Mark Anderson came up over the weekend, and we played around a little with a LAB-440 TT he'd be having niggling troubles with. He had installed a new Shure M35s cart on it when he first got it, and wasn't that happy with the sound, plus it had a tendency to have trouble tracking.

Mark left it as a piddle project for me, and this morning I put a Ortofon OM-10 on it just to see if the cart was contributing to the tracking problem. It did wonders for the sound, but didn't help the tracking at all. I've adjusted the weight as much as I dare with no stylus gauge, and still I get repeated one second or so cycles of back-tracking no matter how heavy or light I run it. It always back-tracks, never forward, and it will do so with consistency in the same spots.

Any ideas as to a simple adjustment fix for this tonearm setup? FYI - It is dead stock, and in beautiful shape.

All help, advice, maniacal laughter, and accusatory finger pointing welcomed :)

Fotno

When you move the arm toward the center by hand, does it move freely? Something's got to be keeping it from doing that while on the platter. Rough bearings, cueing not fully releasing, antiskate too high. Hence the always back-skipping.

I don't see how a cart. could ever cause this.

Good Luck.
Doug

Hehe, forgot, does the record have a skip in it? :lmao:

Well Mark didn't think it was the cart either, but I thought since I had a spare handy, it might be worth a try.

The anti-skate has been adjusted up and down to see if would make any impact, none. The arm moves smoothly, with no apparent roughness, or stickiness. I'll try to check the cueing to see if anything hinky is happening, the problem for me is a good deal of TT science kinda loses me in the turns.

Hey Fotno, check to see that the cueing lever is falling all the way down and not interfering with the tonearm. I had a similar problem on mine where the needle would jump back. I found the when I lowered the tonearm it was still pushing up on the tonearm. A quick adjustment fixed it.

Checked the cueing, looks like it's dropping all the way down, and does not interfere with the tonearm. Thanks for the advice Doug, Jimmy, that's one more possibility struck off the list.

Okay, I can't tell you WHY it's doing it, but I can tell you what it's doing. First, in the instant before it begins to back-track the stylus can be observed (looking from above the headshell, stylus pointing away from me) to move from a centered position, to off of center by a fair amount - Think from 12:00 to 2:00 on a clock face towards the center of the platter, and that'd be about right. It then begins to have a slightly fuzzy or distorted sound, and then the back-track happens. It's like the needle is following the track, but the arm is pulling against it.

Could it be that the anti-skate is pulling too hard on the tonearm? Nothing changes if I increase or decrease the amount of anti-skate. Matter of fact, the difference it makes is undetectable. Is it possible that the anti-skate is frozen in place?

Pull the cover off the record player to expose the anti-skate mechanism. It's usually some plastic gears or a gear that looks like a small curve. This curve is what applies the anti-skate, relative to where the dial is set, to the tonearm. It could be that the plastic anti-skate curve is stuck and the anti-skate knob is broken, giving you the idea that it is still attatched.

Also, does the stylus bend like that regardless of what cart you have on? Or is it with just that one cart? If so, it could be a bad stylus.

What about the record? Does it do it with all records or just that one? If it's with all records then does it jump at that exact point? If so then we've ruled out bad records, bad stylus, and bad cart. The remaining culprit would be anti-skate knob. A direct inspection will be neccessary.

Hope this helps Fotno!!

Jimmy

It's consistent with both carts, I've tested it on 5 different albums now (all in VG condition), and the result is the same. It does tend to be worse the closer it gets to the label. But it can happen anywhere on the disc. Anti-skate is looking more and more like the suspect here. I'll PM Mark and see if he minds me taking it apart to find out...

Thanks again Jimmy!

I ask in a state of pure ignorance, but if the arm moves 'in' before moving back, is it possible that the 'return' mechanism is engaging 'way early?

Two more:

Your table perfectly level? Try tilting the table so the arm doesn't
backtrack.

How about the arm itself? Bearings, knife-edge symmetric? If not,
you need to fix the pivot mechanism.

I had both problems on a Weathers many years ago.

I ask in a state of pure ignorance, but if the arm moves 'in' before moving back, is it possible that the 'return' mechanism is engaging 'way early?

I think what he's saying is not that the arm moves in but the stylus tries to follow the groove but the arm won't move with it and drags it back to the previous groove.

You may have hit on something though. If there is too much resistance in the tripping linkage, it will cause this symptom too. I've had it happen.

Of course, I'm not familiar with this table but it is a possibility.

Doug

First things first, the tonearm doesn't move when it backtracks, at least not perceptably. What's happening (at least to my eye) is that the stylus is "loading up" kind of like a spring will when it comes under tension, and when the tension becomes too much, it's releasing that tension by hopping backwards.

I don't have a manual for this table, but I am assuming that it's a bearing mounted tonearm, as it's a sealed system, and it feels like a bearing when I move the arm, and doesn't look like what I think of when I think knife egde systems. I stuck a level on it when I first noticed the way the stylus was loading up, just to make sure it wasn't trying to run "uphill".

FYI - This has been going on since Mark got the table, so that means it's been happening on a variety of surfaces, with two different cartridges, in two different states. All variables have pretty much been eliminated except a mechanical problem with the table itself.

Could it be that the anti-skate is pulling too hard on the tonearm? Nothing changes if I increase or decrease the amount of anti-skate. Matter of fact, the difference it makes is undetectable. Is it possible that the anti-skate is frozen in place?
I'll bet this is it, Fotno. When I change the anti-skate on my Dual, it doesn't seem to make any difference at all unless I'm testing it with a grooveless test disc, even when I look underneath and see springs moving. No matter where I set mine, I always get a one-groove back thing just like what you're getting. I also can't HEAR any difference in settings, either. I just figure that as long as the cart doesn't move when I set it at a certain number on the Shure disc's grooveless band I'm okay. Works for me.
Tom

Thanks for the help guys, I'm in a holding pattern till Mark gives me the go ahead (or the cease and desist:)), to try to fix it. Between everything you guys have suggested, and my own observations (thank you Bill Nye) I think I've got it narrowed down to mechanical resistance at the pivot point, or drag caused by the anti-skate.

bearing problems in the tonearm. Inspect closely to see if this arm has been 'dinked' around with - that's a technical term for someone who tried to play with the pivots. If its not one of the 4-point gimbals then you'll have to start looking underneath the plinth for the bearing race. Look for some sort of locking nut that would control the pressure on that race.

Also, since its always done it for the current owner, there's the possibility that the TT was hit or dropped and the tonearm has sustained damage.

That dance the stylus does, particurlarly on the inner grooves, is the dead giveaway.

Cheers,

David

It might be worth flushing the bearings with solvent, and then perhaps lubing them -- if you get a piece of dust into the bearings, the ball race can get jammed up, but in an unpredictable way. I've had a couple of arms where this sort of thing happened. Cleaning with Coleman fuel and then a bit of WD 40 usually helps. While you are up to it, you might consider damping the bearing with silicone (STP works). People disagree about whether this is a good idea, but Frank Van Alstine suggests it, and I respect his views.

OK, I see where I was wrong before. Question: when you checked the tonearm for free movement, was the arm up or down? There might be something that catches only when the arm is down.

I have the owner's manual for my Lab 440. Troubleshooting info is scant, and what there is doesn't cover your problem - which I agree appears to be a tonearm bearing. If it were unadjustable excessive anti-skate, you should see stylus 'lean' all the time.

Bob

Okay guys, here we go. File this away for future reference on LAB-440 TT's. Here's the missive I sent Mark this morning.

So I started a thread on the 440 (sent you some PM's about it too), just to get some feedback from the turntable boys. In the meantime, I played records, and watched the stylus... Here's where it gets fun. With the Shure, it noticed that when "IT" would happen three things coincided, always.

1 - The audio would get slightly fuzzy.
2 - The stylus would visibly move off center from 12 - 1 O'Clock, Just the stylus not the whole arm.
3 - When it happened, it was always a back-track, and always one full revolution.

So then I changed over to the Ortofon, and repeated listening to the same albums and watching the same way. Here's what I found...

1 - The audio would get slightly fuzzy.
2 - The stylus would visibly move off center from 12 - 1 O'Clock, Just the stylus not the whole arm.
3 - When it happened, it was always a back-track, and always one full revolution.

So at this point I've eliminated two things, common albums, and common cartridges. So now it's down to the machine itself. I absorb what the guys are telling me, and concentrate on it a little further, until I come to conclusion that this is not going to fix without taking the TT apart. So I decided to PM you to ask if it would be okay if I did, and wait on your reply. And I waited about 4 or 5 hours... Until I couldn't take it any more, because I was convinced I knew what was wrong. So I took it apart, and man are there a lot of parts in there... Just kidding... It's actually pretty simple. Here's where it gets really fun.

Once opened, I just sat and looked at it for about a half hour. I do that a lot, helps me to think. Finally after I had stared at it for a while, I noticed that all of the functions (including anti-skate) seemed to function properly with their switches and what-not, so I thought maybe I was barking up the wrong tree. That's when I saw it. Anti-Skate on a 440 works in a really cool, really automotive kind of way. How it works is, the dial actually moves a little rubber brake up against the bottom most part of the tone-arm spindle, right above where the wires emerge and are connected to the circuit board. It didn't take a very long look, and an even shorter touch to see what had happened. The brake is a thin piece of steel, with a rubber pad slipped across it, that can be applied at different pressures depending on how much or how little anti-skate is actually dialed in. Well every thing was working mechanically as it should with one tiny exception. The rubber pad had long ago given up the ghost and had disintegrated into a sticky, greasy mass and collected, in a semi-hard blob on the side of the spindle where it touched (an arc of about 1/3 of the circumference). As the tone-arm went through it's arc of travel, the brake was only rubbing it's bare metal up against a sticky mess of irregular tar-like crap. Long story a tiny bit shorter, I cleaned the spindle and the brake with IPA (I've got a feeling I'm gonna have black fingers for a while) and remounted what was left of the rubber brake material on the metal tab. Buttoned her back up, and hoped for the best.

I've now listened to 6 different albums, and all have played in their entirety without a hitch, they auto returned properly, experinced no skate, and everything functioned perfectly. All of these were albums that formerly wouldn't play completely, if at all. I don't know how long my little repair will last, I have a feeling I need to epoxy a piece of neoprene back onto the metal brake base to make it permanent, I also probably need to get the spindle cleaned up a little better. The IPA didn't cut all the goop off. I thought I'd try some goo gone to get it all the way clean. But for a 30 minute fix, it's working amazingly well.

So at least for now, that's the fix. If you now own, or plan to own a LAB series TT, it would be one of the first places I'd look for potential problems as it looks like disentegration of this rubber bit is pretty likely.

Thanks for all the help guys - By George I think we've got it!

- Fotno

Punkin' head - you are the man! I'll be needing that table back now :D - Mark

Why thank you kind sir, would you prefer UPS, FedEx, or DHL? :D Tell you the truth, I'm just glad I didn't tear anything up! Only you know hopw serious I am about that...

Hey fotno, great work! You are now officially a TT technician whether you want to be or not!

Seriously, nice sluthing. There is always a reason for these things and you found it in this case.

Doug

Hey fotno, great work! You are now officially a TT technician whether you want to be or not!

Seriously, nice sluthing. There is always a reason for these things and you found it in this case.

Doug

Thanks for the words of encouragement Doug, I surely need all of them I can get!:)

Excellent work Fotno! :thmbsp:

Sometimes that's the best way to handle a mechanical issue... just stare
at it a while and look for what's out of place... sometimes it pops right out
at you, sometimes it takes a while! :D

Scott

I've found (for me at least) that if I rush in - It gets real broke, real quick. So I just sit and look at it until I'm sure. Of course my wife thinks I've taken leave of my senses when I do that, but it seems to work.

I like to call it "backwards engineering" :D

Scott

I like to call it "backwards engineering" :D

Scott

Hey, it worked for the Air-Force after WWII!

Good going Fotno!!