a matter of your goals and budget.
The really hard part of a Rabco rehab is finding a decent armwand if the original is missing, damaged or needs a rewire (nightmare job). HK/Rabco armwands in good shape are getting difficult to find.
Will these compare with an ET or an MG-1 on a decent rig? No. The HK/Rabco tables are too resonant and rumbly for anything like "high end" sound, and these ills would be difficult to tweak away. But it might be a fun project that could produce worthwhile, entry-level sound for very little cost. It's all a matter of your goals and budget.