Pitch Issues on my Direct Drive TT

[rohitnaargolkar]

Hi All,
I have a Pioneer PL-640 Direct Drive TT and since the past week I have been having pitch wavering problems which become less pronounced towards the end of the record. Would welcome suggestions to deal with this issue, thanks.

 

[aks07]

Have you checked the primary suspects?

1. Dry bearing.
2. Clogged/intermittent pots.
3. Faulty electrolyte capacitors.

Get the service manual before doing this.

 

[rohitnaargolkar]

Hi aks07,

Thanks for the tip will do that asap meanwhile I played a 45 rpm record and it play beautifully, would that point towards some specific problem.

 

[aks07]

Perhaps yes.

Is it an automatic or semi automatic model? Can check underside to see for any mechanical problems in the drive mechanism? These could be incredibly complex.

But I would first address the usual causes as listed in previous reply. If they are ok and the fault is only at 33rpm range then the issue could be slightly more complicated. There are multiple parts such as Sensors, semiconductors passives etc that could have gone bad.

If you have experience with electronics then kindly consider downloading the service manual and understand it. Look for troubleshooting pages. I am sure this scenario must be mentioned.

 

[rohitnaargolkar]

Thanks so much, will do the needful with the help of a friend who is a electronics engineer, much appreciated.

 

[TD150]

Rohit, if you are comfortable opening the unit you will find two variable pots VR ( one for 33 & other for 45 rpm). Do check the VR for 33 (it would be marked 33rpm or similar). Try to deoxit/ free it from oxidation and this might work. In most of the cases the problem lies with oxidation in this component which results in irregular speed of motor.

Since you mentioned the 45rpm works flawless, it is a sure case of deoxidation required for the VR of 33rpm speed pot.

Hope this helps.

 

[prepress]

^+1, you just need to it carefully. Keep in mind the actual position both presets, you may touch 45rpm variable preset. Seems your TT doesn't have stroboscope to check the correct speed so look if you can do this while playing record.

 

[Record Player]

WD 40 is your agent to use when cleaning the Pots. I had a similar issue on an Akai TT and cleaning the Pots with WD 40 did the trick. Also, WD 40 is a great agent to use when cleaning pots, interconnects etc.

 

[aks07]

....Seems your TT doesn't have stroboscope to check the correct speed so look if you can do this while playing record.

Can you really do this? Golden ears ! I think its is very difficult, though not impossible, to set the perfect pitch this way. Why not simply use a strobe disk?

I cant seem to get it spot on even with visual aid. But it helps that with my slowing faculties, I hardly note any minor pitch variation. Life is simpler if you stop being a perfectionist.

Back to the TT, I once fixed an AKAI with a similar fault. The pots, spindle etc was cleaned. The electronics tested fine. But still the problem persisted. Then in exasperation I asked an old mechanic. He suggested me to lift the TT on a jig and inspect it from below when in operation. And the problem was spotted. Usually the arm has an small extension tab that works the micro limit switch. This is very precisely aligned but somehow this arrangement had got disturbed. The tab was intermittently working the limit switch in a rapid on/off sequence. The power to the motor was not steady resulting in speed variation. Therefore, I had earlier suggested to look into drive mechanism also along with the pots and the spindle.

If the cleaning/adjustment doesn't help then check the elcos and then so on. Does it use a Quartz referenced controller?

 

[rohitnaargolkar]

Thank you all for the suggestions since I have no nothing of electronics will do the above with some help, thanks so much, will post the result asap.

 

[greenhorn]

WD 40 is your agent to use when cleaning the Pots. I had a similar issue on an Akai TT and cleaning the Pots with WD 40 did the trick. Also, WD 40 is a great agent to use when cleaning pots, interconnects etc.

I would not suggest WD 40. It does not dry, and stays on the components gathering dust. there are contact cleaner sprays available online - they are more expensive, but get the job done much better.

If you're on a budget, then why not use simple Isopropyl alcohol ?

 

[rohitnaargolkar]

I saw something called CRC like an anti oxidant spray will check availability, thanks

 

[ZoltanToth]

Hi All,
I have a Pioneer PL-640 Direct Drive TT and since the past week I have been having pitch wavering problems which become less pronounced towards the end of the record. Would welcome suggestions to deal with this issue, thanks.

Hi,
It's been a long time you posted this but now in 2024 I have exactly the same issue. The TT is the same type (PL-640) and all the symptoms including the 33 rpm speed issues and 45 rpm speed non-issues are exactly the same.
So my answer is that could you at that time somehow manage the issues, solve the problem and how?