Pioneer PL-530 Auto Return Thump?

[JamVal]

I've had a Pioneer PL-530 for about a year and a half, and it has always made a 'thump, thump, thump' noise as the stylus enters the inner run-out groove area before the auto-return mechanism lifts the arm and returns it to the arm rest. I assume it's due to the auto-return mechanism.

But, I have a few albums where the last song is recorded into the area where the 'thumping' starts. It is annoying to listen to that 'thump, thump, thump' towards the end of the last track being played.

Is this normal behavior for the PL-530, or does something in the auto-return mechanism need to be adjusted. The arm returns to the rest as it should. As I said, it's behaved like this for the time I've owned it.

 

[Doskiez]

I am sure it is a little different but the auto return on my PL518 is noisy as well. Mine is triggered by the arm speed so you might be able to adjust it at the tonearm where that part of the mechanism connects. It has been a while since I have had that table apart so I don't remember exactly what that end of the mechanism looked like.

 

[JamVal]

I think the PL-530 auto return works like this:
Under the platter, there is a pivot plate that gets pushed towards the spindle by the tone arm mechanism as the tonearm moves close to the inner run out groove. There is a pin that protrudes down from the bottom of the platter close to the spindle hole. When the pivot plate travels into the path of that pin, the pin hits the pivot plate moving it back to where it came from and causes the tonearm to return.

I might be wrong, but I think the noise is from that pin hitting the pivot plate 2 or 3 times on records that have last track grooves very close to the center before it is able to push the pivot plate back. It is a 'thump, thump, thump' when the system is on, but just a faint click with the amp turned off. I don't hear the thumping on LP's with a normal to wide inner run-out groove. I can't verify my assumption because you can't see what's going on with the platter on. But the service manual describes that the pin 'brushes' the pivot plate aside with each rotation until stylus movement exceeds 3mm per record rotation, at which point it fully engages the return of the tonearm.

One known issue with my PL-530 that is common to them, is the cushioning in the 4 feet is shot, virtually no vibration isolation. It's not a problem for my normal listening as the turntable sits on a heavy equipment cabinet, which is setting on a concrete slab floor. I can jump up and down right next to the cabinet while an LP is playing with no effect whatsoever. But when that auto-return mechanism starts to engage with the platter pin 'brushing' against the pivot plate, I think the clicking gets amplified to a 'thump' due to no vibration isolation.

A few things I might try:
1. Lubricate the pivot point of the pivot plate to ensure there is minimal resistance as the platter pin brushes by .
2. Replace the feet, or isolate them.
3. Apply some damping material to the underside of the platter.

 

[boreas]

I think the PL-530 auto return works like this:
Under the platter, there is a pivot plate that gets pushed towards the spindle by the tone arm mechanism as the tonearm moves close to the inner run out groove. There is a pin that protrudes down from the bottom of the platter close to the spindle hole. When the pivot plate travels into the path of that pin, the pin hits the pivot plate moving it back to where it came from and causes the tonearm to return.

I might be wrong, but I think the noise is from that pin hitting the pivot plate 2 or 3 times on records that have last track grooves very close to the center before it is able to push the pivot plate back. It is a 'thump, thump, thump' when the system is on, but just a faint click with the amp turned off. I don't hear the thumping on LP's with a normal to wide inner run-out groove. I can't verify my assumption because you can't see what's going on with the platter on. But the service manual describes that the pin 'brushes' the pivot plate aside with each rotation until stylus movement exceeds 3mm per record rotation, at which point it fully engages the return of the tonearm.

One known issue with my PL-530 that is common to them, is the cushioning in the 4 feet is shot, virtually no vibration isolation. It's not a problem for my normal listening as the turntable sits on a heavy equipment cabinet, which is setting on a concrete slab floor. I can jump up and down right next to the cabinet while an LP is playing with no effect whatsoever. But when that auto-return mechanism starts to engage with the platter pin 'brushing' against the pivot plate, I think the clicking gets amplified to a 'thump' due to no vibration isolation.

A few things I might try:
1. Lubricate the pivot point of the pivot plate to ensure there is minimal resistance as the platter pin brushes by .
2. Replace the feet, or isolate them.
3. Apply some damping material to the underside of the platter.

You have the cause right but not the cure. The cure is to adjust the return point in small increments until the thumping stops. But here's where it gets tricky. Since the PL-530 is fully automatic and since the adjustment fro the lift point is the same screw as the set-down point (adjusting one simultaneously adjusts the other), you might find that the needle drops some distance into the playing surface after you've eliminated the thump. This is down to the fact that some records are recorded to within 1/4" or so of the label. If that turns out to be the case, readjust the tonearm so that the stylus just misses the recorded surface. You'll still end up with a thump on some records but the vast majority will be thump-free.

John

 

[JamVal]

Thanks John. If that takes care of the problem it won't bother me that the starting auto set down point is off, because I usually have the record size selector in the manual position and manually move the tonearm over the lead in groves.

Out of curiosity I did a more detailed read of the service manual. Page 43 shows how to set the starting tonearm lowering position as you pointed out, but starting on page 44 there is a procedure for 2 more adjustments; auto return position and auto return detection position. Not sure what the difference is between return and detection positions.

Auto return position requires setting the deck in play mode, disconnecting the ac plug, move tone arm to the center, then put it back on the arm rest, rotate the platter one revolution in reverse, remove the platter, adjust the plate stopper to 1 - 1.5mm from the pivot plate H. This looks easy enough from the top with the platter removed and I don't think this is causing the thump.

Auto return detection position is more involved. Move the tonearm back towards the center, stopping at a point where the stylus is 64mm from the spindle. At this point an adjustment screw running through plate F should be in contact with plate G. Looks like this needs to be done from the bottom, I can't see plates F and G from the top.

 

[boreas]

Okay, I gave you a bit of a bum steer. The return mechanism for the PL-530 isn't the type I was thinking of. But I think I can help you anyway. In the diagram below there is what I believe To be a misprint. Plate G isn't shown in Fig. 21-b but Plates H and F are. Those are the ones we need to concentrate on.

What we want to achieve is to adjust things so that Plate H strikes the pin on the platter a little later so that contact is made just as the stylus enters the dead wax. when this happens the arm begins to move to the center more rapidly causing Plate H to strike the pin more forcefully, tripping the mechanism on initial contact with the pin. You're going to accomplish this by gradually backing off the "Adjust screw" at the point where Plates F and H meet.

I don't have a PL-530 to look at here but I think you're right and that the Adjust screw is accessed from underneath. And I think that Plate F is attached to and moves with the tonearm.




John

 

[JamVal]

Thanks John, that makes sense, backing off on the adjustment screw will cause the tip of plate H to be further away from the platter pin. This looks like it could be a trial by trial effort.

I saw a thread recently where a member made a fixture to hold the table with the bottom off. That allowed him to make incremental adjustments without constantly flipping the table over and back. One of those would come in handy for this.

 

[boreas]

I saw a thread recently where a member made a fixture to hold the table with the bottom off. That allowed him to make incremental adjustments without constantly flipping the table over and back. One of those would come in handy for this.

Yes, that would be a big help.

John