Yamaha PX-3, need some help

Fishead

Fishead

Gone fishin' Steada just wishin'
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This just started happening, not sure why and I really haven't played this table much lately. The arm, as it is dropping to the lead-in groove, starts to drift toward the spindle and makes contact with the record about 1/4 to 1/2 inch into the first track. Doesn't happen every time, but more often than not. Any ideas? Anyone encountered this issue before? I've had the table since it was new, bought it in 1982. I have gone through it and cleaned the large belt, made sure everything else is as it should be, new belts (the three small ones). The only thing I haven't played with is the arm and the arm base. I have a feeling I'm going to be playing with it fairly soon though. Thanks for any insights......
 
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Fishead said:
This just started happening, not sure why and I really haven't played this table much lately. The arm, as it is dropping to the lead-in groove, starts to drift toward the spindle and makes contact with the record about 1/4 to 1/2 inch into the first track. Doesn't happen every time, but more often than not. Any ideas? Anyone encountered this issue before? I've had the table since it was new, bought it in 1982. I have gone through it and cleaned the large belt, made sure everything else is as it should be, new belts (the three small ones). The only thing I haven't played with is the arm and the arm base. I have a feeling I'm going to be playing with it fairly soon though. Thanks for any insights......
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The transport belts and its assembly needs cleaning...over time the lube gets hardened and the belts need changing. Down load service manual and other information from VINYLENGINE website...from the library go to Yamaha PX-3 and down load everything......this will help you to understand.
Also if you change all the electrolytic capacitors with high quality ones, this will bring back the system to its original state. After more than 35 years these capacitors are almost dead!
 
So you are saying that the problem is not with the arm mechanism but with the belts and assembley? I went over that about 2 years ago and changed the belts. I did not mess with the caps however. I was thinking it was more to do with the arm assembly itself because I have not done anything with that. I have already gotten the service manual but have not delved into the arm assembly, but appreciate your suggestion about the caps. Anyone else have experience with this and if so, what might be your thoughts?
 
When you hit the down button, I expect the arm and the arm carriage is stationary with the stylus a directly over the lead in groove(?).
Doe the tonearm carriage start moving when the arm is released? What is the arm itself doing; does it stay centered to the carriage or is it swiveling in the carriage towards the center of the disc?
If the arm, when released, wants to move off it's center position and the servo is functioning properly, the control logic will move the carriage in that direction, expecting it to straighten the arm (which it "thinks" is in the record groove; if it were, that would be appropriate)
The arm should fall without drifting to either side; when it reaches the groove, the servo-logic commands the tonearm carriage (tonearm assy) to move to restore tangency as the needle moves in the groove.
This is not a belt problem.

There is a V shaped part in the fulcrum area of the arm that engages a tit on the arm when the arm gets raised. It moves the arm to it's centered position until the down command occurs. When the arm is up, it should resist deflection although with a little force it can be skewed.
When the arm is released and in the down position, it should be as free as any good tonearm. In this condition, if it drifts, that is the cause and the servo is just following logic.
You can do a lot of inquiry by moving the arm out midway between park and the edge of the platter and releasing it there. It's not good to have the motor run without the platter in place so I don't recommend that.


waiting for information back
 
I notice that when I hit the down button, the carriage does begin to move a bit to the left (center of record). The arm appears to be moving to stay centered to the carriage so that is an indicator that the carriage is perhaps the issue? I just moved the arm midway between park and the edge of the platter and let it down.....the carriage moves slightly to the left (towards edge of record) and it causes the tonearm to appear to be drifting. I think it is as you say, the carriage is moving as the tonearm descends making it look like the tonearm is drifting but it is actually trying to stay centered to the carriage. What's the fix for this? Thank you by the way pfcs49. Confirms my suspicion that it is not the belts.....
 
as I said, in the up position the arm should be centered and resist deflection. Does it?

Try releasing it in the space before it reaches the platter. If the assy moves, try grabbing the head shell and hold it stationary. The servo should then bring the carriage to a position that puts the arm straight out the fulcrum assy; any deviation is pretty visible if you watch the spaces between the arm carrier and the arm itself; the gaps should all be parallel. Then if you move the headship 1/4 inch inward, the servo should copy this motion.
This demonstrates that the servo is working correctly.

You need to discern whether the servo is "crazy" or the arm is "biased" (left-leaning, wants to move away from the normal "center" when it is allowed to float)
I hope the mods don't think this is a political discussion:)
 
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Sorry, I'm not understanding what you mean by resist deletion.....? However, I tried the operation you suggest and the carriage IS copying the motion of the arm as I grabbed it as you said and any movement, either in or out, causes the carriage to copy this motion. I tried it towards both left and right positions to satisfy any political incorrectness....:bigok:

I believe, from what you are saying, that the arm is indeed biased and that the carriage is just moving to accommodate the arm as it drops and starts to drift inward.....what could the problem be?
 
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Fixed that (thank you autocorrect) deflection
When the arm is up it should self-center and resist being moved away from that position.
If the self centering function isn't working, it can be anywhere in it's arc of movement it has, even when up or parked.
And, if it isn't centered when up, the servo will try to correct for this as it's lowering (I think:) ) and the carriage will move in the direction of it's deflection.

Sounds like the servo functions normally.
When it finally gets in the groove of a record, I assume it tracks it and stays tangential to it, i.e.: straight out from the carriage, 90* to the tracks it moves on, following the inward travel of the groove while staying tangential to it.

If it's parking straight out/arm resists being moved from it's center position, then probably that linkage isn't a problem.
If you cue it into the gap before the platter and hold it, it goes to tangent position and stays unless you move the head shell left or right, correct?
If yes, then what happens if you let go of it? does the arm want to move inwards and the servo "chases" it (as it should)
If so, what is the causing the force that makes the arm move/twist on its gimbals? Is the turntable grossly out of level? Is the force so small that you can counter it by lifting the other side of the turntable to counter it? Can you look with a small light into the fulcrum area for some small debris (like a down feather) that got in there and is causing a force, almost like anti-skate force on a conventional arm?

Time for bed!
 
The arm does self-center and does resist moving from that position so no problem there.

It indeed does track when it hits the groove and stays tangential.

Yes, when cued to the gap before the platter and held it goes to tangent position and stays unless I move the arm left or right, in which case the carriage follows it.

When I let go of it, it seems to stay in that position with no further movement.

Table is dead-on level. First thing I checked but it could not have been out as it hasn't been moved and I've had it level since I put it on this shelf.

I will look for an obstruction. Thank you again and I'm about ready to hit the hay too....tomorrow is another day and I'll have more of a look at it.
 
Fishead said:
So you are saying that the problem is not with the arm mechanism but with the belts and assembley? I went over that about 2 years ago and changed the belts. I did not mess with the caps however. I was thinking it was more to do with the arm assembly itself because I have not done anything with that. I have already gotten the service manual but have not delved into the arm assembly, but appreciate your suggestion about the caps. Anyone else have experience with this and if so, what might be your thoughts?
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Since you have not fiddled with the original arm assembly pivots and other adjustments....the motor control circuit needs re-adjustments. This same thing happened with my Pioneer and Technics linear tracking turn table. The LED photo sensor voltages where 20-30% out of specifications. Also the tone arm drive motor's field magnets had become weak over 35 years........(toy train motor magnets often get magnetized to full strength as it is a common problem and a motor magnetizing kit is available for the same...lots of people re-energize them!)
I had had thoroughly checked the tone arm azimuths and it was absolutely perpendicular to the platter....
I had replaced all the capacitors with WIMA/VISHAY brand....also good amount of carbon resistors were replaced with 1% tolerance Metal film resistor.
The tone arm drive motor was replaced by new one from Al-Express with very high sensitivity and low drive current (motor voltage was the same as original)
The adjustment variable resistor pot was replaced by multi-turn Bournes resistor (it has 20 turns for the same range).
I went about accurately setting the voltage with a DMM to second decimal point and now the turntable was working like a beauty!!
The test LP was used for all tracking checks....all my problems just disappeared!!! ( I am using a SHIBATA stylus)

When ever the tone arm moves forward when lowering it at the starting point........the adjustment of the tracking sensor is out and it will give command to the motor to move it forward.....if the center point voltage of the tone arm is correct to even 10% of the specified voltages still the system will work perfectly....

Any vintage linear tracking turn table will suffer parts deterioration over a period of 35 years....transistor/IC and other semi-conductors never go bad.
I suggest you will need to go for electronic service of the system......do not fiddle with the pivot screws....this will lead to more problems.
All the best!
 
Thank you amit46. This sounds like something that is definitely out of my league in terms of being able to accomplish. Howerver, after thinking about it some more, I have the following observations that might provide more insight as to what has happened.

After not using the table for several months, I began using it again a couple days ago and, thinking it would be a good idea to clean the stylus removed the headshell from the arm as it is easier to do a thorough cleaning off the arm on my bench. Removing the headshell necessitates grabbing the arm and unscrewing the headshell, during which operation one will inevitably move the arm a bit from side to side, up and down in the carriage.

Upon finishing the cleaning, re-installed the headshell and that was when the problem first surfaced. When I push the 30 button, the arm acts as normal and lifts, moves to the proper set-down point over the record, and then the arm drops to the record. During this phase as the arm is dropping, I noticed that there was a drifting from the intended setdown point and into the first part of the track. Pressed CUT and the arm returns to the original rest position. Pressed 30 again and the same thing happened. Pressed CUT again and tried the operation several more times with same results......arm keeps drifting to the left.....

Last night, I had an idea that maybe the mechanism just needed to be "re-set" and so I used the << and >> buttons to bring the arm about half way through the record. Pressed DOWN button and it dropped straight down, no drifting. Pressed CUT and then 30, the arm came to the beginning of the record and straight down, no drift. I tried the CUT and 30 buttons about 10 more times with the same result, arm came straight down.

After pfcs49 suggested grabbing the arm and moving it slightly left and right to see if the carriage would follow as intended, and it did, pressed CUT and the arm returned to the rest position. Pressed 30 again and the problem behavior was there again, arm drifting towards spindle as it came down. I then used the << and >> buttons again to move the arm to the center of the record, pressed DOWN and it came straight down. Pressed CUT and it returned to rest position. Then pressed 30 and it came over to the beginning of the record (lead in groove) and dropped straight down.

So, I'm thinking that any physical manipulation of the arm, which I don't normally do unless cleaning/changing cartridges, will cause the mechanism to not function as it should. The other funny thing is that I've changed carts on this arm a fair number of times in the past but have not noticed that it caused this unwanted behavior, so something is definitely going on and seems related to manipulating the arm with one's hand rather than using the buttons. I'm very careful though, and try not to move it too far in any direction while handling it to get the headshell off. When you go too far, you can definitely feel that there is slight resistance but I have not done that very much at all.

Hope this information can lead to more accurately diagnosing the problem. I sure hope I don't have to have all the electronics on the boards replaced.....right now I can get it to function properly by doing the exercise described above.

Let me try to turn it on now and put a record on to see what happens after sitting over night......stay tuned.....

15 cycles of pressing the 30 button and after it comes down the CUT button, arm drops straight down as it should. I'm willing to bet that if I take the headshell off and re-install it, the problem will then again be there until I do the << and >> trick which seems to "re-set" the arm in some way.

I really like this table and want to make sure that there isn't something that has gone awry. If anyone has any other observations/comments/suggestions, I would really appreciate hearing from you.
 
If the tonearm carriage is stationary when the arm drifts, it's not a servo issue.
I don't know this but hunch (EDIT: WRONG! see my next post) that the centering function should keep the arm centered/constrained until the stylus takes up the weight and the centering lineage continues to fall. (I assume the up/down mechanism includes the centering V in it's function. Lift/drop is controlled by a return spring (up) and a solenoid which retracts allowing the lineage to sink down, slowed by the damper piston inside the bearing housing. This why if you unplug the unit, the arm goes up.)
Since yours may have a problem in this, I'll try getting downstairs and feel up my arm as it's cueing down to see if it's free or constrained.
 
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The carriage moves to the left but only after the arm starts to drift first, which is what the carriage is supposed to do if I'm understanding you correctly? Thanks, will await your findings.....
 
Fishead said:
The carriage moves to the left but only after the arm starts to drift first, which is what the carriage is supposed to do if I'm understanding you correctly? Thanks, will await your findings.....
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Yes.

So I played with mine. The arm is unconstrained once it starts to drop and is fully free to be moved on its pivots; I expect if I could blow sideways on the head shell, it would move to its arc-limit. When raising, the centering device only acts in the last bit of up-motion.
I dropped it near the edge of the platter and grabbed it and exercised the servo, moving it laterally and seeing the carriage mimic my moves.
When I kept it pushed to the right, I see that when it hits the right side limit switch, the platter motor (and the platter) stops, which is handy because as long as I don't hit the power button, the arm is in the released state but the servo is not active! Maybe in that torpid state, you can REALLY study what goes on with the arm that's causing it to swing to the left?

Question: does it only do this when cueing on a 12" record? Can you cue 7" w/o problem?
If it does it cueing 12", does it not if you then use the (<<L/R>>) <<L button to move it from park to over the lead-in groove, and then the down button?
Interesting that moving it out over the record seems to cure it.
More and more seems like something dumb is the cause!
Something under the tonearm base, some piece of household detritus? a little piece of paper? Part of a tissue paper someone was using to wipe it down? Mouse turds? A fly? A spent condom irresponsibly thrown after too much wine and fun?
 
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I have not tried it with a 7" record.
When I tried cueing it with the << button, it also did the drift thing until I did the <<L/R>> maneuver in the middle of the record and then hit DOWN. That seems to be what puts it back in the proper mode of operation when hitting 30 from the rest position which I have done dozens of times this morning and it works without fail. If I were to do the maneuver you described yesterday, from rest to the edge of the record and then DOWN and grab the tonearm and go side to side with it, it then does the drift upon hitting CUT and then 30, in which case the arm moves from rest to the cueing position and slowly starts to drop and drift. Then, if I go back to the center of the record with the << button, go back and forth with << and >> a few times maybe half an inch both ways, hit DOWN it comes straight down, hit CUT and then 30 and it cues just fine. Go figure....I have checked thoroughly for any detritus, including condoms, and none is/are present. At least I have a way to cure it, eh? I think I'll take it apart in the near future and look at the innards.....perhaps there is something in/on the transport that I can not see from the outside? Really appreciate your time and effort pfcs49!
 
Dumb question, but did you make sure it's level? There's lots you can't see from the outside, there's three belts, an idler wheel, and that huge flat belt with its tension springs. I'm fixing up a PX-2 right now, and it's quite a contraption.
 
"I have not tried it with a 7" record."

With an LP on it, try the 7" button; it should go where a 45 would be and drop there (onto the LP). Mildly curious. Can't see any distinction between the two sizes except how far it travels before release.
I'd be playing with it, attempting to see if there's a logic to the problem. Like, if I deflect the parked arm to the right then hit 30 (play 30 for non PX folk), how does it behave.
Then deflect left and check.
I also wonder if the tiny tonearm (signal) wires are somehow involved, getting moved/streched by some thing askew under the arm and that your lateral dance is like combing your hair to one side or the other?
Weird!
 
The new poster remind me about reading comprehension issues:) (he checked level)
We have concluded that the cause is that the arm itself is predisposed to drift towards the inside of a record, correct? Which then causes the carriage to move (which is expected)
 
pfcs49 said:
The new poster remind me about reading comprehension issues:) (he checked level)
We have concluded that the cause is that the arm itself is predisposed to drift towards the inside of a record, correct? Which then causes the carriage to move (which is expected)
Click to expand...

Yes, admittedly I didn't read all the way though, my bad. The one I am repairing has issues too, I changed the belts, cleaned the large belt and flipped it around, and used rubber renew on the idler, but still it slips a tiny bit when you cue it using the arrows. Sure would be nice if someone made a new flat belt for this thing.
 
Yep, I did make sure it was level as previously stated but there is always the chance, which is why I checked it again. I will keep playing with it and see if I can discover the logic, that's a good point. There is usually an explanation. I did the 7" thing and when it drifts at 30, it also drifts at the 17 (mm) button. Once I have done the correction maneuver, let's call it, then it drops straight both at 30 and 17......

I'm going to have to head to the office and will check back later. Thank you all again, it feels like I have a whole team of techs helping me. Guess that is what AK is all about and I truly appreciate it.
 
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