Pioneer PL-550 counterweight ?

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woodmakesitgood
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Pioneer PL-550 counterweight ?

Post by woodmakesitgood » 19 Aug 2017 23:56

I'm setting up this table, and the tonearm won't balance unless the counterweight is moved all the way forward. It can work like this, but it seems strange, and limits the choice of headshells.
I had to put my heavyish Jelco 750 shell on there.

There is no subweight installed in the back of the counterweight, which was my first guess.
What else might cause this?
The back of the arm is bent down a bit, which is a little unfortunate.... :?
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woodmakesitgood
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Re: Pioneer PL-550 counterweight ?

Post by woodmakesitgood » 20 Aug 2017 01:20

hmmm, the weight is 105g which I think is 4g heavier than a stock weight would be.

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Re: Pioneer PL-550 counterweight ?

Post by Copperhead » 20 Aug 2017 02:16

woodmakesitgood wrote: The back of the arm is bent down a bit, which is a little unfortunate.... :?
Look down the counterweight stub, there's a screw you can tighten up to make the rod erect and stiff again. Bit of age related sagging.

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Re: Pioneer PL-550 counterweight ?

Post by woodmakesitgood » 20 Aug 2017 03:45

Copperhead wrote:
woodmakesitgood wrote: The back of the arm is bent down a bit, which is a little unfortunate.... :?
Look down the counterweight stub, there's a screw you can tighten up to make the rod erect and stiff again. Bit of age related sagging.
"age related sagging" is becoming a reality... :)

There doesn't seem to be a screw to tighten up the poor flaccid rod though.
However, the extra weight needed at the headshell is the result of the extra weight on the rod.
The final bit that extends off the back is a little weight that can be screwed off. Without it, the Jelco shell is too heavy, so I'll leave it on for now.

Maybe some superglue will straighten up that joint quite nicely.

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Re: Pioneer PL-550 counterweight ?

Post by Copperhead » 20 Aug 2017 16:40

woodmakesitgood wrote:There doesn't seem to be a screw to tighten up the poor flaccid rod though.
No one should put up with that amount of flaccidity, if you handle it properly it will stiffen back up.

Have another look down the backstub, it is attached to the tonearm with a bolt. Someone here pointed out a Technics tonearm which must be dismantled in order to tighten up the stub. Doubt your Pioneer uses that design.

All the tonearms with removable back stub I have ever owned use the bolt to fix it in place, and a compliant material do add some de-coupling. Don't use superglue, I am sure you can tighten it up.

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Re: Pioneer PL-550 counterweight ?

Post by ttomt » 20 Aug 2017 20:37

I have just fixed a sagging tonearm weight. There should be a plug/cap/piece of arm or something that unscrews/pulls out/unclips. Check bolt not bent, replace if necessary, be careful if you try to straighten it because it screws into soft alloy and could ruin thread.
Good luck.
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Re: Pioneer PL-550 counterweight ?

Post by woodmakesitgood » 20 Aug 2017 22:58

The end stub does screw into the back of the tonearm, that just adds some weight.
but there is no other bolt or screw that tightens the back of the arm against the rubber plug.

rotating the back of the arm does not do anything but rotate the arm around the plug, no loosening occurs.
I'm reluctant to see if it will pull out.
A service manual might be the order of the day.

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Re: Pioneer PL-550 counterweight ?

Post by ttomt » 20 Aug 2017 23:20

Here is service manual download link https://www.vinylengine.com/ve_download ... ervice.pdf
Not much use as does not break down the arm to that extent.
If you take the s arm off it may screw in through that side, this is the only other way I can think of screw attachment working with no access from the weight side. But warning this is a guess!

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Re: Pioneer PL-550 counterweight ?

Post by Copperhead » 20 Aug 2017 23:24

woodmakesitgood wrote:The end stub does screw into the back of the tonearm, that just adds some weight.
but there is no other bolt or screw that tightens the back of the arm against the rubber plug.

rotating the back of the arm does not do anything but rotate the arm around the plug, no loosening occurs.
I'm reluctant to see if it will pull out.
A service manual might be the order of the day.
There must be something holding the stub in place, I doubt they would have designed it to hold weight just by interference fit. Can you work out how it should be held in place?

Just twisting the stub would not make it screw in, once the screw is loose neither the arm or stub will grab it. It will need a long screwdriver to reach it.

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Re: Pioneer PL-550 counterweight ?

Post by woodmakesitgood » 21 Aug 2017 00:46

hmm, on the back of the arm tube there is a small screw, which seems to hold a tab in place.
Maybe that would allow access to whatever holds the stub in place.
The screw is pretty well buggered though, not coming off without just the right screwdriver.
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Re: Pioneer PL-550 counterweight ?

Post by Copperhead » 21 Aug 2017 01:01

woodmakesitgood wrote:hmm, on the back of the arm tube there is a small screw, which seems to hold a tab in place.
Maybe that would allow access to whatever holds the stub in place.
The screw is pretty well buggered though, not coming off without just the right screwdriver.
That is the part which sits in the counterweight thread, leave it be, all you need to do with that is to make sure the tab protrudes enough to contact the counterweight's "thread". The screw that holds the stub in place is down its centre. Shine a light down the end of the stub and you will see it. Look down the hole properly.

You will, obviously, need a screwdriver long enough, and with a small philips head, to reach it.

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Re: Pioneer PL-550 counterweight ?

Post by woodmakesitgood » 21 Aug 2017 01:13

Copperhead wrote:
woodmakesitgood wrote:hmm, on the back of the arm tube there is a small screw, which seems to hold a tab in place.
Maybe that would allow access to whatever holds the stub in place.
The screw is pretty well buggered though, not coming off without just the right screwdriver.
That is the part which sits in the counterweight thread, leave it be, all you need to do with that is to make sure the tab protrudes enough to contact the counterweight's "thread". The screw that holds the stub in place is down its centre. Shine a light down the end of the stub and you will see it. Look down the hole properly.

You will, obviously, need a screwdriver long enough, and with a small philips head, to reach it.

Right you are sir.
A thin philips head found the screw that connects the two arm pieces, even though my eyes could not.

The screw is bent, which is the reason for the sag.
But it doesn't back out all the way, it is kept from being removed by the end piece which has the tab.
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Re: Pioneer PL-550 counterweight ?

Post by Copperhead » 21 Aug 2017 11:03

woodmakesitgood wrote:Right you are sir.
A thin philips head found the screw that connects the two arm pieces, even though my eyes could not.

The screw is bent, which is the reason for the sag.
But it doesn't back out all the way, it is kept from being removed by the end piece which has the tab.
Finally! The black rubber bung will just be pressed in the stub, you can try pushing it out from the screw head's side, or cut the screw as close to the bung as possible.

Hopefully the bearings in the arm are not damaged, it must have taken some force to bend that bolt.

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Re: Pioneer PL-550 counterweight ?

Post by woodmakesitgood » 21 Aug 2017 17:12

Copperhead wrote:
woodmakesitgood wrote:Right you are sir.
A thin philips head found the screw that connects the two arm pieces, even though my eyes could not.

The screw is bent, which is the reason for the sag.
But it doesn't back out all the way, it is kept from being removed by the end piece which has the tab.
Finally! The black rubber bung will just be pressed in the stub, you can try pushing it out from the screw head's side, or cut the screw as close to the bung as possible.

Hopefully the bearings in the arm are not damaged, it must have taken some force to bend that bolt.
The rubber bung is fine, no need to remove it...but the bolt is pretty bent.
I think trying to cut the bolt would be risky.

Even if I didn't damage anything while cutting, too short a bolt wouldn't fully connect the pieces. The bolt needs to be replaced, but it's tough to get it out of there.

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Re: Pioneer PL-550 counterweight ?

Post by Copperhead » 21 Aug 2017 18:23

woodmakesitgood wrote:
The rubber bung is fine, no need to remove it...but the bolt is pretty bent.
The bolt needs to be replaced, but it's tough to get it out of there.
Yes, but as the bolt sits in the bung, removing that would get the bolt out too.

The plastic (or rubber) will have expanded due to it being compressed by the tightening of the bolt. Seeing as the bolt is bent, the bung is in its expanded state and is semi stuck in the stub.

Push the bolt as far back into the stub as you can and gently remove the bung.

To be clear. In assembly, the rubber bung with screw inserted is loosely screwed
in the arm then the stub is slipped over it then tightened up. You need to reverse the process. This means you can pull the bung out from the visible side, it will not go through the other way.

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