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Old 14th May 2018, 4:17 pm   #1
valveaudio
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Default Help with Garrard motor

I have Garrard turntable, not sure of the model it could be a AT6 or a 3000. It has no i.d. since it was specially made for KLH in USA. I have taken care of the pulley change and am running it off 120v (its not tapped 240-120v).

The problem is that the 'balance washer' which is attached to the armature has become detached, there is no evidence of where the adhesive parted company. The question is, how can you reattach this in the correct position to eliminate the vibrations I now have. Is there some known technique or is it trial and error? I have tried attaching with double sided in a couple of positions without much success.

Trevor
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Old 14th May 2018, 4:31 pm   #2
Edward Huggins
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Default Re: Help with Garrard motor

It might help if we knew if this was a KLH badged verison of the AT6 or the 3000? I think from memory that the AT6 will have a better quality motor, the same as that in the early Garrard SP25s.
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Old 14th May 2018, 4:54 pm   #3
valveaudio
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Default Re: Help with Garrard motor

The motor has 2 field coils which I think makes it a 4 pole, so probably an AT6. Another thing that complicates the i.d. is that Garrard seem to have fitted an unusual arm, it is has a very narrow head shell.

Trevor
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Old 14th May 2018, 5:32 pm   #4
valveaudio
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Default Re: Help with Garrard motor

Looks like the one here:

http://audiokarma.org/forums/index.p...e-help.782429/
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Old 14th May 2018, 8:20 pm   #5
Audio1950
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Default Re: Help with Garrard motor

The one in the link is a mixture of the two decks in question, but nearer a 3000 than an AT6. Although the headshell is pure KLH, and not the usual 3000 model, the overarm is definitely AT6. So what motor is fitted we still have to find out.
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Old 16th May 2018, 7:27 am   #6
GP49000
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Default Re: Help with Garrard motor

Can you show us a photo of the motor's rotor that has come apart, including the loose part?

On late Garrard 3000s built for KLH, the Synchro-Lab motor was fitted. Some samples of that motor had a defect due to improper curing of the adhesive that was used to bond the grey, permanent ceramic magnet ring to the squirrel-cage section of the rotor. The adhesive bond would fail and the magnet ring would fall off. By seeing exactly what you have, we can identify it. Putting it back properly is another matter.

The AT6 overarm was fitted to certain production runs of the 3000 for KLH, and the narrow tonearm head was fitted starting in midproduction for KLH, replacing the standard 1/2" mounted Pickering cartridge with a plug-in one.
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Old 16th May 2018, 10:10 pm   #7
valveaudio
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Default Re: Help with Garrard motor

Thanks for that, photos tomorrow, Thursday.

Trevor
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Old 17th May 2018, 11:33 am   #8
valveaudio
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Default Re: Help with Garrard motor

Here are the photos. Its a KLH Model AM24 with Garrard TT as shown.
The problem is that the washer that is drilled for balance has become detached from the ring magnet (the magnet is still attached to the armature).
There is no evidence as to the position of the washer relative to the magnet/armature. The adhesive you see is double sided tape I used in an attempt to find the correct position (unsuccessfully) for the washer.

Thanks
Trevor
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Old 17th May 2018, 12:09 pm   #9
Edward Huggins
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Default Re: Help with Garrard motor

This does not help your motor problem, but in terms of your deck ID query, this unit looks hybrid Garrard 3000 with the same tubular tone-arm, but a different headshell. And that motor still looks like that used on the AT6/SP25.
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Old 17th May 2018, 2:03 pm   #10
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Lightbulb Re: Help with Garrard motor

Trevor, the balance washer is drilled making it lighter where the drilling has been done. Line up these drill marks with the heaviest side of the armature and you will be balanced.

How do you find the heaviest part?

Looking at the pictures, you need to get two edges with low friction parallel and level, they don't have to be perfect.

Place the armature on the edges and let gravity find the heavy spot (it's at the lowest part!).

Mark the lowest spot with pencil, then turn the armature to face the other way and mark the low spot again.

In-between the two marks is the true heavy point and this is where the balance washer drill holes should align.

I've eaten the olive, it was lovely!
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Old 18th May 2018, 5:18 pm   #11
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Default Re: Help with Garrard motor

I was thinking about this and wondering if I could remember how to do a single-plane balance, and what I would do if I didn't have an accelerometer. I remembered a colleague who went to balance a big gen-set in India many years ago, and came back telling us the engineers there were using record-player cartridges with styli in, upside-down (accelerating the cart, with the needle responding due to inertia) as measurement transducers! Well, you have one of those, so if there is too much stiction in the thing for Ken's approach to work, have a go at this.

To get it right first time you need a tacho mark - perhaps you can think of how to lash something up optically, but I don't know what you have. Set the tacho up into one channel of a 2 beam scope, and put your cart output into the other channel. Run it up and look at the phase angle between vibration and tacho pulse, and rotate washer to suit - test to ensure vibration is minimised.

If no tacho, no problem - tack the washer on, mark it, measure vibration, and inch it around (making notes!) until the vib signal is a minimum. Let us know how you get on!

cheers
Mark
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Old 20th May 2018, 6:29 am   #12
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Default Re: Help with Garrard motor

That is a Synchro-Lab motor.

Usually when those failed, the magnet ring came loose from the induction armature section. Perhaps there was more heat generated in the induction motor core, causing that joint to fail first? That was a factory error...One of the heating elements used to cure the epoxy adhesive was not working, unknown to the technicians.

You already have looked for adhesive residue that you could match up between parts and, it seems, couldn't find any.
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