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ARXA damping question?

Thanks for that.

Ok, after several applications of acetone over a two hour period I still couldn't break the screw loose. So, I used a Dremmel with a cutting disc and cut the pesky pin out in place. That made a big difference. The arm pivots very freely now. The brass barrel and the housing move together as though they were one.

Next question. I removed the platter and there is what is left if some kind of bearing washer on the boss that the platter sits on. It is black and somewhat sticky. Obviously this needs to be cleaned off but I don't know what to replace it with. Nylon, brass? What is left of the original looks like some kind of rubber or foam that has descintegrated.

I haven't gotten as far as inspecting the motor yet but wonder if it can/should be lubed.
 
That was a foam washer, and it was a seal to help keep dirt from migrating into the bearing well. Nothing rides on it. You can just clean off the debris and run without it as long as you keep your listening space clean and keep dust from accumulating under the platter.
 
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Thanks. I did just notice that nothing contacts that seal. the point of the shaft contacts the bottom of the bearing well. That material is pretty firm so I think I'll leave it alone rather than risk getting any in the well.

Anything else that should be done to this table? It's pretty clean and I don't think it's necessary to completely break it down.
 
more rotted foam

When new this was more of the be d#$$d foam. This seemed like it was a effort to seal the bearing shaft -sorta unique to this design - attacked a problem that apparently does not exist.I would just clean this off and be done with it, Clean the platter shaft and bearing well . .All of this needs to be cleaned out (91% alcohol ) ,inspected and relubbed and reassembled.I did a bunch of XA/XB's - but haven't touched one in about 20 years. Never encountered a damaged thrust plate ( white nylon?) on one of these - but once cleaned out -given the age - I'd shine a nice bright flashlight in there and see what the thrust plate looks like .
On the arm I would leave the white plastic/nylon washer in place. Another inspection point is the nylon rings that the vertical needle bearings ride in - I encountered a couple of these that were obviously pretty wacked about--notched - you have to think about whether this is going to improve things- at the age these things have reached - there's stuff that used to move that may just want to stay where it is after 40 years in place - but was able to slightly rotate these to but a smooth section under the needle bearing -rest of it doesn't count..Packaging from the factory came with the arm laying on it's side so that vertical slamming during shipping wouldn't damage these.
Great table -Kalishinkov tolerances -I gotta believe that the folks who designed this would be gobsmacked to realize we are still using 'em 40 plus years later.
 
JohnMac said:
Thanks for that.

Ok, after several applications of acetone over a two hour period I still couldn't break the screw loose. So, I used a Dremmel with a cutting disc and cut the pesky pin out in place. That made a big difference. The arm pivots very freely now. The brass barrel and the housing move together as though they were one.

Next question. I removed the platter and there is what is left if some kind of bearing washer on the boss that the platter sits on. It is black and somewhat sticky. Obviously this needs to be cleaned off but I don't know what to replace it with. Nylon, brass? What is left of the original looks like some kind of rubber or foam that has descintegrated.

I haven't gotten as far as inspecting the motor yet but wonder if it can/should be lubed.
Click to expand...

Awesome news on the pin. I was going post and tell you to go at the screws with a hammer drill. That way you would completely mess it up and then have to upgrade the arm. I could then call dibs on your headshell.:D
I'm not sure if you've come across it yet, but there is a thread on VE about polishing the spindle. Since you are working on the platter you might want to inspect it and decide to polish the spindle. Another easy and cheap tweak.
As for the motor, how is running? Is reasonably quiet? Mine was completely seized so I oiled the hell out of it. I've also read about people running it in an oil bath, but I'd assume that was for really noisy motors. With the outer platter off you should be able to drop some oil where the spindle comes through base. My motor is a little noisy. Sometimes oil helps, sometimes it doesn't.
I cleaned the leftover washer goo and then left it. I might try and make a washer in the future, I might not. I don't think it makes much of a difference. I'm sure some would disagree with me.
What are you going to use for a mat? Mine had a nasty, gooey mess of a mat. It was like tar. I experimented with mats and have been using a fairly light mat that came off of a Micro Seiki table. I also tried some heavier mats that were on a couple of Sony parts tables I had. They messed with the suspension too much. Just something to keep in mind if you are buying a mat.
 
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stonedeaf, I don't have a parts diagram. Could use describe "the nylon rings that the vertical needle bearings ride in" and "the thrust plate".

Interestingly, there is still nice clean oil on the platter shaft and in the well. I will however clean is out and replace it. Due to the fact that is has always been wet with oil I don't think any polishing is necessary. I believe that tis table has never been out of service for very long and was obviously maintained.

KrisM, yeah I had considered a hammer drill too but...

There is a little noise when running but I haven't determined if it's the motor or something else. I'll run it with the platter of to see if I can tell.

Not sure about a mat yet. I tried a rubber one off of something else and as you experienced it was too heavy. Maybe cork or felt.
 
Since it looks like stonedeaf has logged off, I'll take a guess at what he was referring to. He can correct me if I'm wrong. At the bottom of the spindle well, and the arm well, there was a little plate that they rode on. I think it was made of Delrin. They can wear out, or be lost. Apparently replacing them can improve the table, although I can't say because I haven't done it. On the platter there should be a ball bearing that rides on this plate. On the platter spindle the bearing is attached. The ball bearing in the arm well is loose. Mine was missing.
Good news on the table being maintained. Mine was obviously left for years. When I polished the spindle it was night and day smoother.
 
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Thanks for that info. Very clear what to look for.

When I spin my inner platter with the belt disconnected it seems like it will go forever so I'm fortunate there.
 
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The bearing screws on my ARXA were tight as well, I believe some thread locker was used. So, I used a technique that I use frequently to unstick bolts in old cars: heat.

I have a butane lighter that I use for cigars. The type with the blue flame. I don't think a regular zippo or the like will work, as the flame won't be hot enough.

Just 30 seconds or so on the screw was enough to break it loose. There is no discoloration of the housing around the screws from this technique.

Oh, and be careful not to burn yourself or your house down!
 
The Delrin thrust bearings are nearly transparent and you may think that there's nothing in the bearing wells. Take a closer look. They can also be a bit tricky to remove. I put a reverse curve on a pick so it wouldn't scratch the babbit walls of the bearing well. Stand the bearing on end with the pick and then use mini needlenose pliers to pull them out. The crossword grid shows how transparent they are.

picture.php
 
audiojones said:
...You are so fortunate to have that overhang gauge (the plastic thing that says "aim toward pivot"). That thing is impossible to find, and it is makes the cartridge overhang adjustment so easy...
Click to expand...

They're easy to make. I took some sheet plastic sign stock and cut it to size. Cut a V-notch in one end for the tonearm spindle (no more "aiming") and scribe the center line, the spindle line and a 15mm line. Drill out the platter spindle hole and place a piece of split hose over the spindle to raise the gauge up.

picture.php


In case I change my avatar, here's a pic of the gauge in use with a different table that also used a 15mm overhang.

picture.php
 
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Thanks Gary. I did see the Delrin thrust bearings in there. It looks like they are in position so is there any reason to remove them?

The wells and shafts appeared quite clean but I cleaned everything anyway, then polished the shafts. That did remove a little darkish krunk that I didn't notice before.

I pulled the bottom. The rubber on the suspension springs is supple. The foam is not so good but still intact.

I can see the bottom of the motor shaft coming through the housing. is that excess for oil or is that sealed. Do I need to remove the motor to oil it or maybe it is sealed doesn't need to be oiled. It is very silent.

I noticed that the motor vibrates with the switch off. Is this some kind of starter? If so I wonder if that could be or should be disconnected. Doesnt seem like a good idea to have juice to the motor 24/7.

I tried some heat to the screw to no avail so I'll call that good for now and move on.
 
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verical bearings

The arm has needle (bearings ?) on either side of it - these are the vertical bearings and ride in a pair of holes on either side of the arm pivot ( the piece that the couterwieght shaft and arm tube both fit into) -there are some nylon/delrin "washers" in those holes - the arm will work without them - but you then need to be very careful when moving the table to not subject the arm to any vertical forces that would flatten portions of the needle bearing .Without the washers you probably will have some increase in vertical friction - just don't know how to source replacements ?
Personally -would inspect but probably not remove the thrust plates under the arm and platter - these are pretty lightly loaded (especially the arm) -So if you've got good lubrication on the platter bearing - it's extremely unlikely they'll be damaged.A missing horizontal arm ball bearing would be a big deal on this arm - that's not a optional part.
Noise could very likely be a slack belt scraping the bottom or top of the motor pulley. Belts lasted a long time on this design - again light platter meant they weren't being highly stressed - but at this late date replacement ( and a spare) would be a real good idea. Does anyone know from firsthand experience a source for these belts that really does fit this table ? I'm beginning to get a bit frosted by running into generic "replacements" whose main virtue appears to be they won't fall off - but clearly bear only a superficial resemblance to the OEM belt.
 
It's "normal" for the motors to vibrate slightly with the switch off. You could plug the table into a switchable power strip. Sometimes the motors can make noise when running without a drive belt too. Oil from the top.

I just wanted the Delrin bearings out to inspect them and to thoroughly clean the wells.

That suspension foam is something I'm still experimenting with. Too much damping? Not enough damping?
 
capacitor

motor vibration when off might be a bad capacitor - look and see if ones hanging off the power switch?
BTW - butane lighter does the trick -but as was posted - you need to think about what else is going to get hot. A small temperature controlled soldering iron will also help melt old or overenthusiastic. applications of lock tite. Use the tip dry (no solder on it).
 
Shouldn't the switch completely open the circuit regardles of the cap? I'll check the value to see if I have a replacement.

I do have my systems on power strips to save wear on the switches in my old gear so it's not a big issue. Just wondered if it was normal.
 
The vertical pivot "bearings" is actually a one piece Delrin rod that goes through the brass pivot drum. One problem with that design is that the drum can shift sideways on the rod, leaving one needle screw riding on the brass drum and the other screw mushrooming the exposed Delrin rod.
 
cap will have shorted

Value isn't terribly important - just something close should do it , Can't say i remember this as a XA problem years ago - but have run into it on a couple of other AC synchronous motors over the years.
 
Quote from the AR Manual:

"NOTE: A small amount of vibration can be felt on the motor pulley even with this switch in the "off" position. This is entirely normal, perfectly safe and no cause for concern."
 
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