Yamaha P-(X)50 Turntable DIY Maintenance Thread P-350, P-450, P-550, P-750, P-751, P-10, P-20
Used 8 cassette tape cases for the 4 corners of the bottom plate to elevate it. Put weight on the bottom plate.
use heat and weight.
(Plastic. It's so damn plastic-y)
like i said, it was a lot of pondering, staring, waiting for the mind to clear and have that AHA...
SmileyFaceEQ
Super Member
I don't know if there are many other 850's still floating around.
Well. Gave it another run. It has sat on a firm surface for 24 hours and I can see some of the bowing of the bottom plate is back. But it survived a slight discwasher brush level of down pressure without scraping. And played 1 side very well. Not a full cure.
Now the next bad news. I get another disc cleaned. Tiny hint is scrape. Remove mat and give platter a tiny up pull. No movement. Replace mat. No scraping. I hit play, the arm returns to the stand then reverses and gets placed and lowers. And it doesn’t sound as good.
Further inspection, the bearings/action is off. This arm might be the Achilles. I think the base can ultimately get better straightened and the scraping problem put to rest, am optimistic about that.
Going back to arm screw tension tweaking next.
Do I want to go deeper and source another arm?
I suspect this one won’t withstand the repeat use.
Now the next bad news. I get another disc cleaned. Tiny hint is scrape. Remove mat and give platter a tiny up pull. No movement. Replace mat. No scraping. I hit play, the arm returns to the stand then reverses and gets placed and lowers. And it doesn’t sound as good.
Further inspection, the bearings/action is off. This arm might be the Achilles. I think the base can ultimately get better straightened and the scraping problem put to rest, am optimistic about that.
Going back to arm screw tension tweaking next.
Do I want to go deeper and source another arm?
I suspect this one won’t withstand the repeat use.
The base of the 850 and 750 are not generic plastic, they're a composite and I wouldn't expect it to keep a bend... but maybe?
Have you tried shimming the spindle where the platter sits? That would raise the platter without affecting the rest of the mechanism alignment.
Have you tried shimming the spindle where the platter sits? That would raise the platter without affecting the rest of the mechanism alignment.
SmileyFaceEQ
Super Member
Shame that it is curved.
i ended up finding a p 350 unit to use as a donor. Distance was far but price was right.
the base is flat! going into the weekend, my plan was to leave the bottom cover plate from the 850 in a car with the windows up and let the sunshine heat everything up, while weighting it for a reverse bend. it never got above 60*. when the opportunity to get the 350 came up, i went that route instead.
the new bottom plate from the 350 might/should be enough straight to reconcile the 850 base's deviation.
the tonearm action is good. but there's a significant hum. at this point, the intended goal is to use the tonearm from the 350.
the base is flat! going into the weekend, my plan was to leave the bottom cover plate from the 850 in a car with the windows up and let the sunshine heat everything up, while weighting it for a reverse bend. it never got above 60*. when the opportunity to get the 350 came up, i went that route instead.
the new bottom plate from the 350 might/should be enough straight to reconcile the 850 base's deviation.
the tonearm action is good. but there's a significant hum. at this point, the intended goal is to use the tonearm from the 350.
early on, this (shimming) was the 1st direction i took.
my efforts were somewhat half-assed with metal washers and/or trimmed rubber grommets. what i concluded was that *any* amount of platter not being in position on the spindle yielded inconsistent spin rate and just the slightest bit of eccentric tilt.
it was later that, while staring at the unit while elevated on paper towels, i found that just the *slightest* bit of upward push under the spindle took away the scraping... and how i locked onto the "curved base" theory.
I stared at pics of the 850 vs 350 arms and their assemblies all week long. I had a hunch they weren’t exactly inter swappable.
This is the 850 underside. Do I want to disrupt this when it’s all functioning well? I’m talking myself into a bearing swap instead of full arm base. Plus, the 350 has a hum somewhere and I never figured out if it was a problem in that arm.
This is the 850 underside. Do I want to disrupt this when it’s all functioning well? I’m talking myself into a bearing swap instead of full arm base. Plus, the 350 has a hum somewhere and I never figured out if it was a problem in that arm.
Clean those before you think to remove, they look salvageable!
Do you find that the base is the same material and weight between the 350 and 850? I thought the 850 was heavier, plus the buttons and I don't know if the cutouts and mounts are the same.
Only the 750 has adjustable vtf, I've totally forgotten to ask if your arm is level while playing on the 850.
SmileyFaceEQ
Super Member
Get some 99% alcohol and get to cleaning. I would try a a small paint brush to avoid leaving cotton swab particles behind to contaminate the bearings to start out and test for progress.
Not sure how to get either bearing set out. That housing seems to be pressure fitted, not held be screws.
If I got the tube out, then what? It seems the only opening is at 90 degrees from the bottom.
Break the rubber or plastic outer rim of the bearing and pry out from the edge?
Don’t want to pry from the center opening.
Is the first step to remove the tube?
If I got the tube out, then what? It seems the only opening is at 90 degrees from the bottom.
Break the rubber or plastic outer rim of the bearing and pry out from the edge?
Don’t want to pry from the center opening.
Is the first step to remove the tube?
I think you'd need a puller of sorts, to reach inside and then use to pull straight out. I don't think they were meant to be removed.
This is why swapping the entire arm seems to be the ideal solution.
This is why swapping the entire arm seems to be the ideal solution.
This is the conclusion I arrived at after returning to the project late last night.