Pioneer PL610 - PL630 Suspention Adjustment - Acoustic Feedback

After having this problem for a long while and finally finding a cure for it, and letting everyone know of my find, I get told I'm wrong, even though I've been listening for three nights with no problems.

I'm willing to try your foam idea, I'm sure it works quite well. The idea I'm disputing is gluing back together decayed rubber. Ive restored antique electronics as well as antique and classic cars for 20 years. old rubber parts are always a big problem in a restoration. Once rubber has decayed and is dry rotted and crumbling you cannot glue it back together. If you do, I don't see it lasting long. There's a reason they dont recycle old car tires into material for new ones, once it's been vulcanized once, it's done. When rubber is to the point of crumbing and falling apart, it's time for a new part or a creative solution. That's all I'm trying to say. not trying to pick a fight with you or anyone.

platevoltage said:

After having this problem for a long while and finally finding a cure for it, and letting everyone know of my find, I get told I'm wrong, even though I've been listening for three nights with no problems.

I'm willing to try your foam idea, I'm sure it works quite well. The idea I'm disputing is gluing back together decayed rubber. Ive restored antique electronics as well as antique and classic cars for 20 years. old rubber parts are always a big problem in a restoration. Once rubber has decayed and is dry rotted and crumbling you cannot glue it back together. If you do, I don't see it lasting long. There's a reason they dont recycle old car tires into material for new ones, once it's been vulcanized once, it's done. When rubber is to the point of crumbing and falling apart, it's time for a new part or a creative solution. That's all I'm trying to say. not trying to pick a fight with you or anyone.

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The original rubber serves only as a substrate for the RTV in my procedure. The RTV is what provides the functionality, once it has cured. The original rubber can then crumble away completely.

If I had a mold, I would use urethane rubber entirely, which is not subject to deterioration from exposure to ozone in the air. The walls of the original rubber boots are too thin to allow me to make molds that are accurate enough, using methods available to me. If I could, I would manufacture replacement boots out of a special 2-part urethane rubber I have. Until then, I can only do and recommend what I have found to approximate the original performance.

Your original problem is likely your Ikea table, not the TT suspension, and your solution may actually work for that application, but it will leave you susceptible to resonances that will be audible to you over time. It is possible that the original performance was not designed to accommodate such a resonant table under the PL-630. Remember, it was designed as a TOTL table. I strongly suggest that you put your turntable on a surface that can provide it a good foundation.

I do know what I'm talking about. If you are happy with the way the rubber tape works, go for it. However, you will likely be missing some of the performance available with this table. My joy is taking 30+ year old high end gear and making it perform as well as it did originally, if not better. Many are happy that such old gear works at all. However, generally, they are missing out on what they could have if the gear was not limping. There is a difference between working and performing.

The PL-630 is worthy of a cart up to the range of around $800. But not with a resonant table beneath it, and a compromised suspension system. Again, you can put a PL-630 on top of a set of decent speakers and crank them, and have no acoustic feedback issues. With any configuration, performance will only be as good as the weakest link. The gear you have pictured is worthy of being allowed to produce the best sound it can.

Rich P

platevoltage said:

Do you buy vinyl from Sach in the old McCrones on the weekend? I'm generally always there sometime between noon and 1 on Saturday.

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No I'm not aware of Sach's. i use to buy from the guy who ran Purple Frog records but I heard he closed down a couple of years ago.............

Soooooo, where would one get yellow upolstery foam??

day67 said:

Soooooo, where would one get yellow upolstery foam??

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Generally, there are stores that sell upholstery fabric. I have one almost around the corner from me. You might try a regular fabric store and see if they have any, or know where to get it.

Enjoy,
Rich P

Rich, that makes more sense now. So what you are describing is using the old boot as a former and completely encapsulating it in silicone to basically form a new part.

I'm willing to fix this the right way. I don't have any of the original boots left because they were so bad I swept up the pieces with the vacuum cleaner.

I have my own lathe and milling machine and machining expirience. I'm willing to make a mold for these, but I dont have any good dimentions for a boot. Do you have an intact boot that you can make measurements of and draw me a print?

The other thing is the material. These would have originally been done by some sort of injection molding proceses. If I make a mold it will be an outer section and an inner core so whatever material we use will have to be able to flow well.

I've had experience in the plastic extrusion industry but that is completely different from injection molding, so any suggestions on how the mold should look are welcome. I'm thinking a section with the profile of the outside and another section with a profile of the inside that would bolt together. This won't be very hard to make but injecting or getting the material into the mold will be another story.

Mark

platevoltage said:

Rich, that makes more sense now. So what you are describing is using the old boot as a former and completely encapsulating it in silicone to basically form a new part.

I'm willing to fix this the right way. I don't have any of the original boots left because they were so bad I swept up the pieces with the vacuum cleaner.

I have my own lathe and milling machine and machining expirience. I'm willing to make a mold for these, but I dont have any good dimentions for a boot. Do you have an intact boot that you can make measurements of and draw me a print?

The other thing is the material. These would have originally been done by some sort of injection molding proceses. If I make a mold it will be an outer section and an inner core so whatever material we use will have to be able to flow well.

I've had experience in the plastic extrusion industry but that is completely different from injection molding, so any suggestions on how the mold should look are welcome. I'm thinking a section with the profile of the outside and another section with a profile of the inside that would bolt together. This won't be very hard to make but injecting or getting the material into the mold will be another story.

Mark

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The problem is not the mold, although that is a significant issue. I can have molds made out of metalized stereo-lythic material.

Due to the cross-section, what is needed is at least a tri-partite mold. The real problem is that, since the resulting boot walls are so very thin, injection of the rubber will have to be done at some serious pressures.

Now molds for the boots for the PL-518...that would be another story entirely. Those boots actually hold the feet on the TT. That too would be a tri-partite mold, but the walls are significantly thicker, allowing injection at much lower pressures...a project that has been on my plate for years ( I do have a cross section drawing for that)...

I have access to a nice 2-part urethane rubber, available in various durometers and colors, where the 2 parts are mixed at around 50-50 ratio, unlike most rubbers of its type, requiring a few drops of catalyst per pint. It also comes in small quantities. This stuff is nowhere near as sensitive to mix ratio as the others. It is intended for mold making, but works well for rubber part fabrication. I'm sure you come up with the need to fabricate replacement rubber parts for antique cars all the time. If interested, I can send you a link.

I do not have an intact sample of a PL-630 boot to slice apart and develop a cross-section. I will remember you if I find one in one of my PL-630s, near term.

Enjoy,
Rich P

Rich,
send me the link to the rubber you've found.
I'm thinking of a simple mold and using a modified grease gun for the injection.
I don't know if it will work but I'd be willing to give it a try.
even if the boots are close, would be better than nothing. If you have basic dimentions on one, that would get me started. I may have a shard of one left on the bench to measure the thickness.

platevoltage said:

Rich,
send me the link to the rubber you've found.
I'm thinking of a simple mold and using a modified grease gun for the injection.
I don't know if it will work but I'd be willing to give it a try.
even if the boots are close, would be better than nothing. If you have basic dimentions on one, that would get me started. I may have a shard of one left on the bench to measure the thickness.

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Great stuff, guys! That proves that "necessity is the mother of invention"!

platevoltage said:

Rich,
send me the link to the rubber you've found.
I'm thinking of a simple mold and using a modified grease gun for the injection.
I don't know if it will work but I'd be willing to give it a try.
even if the boots are close, would be better than nothing. If you have basic dimentions on one, that would get me started. I may have a shard of one left on the bench to measure the thickness.

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Here's the link: http://www.smooth-on.com/

I have not looked into it, but I see that they now have a spray-on rubber. That will likely work better than smooting on RTV with a small spatula.

I do not have an intact boot for measurement at this time. I will keep you in mind when I dig out my next PL-630. I have already pieced the boots together on the one I have on my bench right now, and coated them in RTV. I can't get measurements off of them in this state.

I do not believe you will be able to produce the necessary pressure with a grease gun, for this task. The thin walls of the boot, and the viscosity of the un-cured rubber will likely result in voids in the resulting boot walls. You are free to give it a shot, and report back. I hope it works. If so, You can be my supplier...

Enjoy,
Rich P

Hi Rich,
I'll look at thier products better tonight. What kind of shore hardness do you think we are looking for?

RE: the grease gun idea, even the cheapo $15 ones are rated for 5000 PSI
http://www.sears.com/shc/s/p_10153_12605_SPM199562676P?prdNo=21&blockNo=21&blockType=G21

There are a few models good for up to 8,000 PSI so I feel it would work fine.

The only real problem in my mind is the cure time vs pot life of the material.

With one mold, it will be a real PITA to make one boot and then have to clean the gun because the cure time will exceed the pot life on any of the materials I've seen. Plus I really dont know how well this material is going to clean up and what you would even use as a solvent to clean the equipment with.

As far as the urethane tape goes, you were right, it was too stiff.

I tore it all apart again last night and removed all of the tape.

The only thing I used the tape for was the one big coil on the spring that fits underneath into the spring retainer. I split a 5" section of tape longwise and wrapped the big coil. This provided a smooth rattle-free fit into the spring retainer.

I then replaced the springs and wrapped them externally with 1/2" thick sections of "memory foam" from one of those fancy foam pillows. This foam has the consistency of fresh angel food cake. I did about three good wraps around each spring (like a cinnamon roll) and retained them from un-winding with some fine copper wire.

This is the best it has been so far!

It is amazing how the suspention effects the sound on this table so much!

I played some Count Basie last night and he never sounded so good. When you can hear the crispness in the horn section over the bass, you know your getting somewhere in the quest for quelling bad mechanical harmonics!
The other big test for me is Supertramp "hide in your shell" That song contains all sorts of sub-sonic bass harmonics.

I think there is room for improvement though, I'll try to get the Lack table filled with foam this weekend.

I'm still interested in making soom rubber boots, I'll have to do some more research though.

Thanks for everyones input.

Mark

Bringing back the dead. Couldn't stand the suspense any longer so I put it on the kitchen counter and gave the rubbers a closer look and they are in very good condition. Would a coat of the spray on rubber be a good idea to help slow degradation? Put some teflon tape on the plastic threads, spun the adjusters 1/2 way down, installed the bolts. Flipped it over and the suspension feels great. Leveled the platter with some shims and now I await the 103r.