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Pioneer PL-540 - Question re: auto return

sinnerboy

sinnerboy

Well-Known Member
Diagnosing the auto return issues with my PL-540. Before I get to the problem, kudos to me for soldering the tonearm wires back to the harness, two had broken off during my working on the return mechanism. First stripping the tiny wires was a delicate procedure, but when it came to soldering them back in place, my 64 yr.old eyes had a hard time seeing what I was doing. But I succeeded before I executed my plans to appeal to someone here to do the job for me. But that's not what I'm here to talk about.
Symptoms are when the auto-return kicks in, the tonearm moves back to pedestal, then the auto-return mechanism gear re-engages, turning the motor back on and the tonearm just sits off the pedestal while the auto-return mechanism iterates on and off.
Everything else is working, auto-return kicks in at the appropriate point in playback, arm moves to arm rest, micro-switch is deactivated, motor turns off. Then, it appears that the momentum of the table rotating engages the auto-return mechanism again, closing the micro-switch plunger, starting the motor, starting the whole process over.
I'm thinking the trigger on the auto-return gear is re-engaging when it shouldn't. Not sure how to fix this. This pic is after it has gone thru the return process, you can see the trigger still positioned to catch the drive gear lobe as it spins by. I can see how it's supposed to work, the trigger has a lobe at the front end that, as the drive lobe engages, it pushes the trigger out of position. Well, that isn't happening. I did clean and lube the trigger, not sure what my next step is. Any suggestions?
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Those two plates are the starting plate and the signal plate; that mechanism is common on most auto-return Pioneer turntables of the 70's and 80's. The problem typically is that the plates require a drop of lube between them so that they can move freely back and forth as the engage and then reset. Be careful not to over-lube. I use sewing machine oil but gun oil will also work quite well.

If there is old lube on the plates remove it before lubing.
 
Also on most models, once you've lubed the plates, you should rotate the center spindle until the mechanical assembly re-sets before reassembling the unit.
 
beej said:
Those two plates are the starting plate and the signal plate; that mechanism is common on most auto-return Pioneer turntables of the 70's and 80's. The problem typically is that the plates require a drop of lube between them so that they can move freely back and forth as the engage and then reset. Be careful not to over-lube. I use sewing machine oil but gun oil will also work quite well.

If there is old lube on the plates remove it before lubing.
Click to expand...

I think part of the problem is I used white lithium grease, which is probably too thick. I'll clean and use some machine oil. Thanks.

beej said:
Also on most models, once you've lubed the plates, you should rotate the center spindle until the mechanical assembly re-sets before reassembling the unit.
Click to expand...

Yeah, I figured that out when I had the gear off, i.e. why is there a track on the bottom of the gear....
Thanks for replying, I hope this works.
 
Keep us posted. Yeah that lithium grease is a bit viscous for those plates.
 
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