Yamaha PX-3 Tone Arm Issue

[BillWojo]

Well whatever is failing isn't going to get better on it's own. Sounds like an electrical problem. I would recap the boards before something gets permanently damaged. My guess is that a cap is shorting out and heating up diverting power to the drive motor. It cools down and works fine until the cycle starts again.

BillWojo

 

[RCHeliz]

Well whatever is failing isn't going to get better on it's own. Sounds like an electrical problem. I would recap the boards before something gets permanently damaged. My guess is that a cap is shorting out and heating up diverting power to the drive motor. It cools down and works fine until the cycle starts again.

BillWojo

Precisely what my next step is, will not mess with it until that step is competed. Components are on order based on the list/info above! (added the standard diodes from the list too, just in case) Thank you !

 

[Dr. Ear]

Regarding springs losing tension: only to the extent they are (very) rusty. Any tempered spring (which these surely are as you see who rebounding the tail!) will not loose rate in a low stress and very slight activity application like this.

Sorry, springs are definitely losing tension over time Ask Yamaha PF-800/1000 owners. They have a problem with stretched suspension springs. It may reach a point where proper adjustment of the subchassis is not possible any more. Next, take a closer look at the feet of any PX-2. The springs are compressed by just bearing the weight of the heavy turntable for more than 30 years.

 

[Dr. Ear]

Anyway, I agree, seems like an electrical issue. Is there a voltage drop when symptoms appear? Maybe I missed something, but did you check the voltage regulators at the main board?

 

[Nashou66]

Anyway, I agree, seems like an electrical issue. Is there a voltage drop when symptoms appear? Maybe I missed something, but did you check the voltage regulators at the main board?

Right and you can check the voltage going to the motor right at its connector.

If the voltage does not change then you have may have a motor issue.Then id check to see if current draw changes there.
You should check voltages at turn on then later when the issue pops up.

Hopefully its not the arm motor craping out.

Athanasios

 

[pfcs49]

https://www.europeansprings.com/springs/technical-information-springs/spring-durability/

 

[RCHeliz]

Well what do you know, I have isolated the issue to the LED that shines on the dual CdS sensor in the arm. The problem is the LED does not light up fully. After the recap it has gotten worse where the LED is very dim and slightly flickers.(before the issue was more intermittent with LED losing brightness after 30 min, now it stays in this dim state from cold power up) So recapping brought the voltages within spec and caused the already bad components to crap out perhaps.
Everything else works as before except arm does not respond to L/R tilt.

LED itself appears ok but the circuit that drives it seems to be the problem. Here is a video showing the LED in the arm not lighting up fully in order to properly track on the record:

Update:
I think I found the problem. TR4 is blown!

 

[pfcs49]

Good work!!
Looks like you handled it yourself. Isn't that satisfying?
Me? Well another AKer lit a fire under my butt. I spent most of the day finishing up the two (other) PX-2s that have been languishing in my basement about five years. They're both pretty well good to go excepting polishing the covers which I hate! Polishing something from a wheelchair gets you very involved with the process (as in wet and dirty!)

 

[RCHeliz]

Good work!!
Looks like you handled it yourself. Isn't that satisfying?
Me? Well another AKer lit a fire under my butt. I spent most of the day finishing up the two (other) PX-2s that have been languishing in my basement about five years. They're both pretty well good to go excepting polishing the covers which I hate! Polishing something from a wheelchair gets you very involved with the process (as in wet and dirty!)

Yes sir very! I did get help with troubleshooting via email from Ty..(A fantastic engineer)
A simple led problem that killed the whole operation...

I hear you, my cover is brand new...

 

[RCHeliz]

Here is led working:

 

[RCHeliz]

And here it is, smooth and nimble with perfect 90 degrees action. Both L/R read even at full deflection -3.6v and +3.6v yeyii!

 

[RCHeliz]

Final tone arm mechanical and optical calibration.

Center low arm 0.0v
Full LEFT = -3.7v
Full RIGHT = +3.7v

Im a bit ocd so I calibrated it perfectly to even voltages both sides full deflection and 0v in the middle. Had to adjust the CdS shutter centering screw below the arm and finally VR4.

Voilla!

 

[audiocrzy]

Good work!

 

[pfcs49]

Good plan, running the system "out of the box".
Kind of how I work on B&O 8000/8002s, with the board and the keyboards removed and laid on the TT base with cardboard under to insulate.
Not so viable on PX-2s which have two transformers and two circuitboards; much more electronics than PX3.

 

[BillWojo]

Nice write up. I have never had to get that deep into my tonearm and those are the first pictures I've seen of the inner workings.
I take it that the black plastic pie shaped piece on the tone arm pivot is the shutter, there is a small hole in it. The two dots below the hole, are they the receptors that pick up the laser light? Going full left I see only one exposed and going full right it looks like both are exposed. Am I correct?
To the left it looks like a shiny rectangular block, is that the solenoid that picks up the arm?
I like the way you pulled out the boards and operated the tonearm functions on your work bench. Makes it easy to make adjustments.

BillWojo

 

[RCHeliz]

Thank you! That shutter is made of metal actually and it is adjustable(centering) via the screw above the small spring.
When the LED shines on the dual CdS below the arm moves and it is proportional, more tilt more speed.
The dual CdS photo sensor is custom and unobtainable. Part # is P1234 in the svc manual LoL...

Yes and Yes!

 

[RCHeliz]

After full cleanup, calibration and recap(recapped main platter motor also), ready for re-assembly.. Unit was pretty much new so I soap/water washed the chassis for oils etc and NuFinished the buttons to remove petina sides and top, bathed buttons springs in light tonearm oil etc.

 

[RCHeliz]

Some shots before the cleanup:

 

[RCHeliz]

Can someone with a Yamaha PX-3 do me a huge favor? Play a record on your table and take two photos from the top when the needle is at half the record play area similar to my photos below. I would like to look at the tangency of the arm to see if I should adjust the 90degree angle to be more tight. See the example pictures below. Let it play a bit before taking the pics.
It would be a great help. Thank you in advance!

 

[pfcs49]

Does anal compulsive have a hyphen

This has always been an issue for me because I can't stand to look so I take pictures.
Yours looks rotated, in. I base this on the relation of the arm parts to the stationary tonearm carriage parts. (you cannot judge from the rear/counterweight, it is floppy)