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Mid-repair Pioneer PL-570 - advice wanted please

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Pat Santucci

New Member
A big thanks first to the forums; I've been able to get pretty far without asking a new question.

I have inherited a wood veneer PL-570. I'm trying to get automation to work; I can set it such that manual play works, but there are hitches in auto play.

The timing cam sticks at two places in its rotation. If I help it along a bit, I can get it through the cycle - the sticking places are at the end of the rotation to start, and the end of rotation to stop.

I started with the lubrication of the obvious places as noted in this thread:

http://audiokarma.org/forums/index.php?threads/repairing-pl-570.359517/

I also spent some quality time with the service manual to grasp what SHOULD happen, and decided I should have a go at the actual gear motor transmission, and also inspect for gear damage. I set out on that path today.

It felt so good at first. I got the transmission off, and it was very hard to move by hand; a quick spray of deoxit to clean and it spun freely. I re-lubed with grease and it was a little stiffer but still way easier than prior to the disassembly. All the gears are in fine shape, and as the pictures show, I don't seem to have the spline mount problem that has killed so many of this model; the drive gear is metal and firmly on the shaft.

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The main cam now stops and repeatedly clicks on the stop cycle, apparently hung on the parts the service manual (original page 34) calls levers B and C.

On the start cycle, it stalls near the apex of the cam track.

It looks like the main cam may be tilted relative to the plane of the mounting plate, but I've no idea how to test for it or correct it. Is there a way to be sure it is correctly fixed to the transmission shaft?

Any clues appreciated; I'd like to get this working and up for sale.
 
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Have you been observing the cam and linkage from the bottom, with the TT inverted? The linkages probably will not operate correctly unless the green side is up.

The gears should move smoothly and freely with the gear box separated from the motor. The gears should be lubricated, but lightly.

Start with a thin piece of plywood (or equivalent) with a small hole, at least 3+mm, and place one edge of the board in a vise or clamp it to a sturdy table. Set the gear box flush on the board with the gear shaft sticking thru the hole. Mount the cam wheel on the shaft with the set screw. Now view across/down the board at the gear shaft and cam as you rotate the cam while holding the gear box flat to the board. Hopefully you do not observe any wobble.

Use an on/off switch to connect the motor to 120VAC and see if the motor runs smoothly. Now repeat with the gear box attached.
 
If you photos are accessible from whatever devise you are using, try using the button for "upload a file" below the window you are typing in.
 
ghazzer said:
Have you been observing the cam and linkage from the bottom, with the TT inverted? The linkages probably will not operate correctly unless the green side is up.
Click to expand...

I've been testing in this position, holding the tone arm when needed to keep it off the stops: 20181120_185832.jpg 20181120_185838.jpg
I was confident fully inverted tests wouldn't tell me anything, but haven't come up with a way to manipulate the cam and see from the bottom.
I don't see a literal green side of any of the parts - does "green side up" mean more than the usual operating position? I'm sorry I don't recognize the term.

ghazzer said:
The gears should move smoothly and freely with the gear box separated from the motor. The gears should be lubricated, but lightly.
Click to expand...

The heavy silicone grease I used definitely reduced freedom of motion. What sort of lubricant should be used? I think this may be my biggest problem, with other symptoms due to sloppy re-installation of the gear motor.

I don't know how to disconnect and reconnect the wire linkages safely, so I cheated - I disconnected the lever to which one wire connected, thus: 20181118_163444.jpg
I couldn't do that for "wire A", and held the plate at an awkward angle to weasel the motor in and out of place. Anyone know how to remove and replace the wires without damage? I could be much more confident of mounting the motor properly if I could get the plate fully out or inverted.

ghazzer said:
Start with a thin piece of plywood (or equivalent) with a small hole, at least 3+mm, and place one edge of the board in a vise or clamp it to a sturdy table. Set the gear box flush on the board with the gear shaft sticking thru the hole. Mount the cam wheel on the shaft with the set screw. Now view across/down the board at the gear shaft and cam as you rotate the cam while holding the gear box flat to the board. Hopefully you do not observe any wobble.
Click to expand...
I now think I was wrong about the tilt and am just seeing pressure from a linkage. I'll hold on to the procedure, though - thanks!

ghazzer said:
Use an on/off switch to connect the motor to 120VAC and see if the motor runs smoothly. Now repeat with the gear box attached.
Click to expand...
Hesitant for the same reason as the mechanical force wires - I'm not sure I can disconnect and reconnect the gear motor wires to spec; it looks like they are crimped onto the binding posts, though it may just be solder over wrap - if that's the case, I can get it free.

Thanks.
 
This doesn't sound intuitive, but you will need a good pillow, some string, two chairs, a camera that takes video, and a helper.

Tie the two chairs together so that the edges are parallel and just far enough apart to support the TT base. Place the pillow on the floor between the two chairs and your head on the pillow so you can observe the mechanical linkages. Have your camera ready and have the helper hit the start button.

Now watch the video to see what the cam and the links do (or don't do). This should show you exactly where things are hanging up.

The wires from the gear motor are wire wrapped to the posts on the circuit card. You can carefully un-wrap them, then clean the posts and the wire, wrap them again and use solder to get a good connection.

I took lots of photos and made notes about all that I did. Hard to explain to someone else, but if you don't have a knack for this you need to find a tech who can work on a PL-570.

"Green side up" is an old joke about what you tell people who don't know how to lay sod. So, if the green side is not up, then the linkages may not have been installed correctly.
 
The project is over - I failed. Something I did when I got the gearbox out, lubricated it, and replaced it resulted in broken teeth and a box that seizes intermittently. In the process of discovering that, I lost a screw and a spring, on which the anti-skate mechanism depends. I also destroyed the stylus at some point; not sure which.

It's going up for auction, as-is, maybe good for parts.

Thank you for all your help. It did look possible for a while.
 
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