Loose shaft on AT6 cycle cam

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klh11
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Loose shaft on AT6 cycle cam

Post by klh11 » 05 Apr 2019 17:07

Do you ever delve deeply into a subject and wish you hadn't? Here's my story...

While doing routine lubing of the idler wheel shaft, motor, spindle bearing, etc. of my Garrard AT6, I decided to look into a minor problem I've experienced: the auto trip doesn't work when playing some 45's. Other records play just fine and there are no other problems with the change cycle.

After watching some videos, I learned to check the trip lever, friction lever, etc. on the main cycle cam...also that some of those cams are jammed onto their shafts and hard to remove. Sure enough, mine was stuck on the shaft and I had to warm it up quite a bit with a soldering iron to get it off. So I cleaned up the trip lever and the friction lever and put everything together...BUT...then I noticed that the cam shaft is loose so that the cam can wobble quite a bit. I've never experienced stalling or jamming with this changer, so when the cam froze on the shaft, years or maybe decades ago, it must have turned freely on its rivet for a long time. Maybe it always turned easily on this particular AT6 and loosened up more with all the rotation.

Is it possible that a cam wobbling on its shaft could cause any problems with the auto trip? Has anybody tried to tighten up a loose cam shaft with super glue or some other method? Was it successful? I've heard from an authoritative source (Adam at dualparts) that some 45's are not manufactured to spec and my changer may not be malfunctioning. Should I worry about the looseness of the cam or just calm down and play my records?

Doug E.

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Re: Loose shaft on AT6 cycle cam

Post by smee4 » 05 Apr 2019 23:42

I agree some 45s don't play well with auto-changers. Particularly later ones. The problem is mainly they don't have enough leadout groove.

Yes, I think the the loose shaft might also contribute to the problem. One tweak, to make an autotrip perform better, is to fine tune the angle of the upright bit on the trip lever that gets pushed back each rev by the lump on the rotating spindle. If the shaft on the cycle cam is loose, I guess that angle can vary a bit.

By the way, a small pencil butane torch works better than a soldering iron for heating bits like this. I had one unit with a loose shaft and never bother to fix it, just used it for parts, but I did consider whether the rivet could be tightened by supporting it appropriately and giving it a tap with a hammer and punch. Not sure glue will work well.

klh11
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Re: Loose shaft on AT6 cycle cam

Post by klh11 » 15 Apr 2019 12:06

Some updates:

-- I did try adjusting the upright part of the trip lever, and I think it helped a lot; a bunch of 45's that didn't trip the change cycle were working after the adjustment. However:

-- I was still bothered by the looseness of the cam shaft, and I tried gluing it without any success. It worked loose after a few days. There's a detailed post on another forum about this problem, and the poster tried the hammer-and-punch approach without much success; apparently there wasn't enough metal at the rivet to tighten up the shaft sufficiently. So, I reluctantly decided to get another AT6 and hope that its cam shaft was OK. I received it a few days ago and am happy to report that its cam shaft is tight and won't turn. Moreover, the cam came off without any problem. I cleaned and lubricated all the relevant points and now have an AT6 that works beautifully. I've already played several dozen 45's, and only one of them refused to actuate the auto-trip. I think I've finally reached "as good as it gets"!

Doug E.

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Re: Loose shaft on AT6 cycle cam

Post by smee4 » 15 Apr 2019 12:47

klh11 wrote:
15 Apr 2019 12:06
Some updates:

-- I did try adjusting the upright part of the trip lever, and I think it helped a lot; a bunch of 45's that didn't trip the change cycle were working after the adjustment. However:

-- I was still bothered by the looseness of the cam shaft, and I tried gluing it without any success. It worked loose after a few days. There's a detailed post on another forum about this problem, and the poster tried the hammer-and-punch approach without much success; apparently there wasn't enough metal at the rivet to tighten up the shaft sufficiently. So, I reluctantly decided to get another AT6 and hope that its cam shaft was OK. I received it a few days ago and am happy to report that its cam shaft is tight and won't turn. Moreover, the cam came off without any problem. I cleaned and lubricated all the relevant points and now have an AT6 that works beautifully. I've already played several dozen 45's, and only one of them refused to actuate the auto-trip. I think I've finally reached "as good as it gets"!

Doug E.
Yes, sounds like it. My AT6 got a workout the other night. Had a party and we spent lots of time stacking old 45s - great fun :)

DSJR
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Re: Loose shaft on AT6 cycle cam

Post by DSJR » 15 Apr 2019 14:58

Only thing with the bad-un may be to tap a thread into the post the cam rotates on and use a screw with spring washer (plus loc-tite) to anchor it? I've never dared attempt this, but maybe a work-around to save scrappage?

klh11
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Re: Loose shaft on AT6 cycle cam

Post by klh11 » 15 Apr 2019 20:34

I've heard of doing that, but I'm not up to such precision work right now since I don't have a proper workshop. You'd have to drill right in the center of the shaft and make sure you're going in perfectly straight. The other thing to be cautious about is that either the link that actuates the record spindle or the trip link passes right under there and you need to be sure there's sufficient clearance for it. Perhaps that's why Garrard used a rivet. (Of course it's more likely that Plessey told them to; the Autoslim mechanism, good as it is, must have been designed with cost and labor savings in mind.)

I'm spinning lots of records today. One strange thing: even though in my new AT6 I'm using the headshells from the old changer with the same cartridges and styli, I swear that everything sounds better. Some sibilance that I had experienced with some LP's from the 70's is gone now. I can't imagine that there'd be that much difference in tracking from sample to sample or that it would be that critical. I'm using a Pickering 380 with a .7 mil conical stylus and I've adjusted the tracking pressure to be the same as it was before.

Doug E.

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Re: Loose shaft on AT6 cycle cam

Post by smee4 » 15 Apr 2019 22:43

klh11 wrote:
15 Apr 2019 20:34
Perhaps that's why Garrard used a rivet. (Of course it's more likely that Plessey told them to; the Autoslim mechanism, good as it is, must have been designed with cost and labor savings in mind.)

The funny thing is, the autoslim mechanism is the one I always find easiest to get working again. It seems to survive the years very well. others can be more canterous, or even (some BSRs for example) damn near impossible to make work properly.

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Re: Loose shaft on AT6 cycle cam

Post by DSJR » 16 Apr 2019 14:02

Garrard (forcibly) cheap-skated everything they could within reason and it's my view that the ingenuity of the design and manufacturing staff that made them such useful and endearing products for the money. If you chuck funds at it, it is easy to get it to be good - Look at turntable systems at £/$ 25k and more to see what I mean. They were allowed? to upgrade parts later on with the large format Zero 100 and 'SB' series of the autoslim however.

The Autoslim mechanism once serviced, is simple, long lasting (also check the riveted 'catch' which locates and holds the main mech plate as it pivots and then 'slides' through this part, as looseness here causes the arm to vertically 'bounce' half way through the cycle) and pretty tough. Garrard were in the habit of riveting posts to the deck plate sadly, even on top models.

I'd keep this bad-un for now, as you may have an opportunity to repair this post (I'm sure it may be possible to find a low-headed screw or bolt to do what I suggested, or modify parts underneath to give the clearance (it's a while since I last took a look).

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Re: Loose shaft on AT6 cycle cam

Post by ianpitts » 19 Apr 2019 15:47

A bit of a cheating repair, but I fixed one of these by MIG welding the post from underneath (with the cam and cartridge removed) and it has worked well since. may be worth seeing if your local garage can tack the post from underneath. My repair has lasted over 5 years.

klh11
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Re: Loose shaft on AT6 cycle cam

Post by klh11 » 20 Apr 2019 03:48

ianpitts wrote:
19 Apr 2019 15:47
A bit of a cheating repair, but I fixed one of these by MIG welding the post from underneath (with the cam and cartridge removed) and it has worked well since. may be worth seeing if your local garage can tack the post from underneath. My repair has lasted over 5 years.
I don't think it's a cheat at all...that idea occurred to me and it seems like a good solution if it works. If I had a small torch I'd be tempted to try it, but I live in a small apartment and simply don't have the facilities for this kind of work. All my mechanical work is carried out on my living room floor. The acrobatics involved are getting increasingly uncomfortable in my old age!

Doug E.

P.S. Now that the changer is working beautifully, I have to deal with the electronic side of the equipment. The AT6 is in a KLH Model Eleven that needs some work in the tone control section. Pots have been cleaned/lubricated but when power is first applied, the bass control is very scratchy and I'm almost certain it's due to those 16uF coupling caps.

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