RP-190 Tone arm

While rebuilding an RCA RP-190 changer I had trouble with the arm tracing the record. I used a Pickering cartridge tracking at 6.0 grams. I could clearly see the cantilever bending while trying to drag the arm accross the record causing some mis-tracking. So I tried an experiment. I removed the collar from the tonearm mount and replaced it with some small ball bearings I extracted from a bearing assembly and the difference was amazing. The arm dutifully traced the record without resistance to latteral movement and hence the mis-tracking ceased also. I am thinking about reducing the tracking force as the cart tracks as low as 3.0 grams. I am sure I am not the only one who tried to put a magnetic cart in one of these changers and I would be interested in any other ideas or comments. For anyone rebuilding these units however, this is a procedure that works.

Those do have a rather high pivot friction.

Watch out for one other thing you can't fix by reducing friction. The tonearm has to overcome the detent brake on the change cycle drive wheel to start the change cycle. If you reduce friction here, the change cycle repeats without allowing the record to play.

Thanks for the reply. If it is there I've not seen it or identified it as such. I know I used a grease for the change cycle drive shaft, as per Paul Childress, to keep the drive from turning past the detent after the cycle has finished. It has since been working great, even on the EP records.

The grease itself provides too much friction for light-tracking pickups.

I have rebuilt several dozen of these and use
the Pickering or Ortofon
OMPro. I can track at 3.5 grams perfectly.
You must polish the plates and all parts of the arm shaft and swivel
to a mirror finish. I use
various grades of rubbing compounds.
Sometimes the tonearm wire has stiffened with age
and must be replaced also.
You cannot use the original cartridge mounting holes, as the magnetic
cartridge needs to be
all the way forward for
proper tracking angle.
These magnetic carts
are heavier than the original crystal cart so
you have to shorten the
counterbalance spring
to achieve the desired 3.5-4 grams.
Once all this is done properly, pivot friction is minimal and you willhave no problems
with stylus deflection or mistracking at the lower weight.
The tripping mech does require at least 3 grams.
These came from the factory set to 5 grams with the original crystal.
Having the problems you describe at 7 grams
tells me the above procedures
have not been done

I didn't do the polishing you described and to tell you the truth I never gave it a thought. It certainly does make sense. The obvious eluded me. I'll put her back on the bench and give it a go. Thanks for the heads up. The tonearm wires have been replaced as have the idler wheel. The cycle drive wheel was of the thick rubber style and just needed cleaned up.

Be sure you clean and polish what I call the
swivel, held in place by a
c clip underneath the
arm thrust plates.
The grime that collects
in this is what causes most of the friction.