Marantz 6370Q - tonearm

[Aeon_MK]

Just being working on this crappy TT... the same issues as many other people indicated, loose tonearm bearings, slipping gears and crazy behaving auto-return. After thoroughly analyzing the operation cycle of the auto-return function I came to a conclusion the electronic control of this particular function is failing, exhibiting a stochastic behaviour. As I have never repaired a nuclear submarine or a 1970-ties computer, I have decided to disconnect the optical electronic gate entirely, remove the gears for the return function and focus on the lift part of the gearing, finding an optimal friction replacement for the gears to avoid slipping. Also disconnecting the Reject button entirely would be nice. What I get then is the same manual operation as with the Manual switch on, with the exception the platter would not start turning until the tonearm is moved from the parking position.
Should the electronically controlled lift fail again, I would replace it with a manual one, these can be easily obtained from Aliexpress or the likes.
The loose tonearm bearings is then another story.

The microswitches are all working and I cleaned everything with isopropanol. Not going to waste any India Pale Ale on a turntable, I use that to solve my other problems. I can see the cams, wheels, idlers, etc all moving in both directions when the motor direction changes back and forth so I don't think slipping is the problem. Worth double checking though, so thanks for the suggestion.

Just

 

[sa-9800]

Stochastic? I had to look it up but I think you nailed it!

As I mentioned, a single layer of friction tape on the toothed edges of the cams snugged things up on mine and now up and down cueing is working. Like you, I disabled the auto return, but I simply removed the little spring that keeps tension on the auto return mechanism. I also secured the arm that attaches to the spring so it stays out of the way and does not move the arm scholastically even in manual mode.

I thought the bearings were loose on mine, too, but it tracks well, maintains a consistent VTF and sounds good so I decided to leave well enough alone. I did remove the little rubber cup that is under the the tonearm damping adjustment screw and found the hole in the bottom was plugged with dried castor oil. I cleaned that, put it back in and added a few drops of Tri-Flow. Arm motion seems a little smoother, but wasn't really a problem before cleaning.

I like the turntable as is, now, but am also considering putting a different tonearm on it.

Good luck and stay safe over there.