Pioneer PL-12 AC restoration questions

[klamsoss]

I picked this up for small money because it was in rough shape and I figured I could learn some stuff while restoring it and if I ran into a dead end or mucked something up, it wasn't a big loss.

It follows the popular, simple design of sprung chassis, belt driven by a synchronous AC motor. Nothing automatic here except the tonearm triggers the motor start. One little thing I thought was cool, but now realize is crap is that there are two little holes under the platter for oil. These lead to little string lined tubes that go to the motor bearings. Idea being that you don't have to disassemble the thing to oil the motor bearings, just a few drops and the string will wick it right to the bearing. Great idea, right?
WRONG
These decent but cheap tables were bought by decent but cheap people who probably didn't know what type of oil to use and weren't likely to spend extra dough on it IF they did. Consequently, in my case, they apparently used whatever bacon grease or crank case oil they had laying around.

Anyway.
The dustcover has a crack in it but is in half decent shape and I was able to glue the crack well enough. It's never going to win a beauty contest, but it works.

The vinyl veneer is peeling from some of the edges around the plinth and I've been trying to glue it back without ending up with wrinkles or a bunch of overhanging glue. I'm having mixed results. Garden variety super glue is what I tried first, and it doesn't bond well to wood. I tried some gorilla glue (not the foaming kind) which worked okay, but not great. Wood glue didn't work at all on top of the cyanoacrylate. Work in progress...

I pulled the bottom off to see what the guts looked like and found that the shredded foam of about half a couch had been crammed in there, along with some straw and other telltale signs of mice. The power cord and RCA leads had been chewed up but were easy fixes just by cutting the chewed parts off and soldering the good section of wire to the appropriate contacts. Tonearm wires were also chewed, but we'll get to that in a bit.

I've had excellent help from @AudioWizard getting the motor working properly. It's not terribly complicated to take apart. As always, make marks, take pictures, lay stuff out carefully so you can put it al back together properly...
1. You want to measure the distance from the top of the spindle pulley to the motor body before you remove it. It's not terribly difficult to get the height right again, but it will take some doing and the little set screw is not the easiest to tighten and loosen a bunch of times. The pulley has a slight bulge on which the belt will center. If that bulge isn't in the right height, the belt will rub on the guides of the speed selector fork.
2. Clean out all the old oil and crud but don't go wild with degreaser because those dumb little oil ports led to sponges around the motor bearings. Those sponges will hold the degreaser and break down the new oil.
Once you have it reasonably clean, I use a q-tip with some steel wool spun onto it, and put the q-tip in a cordless drill and use that to polish the bearings and clear off any patina. Just be extra careful to get any and all wisps of steel wool off before reassembly.
3. Once you have everything clean, don't use mineral oil (3 in one) on the motor spindle or bearings. Instead, use a light oil (I used ProGold bike chain oil). It won't gum up, and it will get where it needs to go without attracting dust and dirt. A drop or two is all you need.
4. as with most of these types of motors, reassemble it carefully and don't tighten anything more than finger tight until you verify that the armature and spindle rotate freely. Then work your way around tightening the screws, checking that rotation is free as you go.

The platter spindle was disgusting and had a little more play than I think it should. Honestly, if I was going to use this for focused listening, I would probably have had to replace it.
Don't lose the ball bearing, OR just plan on replacing it (I did, because I have bearings around from rebuilding bike parts). I did the same steel wool drill thing to polish the inside of the spindle bearing. 3 in one is probably okay there, but I used the bike oil again and then put a light film of grease on the upper portion of the spindle to try and take up some of the play. I put a drop of light oil on top of that, too, to thin it out slightly. The grease will stay put better than a liquid oil, and it took up some of the play in the bearing.

I got the belt on, and fiddled with the pully height until I got it right.

Now I need to replace the tonearm wires and fix the cueing arm height. See you in a few, on the next post. I'll have questions.

 

[klamsoss]

One of the corner supports was rattling around inside, which I had to glue back into place. This was clearly dropped at some point, which how the support broke loose. I was able to line everything back up sufficiently, though, without too much trouble.

To remove the chassis from the plinth, there are two nuts to undo under the platter. (Pointing to them in the pic) The springs for the suspension were in good shape but the foam damping material disintegrated pretty much as soon as I looked at it. I couldn't find any real recommendations for what to use other than "foam that isn't too stiff". I cut off the last triangle strip of a piece of sound damping foam panel and used pieces of that. Seems to work pretty well. It provides adequate damping without preventing suspension motion.
There were also only 3 rubber rings under the springs. I think their main purpose is probably to prevent the springs digging into the wood more than any meaningful decoupling or leveling. I could be wrong, though. To replace the missing one, I cut out a circle of bike tube rubber. It's about the right thickness.

I was able to adjust the tonearm rest to the proper height with the screw I'm pointing to in the picture. Look the mechanism over a bit and it makes sense.
What I'm puzzled by is how to replace whatever damping fluid is in the mechanism.

Any insight?

Also visible in that picture is the bottom of the tonearm column. Notice the lack of tonearm wires. That's the main thing I'm not sure how to do right now. There's no obvious way to remove the headshell collar at the end of the wand. I don't know how to get the plug that holds the pins out of the wand. Once I understand that, the plan would be to figure a way to attach the new wires to the old and pull them through. As yet, I haven't found any videos, photos or descriptions that address this particular tonearm.

 

[spark1]

Ideally you would disassemble and clean out the cueing mechanism (see schematic in service manual, available at vinylengine.com), then apply 300K-500K cst silicone fluid to the shaft. There is no reservoir...the fluid is very (very) gummy, and slows down the drop of the tonearm. For that series of tables, with their fairly heavy arms, I think 500K would be best.

If you want to avoid disassembly, you can simply use a small artists brush (fairly stiff) and some isopropyl alcohol to clean off the lower portion of the shaft and the spring (easily accessed from the underside), let dry, they use another small brush to apply fluid to the portion of the shaft you can access (with cueing down). This usually works just fine on these tables.

 

[klamsoss]

Thanks, @spark1 , I was able to get the cue mechanism to work properly without having to disassemble anything.

At this point, the thing I need to do is figure out how to do the tonearm rewire.

I don't understand how to get the collar off so I can undo whatever holds the pin plug in the arm tube. I was really hoping someone could weigh in on that aspect because I'm stumped. There should be plenty of folks who have experience with this table because the PL-12 variants were quite common.

 

[spark1]

I just looked at my PL12D (first decent TT I owned...bought new in 1974). It has a screw on the underside of the arm tube that holds the plug in place.

I've seen some arms with press-fitted plugs, and some with a spring-loaded pin that pops thru a hole in the tube when the plug is inserted.

If yours has a screw, It may have loctite on it. Heat may soften it enough to turn it.

I don't know about these tables, but I've seen some tubes with a ground attachment inside it. Make sure you know where/how the ground will ne attached before re-installing the plug

If you are going to solder to the plug pins, low heat (300F max, I would guess) and speed are critical. You can easily melt the core of the plug or do other damage. Maybe forceps or something similar as a heat sink for the pins?

 

[spark1]

I think you should veneer the base.

 

[klamsoss]

@spark1 how do I get the collar off to see if there is a pin or a screw?

I feel like an idiot here... I've taken apart a dozen other turntables and never had a problem DISassembling one...

 

[klamsoss]

HAHA, well I do have some nice 1.6mm 4 ply layered veneer type wood...

I probably won't put too much into it, though, because I know this will end up going somewhere other than my own collection. Plus I'm not a woodworker, really.

Now, my Thorens... that could use a new veneer. But really I would just build a custom plinth out of some exotic materials for that.

 

[spark1]

@spark1 how do I get the collar off to see if there is a pin or a screw?

I feel like an idiot here... I've taken apart a dozen other turntables and never had a problem DISassembling one...

On my 12D, it is "behind" the collar...that is, towards the pivot. The collar is part of the connector/socket assembly....similar to this, I think:

https://recordplayerz.com/products/...socket-connector-sme-type-record-player-parts

 

[klamsoss]

Unfortunately, my PL-12 has nothing visible. I looked up the picture you linked to, @spark1 , and proceeded to a few more to get familiar with the different kinds of collar setups. I didn't see anything that was exactly like mine.

There is one small hole in the collar, as pictured. I thought it might be for using some sort of implement to press a clip/button that might be hidden under the collar, and release the whole assembly. I can't see enough under the collar to see if there is such a button or clip, and have thus far been unsuccessful, using a very small allen wrench as a tool, poking around for whatever clip may or may not exist. I guess I will have to take the screws out of the pivot to remove the armtube and see if better access to all sides of the collar and armtube makes things more clear...

How difficult is it to reinstall the pivot screws and get everything set right? I feel like people fret over having to even look at their pivot assemblies, and disassembling them is sometimes treated like a task only a madman would attempt. But, I mean, I adjust bearings on my bike hubs, headsets, and bottom brackets without any major issue and, and I can't physically see the bearings on those as I tighten and adjust them... These are visible and appear to be fairly standard pivot screws that tighten up on the shaft of the arm base. There seem to be decent sized guides there, too... Am I being naïve thinking it shouldn't be a problem for someone reasonably mechanically inclined such as myself?

 

[klamsoss]

I know someone out there has dealt with this tonearm with this type of collar on it. I'm at a loss. All I can see though the tiny little hole is what appears to be the guide that provides the backstop for the collar. No amount of pressing or prodding on that guide results in anything coming loose. There is one other spot that looks like it might be a tiny clip or button, but it doesn't budge even slightly, either. If that's the "release mechanism" then it is certainly frozen. I'm about at the point where I'll just cut it off, but I doubt replacement collars for this tonearm are available... well... anywhere that wouldn't include the rest of the tonearm with it...

Anyone able to weigh in before I break out a hammer and a saw and end the life of this particular tonearm?

To reiterate: there is no screw for my to unscrew and remove the end plug. There is no visible button or clip, either. The tiny hole on the collar (pictured in my last post) does not provide any access to anything that I can tell. I've even tried just using a paper clip to poke as I move the collar around the armtube completely.

 

[klamsoss]

Well, here we are over a year later and my now-wife says 'do we really need all these broken turntables?'
Some have sat for over a year waiting for time/parts that might never materialize. I decided this pioneer would have to go since prospects were low of finally figuring out how to fix it. But let's check the bay one last time for the right tonearm tube.
Lo and behold!!
New arm tube in hand, I sat down last night and got it all together. The new arm tube had wires attached, which I left alone since the collar is apparently not removable. Pivot bearings weren't really difficult to wrangle at all.
BUT
As can be seen in the pictures, the tonearm wires come out near the auto off power switch. This is obviously going to create hum unless I figure out a way to shield it or move the wires.

So the question is do I get some braided metal sleeve like this thing was originally equipped with, thread the tonearm wires through, and call that good, or should I move the wire bracket over to the wood near where the wires come out of the pivot assembly and away from the switch?
If I go the braided mesh route, can anyone advise on what size to get? All the other turntables I have worked on either had mesh intact or used a different shielding system.

 

[stereofisher]

I would try running it without the mesh. Have done several rewires on Duals and my BSR 810. Had no hum on any of them. Do have a current Dual rewire with one channel out. Have done continuity checks that are good. Continuity is good and have a new BEST sled. So much fun. Good luck,

Eric