Help setting up JMW tone arm

It's a unipivot arm. They all act like this. If it continues wobbling when you play a record, there's a problem. Otherwise, just enjoy it. Good luck, Dave.

Just make sure the pointy thing is resting in the middle of the cup. There is a slight joint edge inside that the point may catch on.

I have a Dual 1019 and a Miracord 50H (both 1960s vintage designs) whose arms rotate on "ball race" pivots, i.e., ball bearings captured in a circular trough. I think the vertical movements are "gymbal" pivots, based on horizontal needles squeezing pits. Too tight is bad, and too loose is bad also. I used to check for the latter by looking for "play" or wobble. The challenge was always to provide arm support and directional guidance while keeping friction as low as possible.

I also have two VPI tables with Graham arms, unipivots like your JMW 9. At first, I had a hard time getting used to the idea that the whole arm rested on one vertical point ("needle?") pressing into a pit in a cup. The only things that kept the arm from flopping over were the weights and geometry -- balance, if you will. Yes, there is a lot of play. But the point does stay in its pit in the cup, and friction is minimized since there is only one point of contact. The stylus is properly positioned as it plays across the record. An admirable achievement!

It's worth mentioning that two other designs have also succeeded in minimizing friction: the Well Tempered Labs Arm (suspended by a thread) and various magnetic suspensions I have read about but cannot remember manufacturer names.

I did not notice wobble during play, just while moving the arm. If it's normal I can live with it. Never had a unipivot arm before. Now I just waiting on a stylus force gauge so I can set it up.

Steve

Oh one last question, how does one adjust the arm lif.It doesn't seem to lift high enough to raise the arm from the record.

Steve

I don't have a JMW arm, but I saw a set screw for the cueing assembly in one of the pictures. This set screw was just to the right of the cueing assembly and just above the cueing lever, screwed horizontally into the supporting member. Perhaps if this screw were loosened, you could raise the entire cueing assembly to the desired height. I hope someone that has a JMW arm can provide a more definitive answer.

Jameswei is absolutely correct. Dave

Steve,
If you don't think you've got it right, call VPI and talk w/Mike. He is a really nice guy, and will be able to help you. Cheers,
Spencer

This set screw was just to the right of the cueing assembly and just above the cueing lever, screwed horizontally into the supporting member. Perhaps if this screw were loosened, you could raise the entire cueing assembly to the desired height.

This did the trick. Thank you.

I actually have a JMW9 setup question, and instead of starting another thread I thought I'd tack it onto this one. I recently set up a JMW9 on a Scoutmaster too, and the other day it started having strange grounding problems. The arm hums when I touch it, and more distractingly, makes loud "thud" noises when I put it down on a record (sometimes even when it's not playing). Would anyone happen to know what's causing this? Thanks in advance.

Not having a JMW 9, I can only offer my generic response, which is that it sounds like either (1) something went wrong with your cartridge internally, or (2) one of your tonearm cables has suffered a short to your arm tube.

To check #2, I would visually inspect the tonearm cabling between the cartridge and the tonearm, to make sure there is no inadvertant metal to metal contact. Also, I would wiggle the tonearm cable at the back of the tonearm (the one that supplies the antiskating compensation), while holding onto the arm so as to generate the hum you described. If the wiggling of the cable causes the hum to disappear and reappear, then there may be something wrong with that cable or its connectors.

To check #1, I would switch cartridges, if possible. If the problems go away after you switch to another cartridge, be sure to switch back to see if the problems return. (If the problems don't return, then maybe the cartridge is OK, and it was just a matter of a tonearm cable shorting out somewhere.) Good luck.

Thanks for the advice. I've switched up the cartridges and the problem has disappeared. So it looks like it's the cartridge. I'l try re-installing it and see what happens.