Yamaha px-2

[Ageenbeing]

Strange behavior....all controls appear to be working properly . Either automatic or manuel cueing an album will play for 24 seconds, then will slow down to a stop as the arm raises, it stays like this for !2 second, then resumes playing with this 24 seconds on then 12 seconds off stop, until the album finishes.
Any clue what's happening or what to test

 

[Dr. Ear]

Clean the photo interrupters with compressed air. Next check the alignment of the solenoid contacts at the back of the TA. You have to remove the service panel in the rear.

 

[Dr. Ear]

It‘s a tiny magnet activating the solenoid, not a contact.

 

[Ageenbeing]

Thanks for responding. Great to know that you are out there and know the PX2. I will clean the led photo interrupters later today. Can you explain the location and adjustment for aligning the solenoid.
Some further information:

1. This stopping starting behavior will occur if the tone arm is not in contact with album.
2. The original problem was the TA would not track. It proved to be insufficient power the the motor.
3. This was corrected by replacing TR4.

Now everything seems to be working except this start stop behavior. The voltages to the LED photo interrupters are a little low to specs. Do you think this can be the issue?

 

[Dr. Ear]

At the (viewed from the front) rear right corner of the tonearm there is a tiny glass tube (the solenoid). A T-shaped metal arm holding a small magnet, fixed with one screw should come close to the center of the solenoid when the tonearm is raised. Check the position of the magnet if it is off center (or if it is still there, it is fixed with glue).
If the voltage to the LED‘s of the photo interrupters is low, you can try replacing R37 (560 Ohms) by a slightly lower value (480-520 Ohms). If the LED‘s are tired then you have to replace the photo interrupters. The photo interrupters are good for any kind of weird malfunction.
Did you replace the motor belt and clean and tighten the arm drive belt?

 

[Ageenbeing]

Hi DrEar, Simple did not work. Compressed air on photo . I do not see the glass tube you are discribing. Do need to remove the am control assembly or can it be seen and adjusted with it in place. I will try to change the resistors next. Since In the past I had tightened the springs on the drive belt and replaced the small rubber belts.
Anyway to test the photo receptors prior to replacing them.
I appreciate your knowing and sharing.

 

[Dr. Ear]

Try to increase the voltage to the diodes by lowering the value of R37 a bit. Another issue I once had causing a weird malfunction was broken solder joints at the connectors of the cables from the main pcb to the tonarm assembly.

 

[pfcs49]

Hi DrEar, Simple did not work. Compressed air on photo . I do not see the glass tube you are discribing. Do need to remove the am control assembly or can it be seen and adjusted with it in place. I will try to change the resistors next. Since In the past I had tightened the springs on the drive belt and replaced the small rubber belts.
Anyway to test the photo receptors prior to replacing them.
I appreciate your knowing and sharing.

I think DrEar is describing the earlier PX2 tonearm which had a worm drive as the first stage of arm-motor speed reduction and only two stages of belts while the more common later type has 3 stages of belt drives.
The later arm also has a completely different arm height position switch scheme with leaf spring-contacts and an adjusting screw in a different location.
The later PX2 arm is identical to all the PX3 arms.

 

[Ageenbeing]

The challenge continues... DrEar, I began to replace the R37 however I noticed it is rated at 47K not the 560 ohms you indicated. Would you please verify the resistor number that would change the voltage to photo interrupters.
It appears that I do have the later arm which pfcs49 suggested. Should this be suspect for the intermittent stopping and restarting and if so any guidelines on how to adjust. Hope I am getting closer to spinning vinyl again.

 

[Ageenbeing]

I think DrEar is describing the earlier PX2 tonearm which had a worm drive as the first stage of arm-motor speed reduction and only two stages of belts while the more common later type has 3 stages of belt drives.
The later arm also has a completely different arm height position switch scheme with leaf spring-contacts and an adjusting screw in a different location.
The later PX2 arm is identical to all the PX3 arms.

The challenge continues... DrEar, I began to replace the R37 however I noticed it is rated at 47K not the 560 ohms you indicated. Would you please verify the resistor number that would change the voltage to photo interrupters.
It appears that I do have the later arm which pfcs49 suggested. Should this be suspect for the intermittent stopping and restarting and if so any guidelines on how to adjust. Hope I am getting closer to spinning vinyl again.

 

[Ageenbeing]

Try to increase the voltage to the diodes by lowering the value of R37 a bit. Another issue I once had causing a weird malfunction was broken solder joints at the connectors of the cables from the main pcb to the tonarm assembly.

The challenge continues... DrEar, I began to replace the R37 however I noticed it is rated at 47K not the 560 ohms you indicated. Would you please verify the resistor number that would change the voltage to photo interrupters.
It appears that I do have the later arm which pfcs49 suggested. Should this be suspect for the intermittent stopping and restarting and if so any guidelines on how to adjust. Hope I am getting closer to spinning vinyl again.

 

[pfcs49]

I took a quick look at my PX3 and PX 2 manuals.
In both diagrams, pin #6 to the sensor board is 12v/B+ power.
Pin 7 is return to ground through a 680 ohm resistor; in px3, R28, in px3, R37
On the px2 diagram I have penciled in 6v as the value at pin 7 before the resistor, so 2v to each sensor LED and 6v across the resistor.

 

[Dr. Ear]

Sorry, Phil is right. In the PX-2 it is R28 / 680 Ohms. I accidentally had the PX-3 schematics stored in the PX-2 folder, where it is R37.