Dir Drv TT spinning at about 100 rpm

[67dylan]

The OP's complaint was rogue speed (100 rpm?).
That happened to me once with one of the cheapo Pio's (PL-300) someone left for me to "see what I can do" and never bothered to phone about it since. The feather weight platter was going so fast I was worried it'll go air borne and chop my neck. It only had 9 lytics on it, all cheap Nippon Chemi's and Rubycons from the 70's. I tested only the PS cap for ESR and it was way off any of my older charts. I didn't bother with testing the rest, most were low voltage low capacitance EC's so it was a five bucks worth of a complete recap. But that wasn't the end of it. I gave that abandoned TT to a forum member who was sold on the quartz lock drive and expressed interest in fixing it, as it was. He just replaced the two trimmers that probably developed dead spots, and that, plus the earlier recap, did the trick.

The PL4 and PL300 are different beasts. IMO very different. Parts, IC's, and operations aren't even close. Comparing the repair of one doesn't mean that fix will repair the other.

A dead spot on a pot will still allow more/less speed than an estimated 100rpm depending on the rotation of the pot. The dead spot would have no rpm. That is not in his description of problems he's encountered. He can always check the output of the pots if he has the know how and a MM. Now consider the IC's. There is a reference v on one and Hall element on the other. A bad cap on either of those will do what?

Now granted I'm taking a guess based on no real technical data from the original t-shooting. We're all giving info and he should start out with the simple stuff...like deoxing ALL switches/pots & checking voltage input/output. Then go from there. Otherwise, we're all blindly shooting darts

 

[restorer-john]

You need to look at the ring magnet on the motor bell cover. It should be not cracked or have any pieces missing. Sometimes, they fall off altogether and prevent the PCB track loop getting a valid FG rotation value via the PCB coil pattern/sensor.

Also, follow the flow chart here:



The Hall sensor array in those units can also be a cause of speed over-run. Also check C8.

 

[CavScout]

Update: replaced ALL the caps.
Same problem.
Also , same problem is sometimes it runs backwards

 

[67dylan]

Even tho I guessed it was the caps, guessed wrong I might add, did you check the voltage output? restorer-John posted a great flow chart that describes what the outputs should be for IC PA2007. I would have started there and trace where the faulty part or parts may be on that board. I'm sure there's another flow chart for the other board or IC as well. Did you DeOx all pots? Verify the pots are working properly too. Do you know how to use & do you have a MM?

 

[CavScout]

I cleaned the pots.
I know how to use a multimeter when instructed but can I scope from start to finish ? Nope.
How do I check the voltage output?
What setting on the MM? Where do I put the black and red leads ?

 

[67dylan]

You want to set the MM to DCV, DC voltage. Make sure the leads plugged into the MM are in the correct inputs: V?Ohm for red & ground for black (some MM have an input for just current). If it has auto ranging use that, otherwise set it to 20 (meaning checking less than 20V). The black lead goes to ground while the red lead goes to which point you are checking. Now, you will need the TT powered to test it. I can't stress enough to BE CAREFUL. You don't want to accidentally zap yourself. The flow chart will tell you where to check on the boards. I'd write down the voltage at each check. If I wasn't clear, you have to run the TT to check the voltage. Make sure you protect your cart or remove it or the stylus; accidents happen. You're probably going to have to lift the arm and put it on the platter or old crappy record while the platter rotates. Check the voltage and see if it's in range. If not that's one of the faulty parts. Check both IC's. Check the pots...to do that you want to check continuity and that it ranges from low to high with no dead spots so rotate slowly. I hope it's clear enough for you. Any questions please ask.

 

[CavScout]

Thanks

What is an IC ?

When you say GROUND do you mean a metal part of the TT or a ground wire ?

 

[67dylan]

IC is Integrated Chip. PA2007 is on one of your boards.

Ground as in the black wire, NOT a metal part of the TT.

 

[CavScout]

Sounds like I need to learn how to read the schematic

 

[EngineerNate]

You need to look at the ring magnet on the motor bell cover. It should be not cracked or have any pieces missing. Sometimes, they fall off altogether and prevent the PCB track loop getting a valid FG rotation value via the PCB coil pattern/sensor.

Also, follow the flow chart here:

View attachment 1170301

The Hall sensor array in those units can also be a cause of speed over-run. Also check C8.

The first Pioneer table I fixed had this problem. Made an audible scraping noise but managed to rotate at ~30RPM, though with little torque. The magnet had come unglued and simply split in one single location so I glued it back together and to the bell housing as cleanly as possible and reassembled after using some nail polish to seal the PCB back up where the rubbing had worn through the lacquer. Worked a charm! I'm sure there was some disruption to the 200 individual magnetic poles on the FG magnet, but it was not enough to cause audible disturbances during rotation.

@67dylan - While the PL-4 doesn't use the quartz circuitry of the PL-300, I've been inside a PL-250 and a PL-7 and I'd hazard a guess the quartz versions of the PL-x line have more in common than not with the PL-300 internally. The motors are nearly identical in operation.