Broken AR XA Armrest Repair

Discussion in 'Turntables' started by 12ax7, Feb 14, 2011.

  1. 12ax7

    12ax7 Super Member

    Messages:
    2,003
    Location:
    Syracuse
    Got one of these?

    [​IMG]

    A common result of trying to remove the lock nut or just aging and flexing is that the threads break off of the plastic armrest. There are options to replace these, such as a rest from a different table, but I wanted to retain an original appearance.

    I got some 5/32"x.014" square brass tube from a hobby shop and some 4-40 thread brass screws, nuts and washers. I chose #4 thread because that is the original size and wouldn't require enlarging the hole in the steel deck although it does fit loosely in the tube (every mod I make to this table is reversible). Cut the tube to 1 5/16" in length. File, sand and polish the rough edges. File or grind the screw head evenly to a square shape to fit snugly in the tube and wrap single strand copper wire around about 1/8" of the thread below the screw head. This will center the threads inside the tube. Flux the screw head and wire, insert into tube and solder in place with a propane torch.

    The bottom of the original armrest and the hole in the deck are diamond shaped to align the rest to the AR arm shape. If you've swapped arm wands, this alignment may no longer be correct. Also, the original armrest was quite flexible, which allowed it to move back and forth with the movement of the soft AR subchassis suspension. I made soft washers out of thin sheet neoprene by using a paper punch and a sharpened section of an old antenna as a smaller punch that allow the new armrest to also flex.

    [​IMG]

    [​IMG]

    Cut the shaft of the old armrest to accomodate the shallower depth of the brass tube. The cross section of the shaft is slightly trapezoidal, so you may have to scrape the wide side slightly to fit. I found that no adhesive was needed to make a snug fit.

    Some sort of threadlocker will be needed. Lock washers won't work if the rest is to remain flexible. That rubbery clear glue from junk mail seems to work well if stretched around the threads and then heated after the nut is in place.

    These can also be used as a dress-up accessory by polishing to match a polished counterweight and logo badge. When painted satin black, you'd have to look twice to tell that they're not original.

    [​IMG]
     
    Last edited: May 23, 2011
  2. beatcomber

    beatcomber AK Member

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    17,416
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    Lexington, Massachusetts
    You are the master of fixing the AR/XA's seemingly unfixable parts. Well done!
     
  3. hatrack71

    hatrack71 distracted by everything

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    5,969
    Location:
    Helena, Montana
    Very nice solution there!!!! I had 3 of these tables at one time and all of them were plagued by this issue.
     
  4. 12ax7

    12ax7 Super Member

    Messages:
    2,003
    Location:
    Syracuse
    Thank you both. As soon as I get some more brass screws I'll post more detailed pics of the soldering process.

    [​IMG]
     
  5. KrisM

    KrisM Addicted Member

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    8,432
    Let me be another to say "thanks". My armrest is fine, but I'm sure I'll come across another table in the future that could use this treatment.
     
  6. clydeselsor

    clydeselsor Lunatic Member

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    10,678
    Location:
    N.W. Indiana
    Awesome job!
     
  7. clydeselsor

    clydeselsor Lunatic Member

    Messages:
    10,678
    Location:
    N.W. Indiana
    BTW: Did you put a different arm tube on the tonearm? I noticed that you have a standard headshell and I didn't think those would work in a original AR arm...
     
  8. reneborg

    reneborg I'm Vintage Too

    Messages:
    1,697
    Location:
    Upstate, N.Y.
    Nice repair job, Gary! It looks great.
     
  9. gkimeng

    gkimeng Forum Mod, ClassicSpeakerPages.net Subscriber

    Messages:
    2,688
    Location:
    Portland, OR
    My early-model AR TT has an armrest that is identical in shape to the later black plastic ones, but is cast in white metal (no springiness at all and it doesn't grip the arm at all when it's at rest). Doesn't seem to have had any problems with the suspension.
     
  10. marcmorin

    marcmorin AK Subscriber Subscriber

    Messages:
    7,942

    I'll speculate that it is a technics arm tube.....I'm not sure which model, but I know some were exact bend/length to the AR XA, XB arm.
     
  11. 12ax7

    12ax7 Super Member

    Messages:
    2,003
    Location:
    Syracuse
    Good speculatin'. The arm wand is from an SL-D2 parts unit (well, it's a parts unit now, right Rene?). The O.D. is the same. The bends are slightly different, as mentioned in post #1, but the collar ends up in the right position. The Technics wand is slightly shorter, which is good because the JIS headshells are slightly longer than the AR headshell.
     
  12. 12ax7

    12ax7 Super Member

    Messages:
    2,003
    Location:
    Syracuse
    You're right, its not really a problem. It's just that I've seen some AR arm wands all scuffed up underneath from moving back and forth in the armrest. I just wanted to minimize that since the plastic armrests do grip the arm.
     
  13. Montycat

    Montycat AK Subscriber Subscriber

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    15,268
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    Well this thread deserves a bump. Not just for how good a tutorial it is, but also because I just made one of these. :thmbsp:

    I'll get pics of what I made later but here is what I started with. Yes it's a wooden block glued to the top plate just ahead of the old rest position with the original (broken) rest in a hole in it. It is really not the worst that could have been done, but I wanted something a bit more svelte.

    [​IMG]AR XA turntable 3 by Buhduh, on Flickr

    I've replicated the design above (from the original post that is) quite closely but rather than soldering the bolt into the square tube I'm going for epoxy. I did solder some wire around the 4-40 bolt though. I will find out if it is secure enough and if not I have lots of the square brass stock and bought extra bolts. I also have to work out the washers too but I think it going to be fine. :D
     
    Last edited: May 30, 2014
  14. macyjrm

    macyjrm AK Subscriber Subscriber

    Messages:
    971
    Location:
    Mississippi
    Thanks for the resurrection. I've got some small pieces of black walnut laying around for which your idea would be a great application. Really nice idea!
     
  15. Montycat

    Montycat AK Subscriber Subscriber

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    Sorry, not quite! I got this table with the wood block, but I took it off to do the brass tube thing.

    Don't get me wrong, I think the wood could look great but I think it should be a lot smaller and in a dowel or cone shape. This block was a cube just over 1 & 1/4" each side and just too chunky. If you have a lathe you could make something really cool.
     
  16. Montycat

    Montycat AK Subscriber Subscriber

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    15,268
    Location:
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    Here it is installed. Taking off the wood black left glue residue behind. That's ok, this table is going to be taken apart, painted and otherwise spiffed up soon.

    [​IMG]AR arm rest by Buhduh, on Flickr
     
  17. 12ax7

    12ax7 Super Member

    Messages:
    2,003
    Location:
    Syracuse
    There ya go. I've rethought the washer/threadlocker thing since first posting this. Of course, using no washer beneath the armrest would give the most authentic appearance, but I still recommend a neoprene/rubber washer above and below the deck for the reasons given earlier in this thread, but now with no metal washer above the deck. The neoprene washers can be cut quite small, even square. Now obviously, you can't tighten the nut too much with the flexible washers and the nut will loosen with use, not good. At this point I think the best course is to double nut the armrest, washers or not.
     

    Attached Files:

  18. macyjrm

    macyjrm AK Subscriber Subscriber

    Messages:
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    Location:
    Mississippi
    Let's not discount that wood block solution just yet ( since it's a much better fit for my talent set). I was thinking of a less chunky block fixed to the metal base by a screw from underneath the base. I knew I kept that busted XA tonearm rest for a reason!
     

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