PL-400 Speed Variation

[Texaco]

Hey all,

Long time viewer and admirer of the "Pics of your listening space" thread, somewhat newly registered, and here with my first post. I've got a 1979 Pioneer PL-400 turntable that was a gift from my aunt who got it as a wedding gift 40 years ago. I've used it for the past few years with a Nikko NR-719, but recently decided to upgrade my system with a Yamaha A-S501 amp and matching silver-faced '74 Yammie CT-800. Aesthetically and sonically it's been a killer overhaul.

Over the past few weeks I've had issues with the Pioneer, though, with it doing quick speed variations throughout a record. I've actually sent two copies of Chris Stapleton back thinking the albums were warped (that specific pressing is known to have issues) and his solo voice and acoustic guitar were unbearable with the pitch changes. Today I've put on a few records I listen to regularly and heard the same pitch variation, enough so that I sat there and watched the platter strobe with my iPhone in hand to time the variations.

At the outside of the platter the variations occur every 7.8 seconds, at the inside of the platter they occur every 6.45 seconds. (both are averages, +/- lag time for my eyes and thumb to time it)

This turntable doesn't have speed adjustment of any kind, and is direct drive. I'm handy with a soldering iron (I'm a touring audio engineer by trade) but am relatively new to the "modding hi-fi gear" realm. Any input from the intelligent masses here on what I might be able to do to fix this issue? It's officially bad enough that I've turned the table off until it's fixed... can't stand hearing it distort good music!

Thanks in advance!

Ryan

 

[Greenie]

Greetings and welcome.

I should say my expertise and skills are unlikely to match your own.
However I've had several DD turntable from the 70/80s which show similar symptoms to your Pioneer.
The service manual is available from https://www.vinylengine.com/library/pioneer/pl-400.shtml
It seems there are internal speed adjustment pots for 33 and 45 rpm which may resolve your issue. In most quartz lock DDs I find once they falter they tend to stay a bit unpredictable sadly.
One nuclear option which did sort an old Denon DP23F was when all else failed to blitz the internal speed pots with switch cleaner, working them vigorously while doing so.
This is a last resort however and may even make things worse.
These turntables will no longer have new control boards available but you might get a complete TT spares/repair on ebay, of course that may have a similar problem to yours so don't spend too much

On final thought. I did have a DD turntable which was very sensitive to domestic voltage variations. I noticed my wobble tended to occur around 4-6pm when use was at it's peak.
That was on a non Quartz lock motor though.

Good luck whatever.

 

[Texaco]

Greenie,

Thanks so much for the information. I was able to read through the manual you linked to, cross reference the info in there to a few other Google searches, and find a whole bunch of information that I hadn't found previously about this speed variance being a known issue with this turntable. By lifting the platter off and spraying the speed selector switch with Detoxit cleaner, as well as vigorously tweaking the speed adjustment dials underneath the unit while applying Detoxit, I was able to get the table to play back at a locked speed as it should! Re-balanced the tone arm after this little bit of surgery, and now all is well.

Again, appreciate your response and suggestions!