No. 6435
Motor













No. 6435 | Overview | Starting Line | Arrival | Deconstruction | Beneath Decks | First Night's Spin | Listening To Plinths | Motor | System : The Tonearm | Tweaks, Contact | Articles | Bookshelf | Links | More Links | Transit | Next





*
















A few months into having an operational 301 I returned to the condition of the drive-motor and it’s bearings.  What is really simple to grasp turns out to be relatively involved, if only in terms of access, situated as it is directly at the center of the turntable mechanics. 

The motor’s rotation is fixed on it’s axis at two points, an Upper Bearing which serves as a guiding collar to steady the rotation, and a Lower Bearing which not only steadies and centers the rotation, but also serves to support the whole rotor-shaft as well. 

Each is meant to be well coated in electric-motor oil, and kept supplied with said oil via an absorbent felt washer adjacent to the bearing assembly. When the felt washer is saturated with lubricant it provides a reservoir with which to keep the bearing and thrustball coated. 

When I first came to the motor bearings, I reasoned that since motor rotation felt smooth before the lubrication, I could add some additional oil and call it satisfactory.  Well, partly true, but with a fifty year old mechanism it’s all-around better to get in there and clear out the old lubricant, start fresh with a squeaky-clean bearing that you’ll soak with brand new lube….

If it’s the base for the motor’s rotational action, it’s the basis of the turntable’s performance, so there’s every reason to be sure that it is free of any oxidation or debris, and well packed with lubricant. 

 

 

So the next level is to get at the motor's lower bearing and thrustball, for which you need to do the following :

1. with unit unplugged from power, set lever to Off and disengage eddy-current brake via pitch control (ie rotating pitch all the way to "+" moves the brake-shoe away from the eddy wheel & avoids damage when deck is on it's back).

2. do not loosen upper motor bolts, do not remove stepped motor pulley, or eddy-current disc from drive-shaft. You'll be leaving all of that as set by Garrard.
Remove platter and mat. Make sure you protect levers and spindle, and then turn the 301 upside down (use blocks, books, or the plinth to set table on it's back.)

3. pull circlips off the three bottom spring-mount Pins, and then disengage motor from bottom springs by pulling pins. 'Leaning' motor toward the pin/mount you're removing lowers the spring tension and eases the removal process, but don't over-stress other springs--- they can be stretched too much. Also detach AC block from motor

4. remove nuts from bottom-half 'clam-shell' casing of motor

5. in a precise straight up motion remove bottom clamshell. Do nothing 'side-to-side' that could nick or graze motor shaft, or the softer part #99, the Rotor Bearing, while sliding upward.

6. use a lintless rag to "wick out" the bottom bearing. Clean with solvent like lighter fluid the base of the rotor shaft, the interior of the clamshell, and the bottom bearing / thrust-ball, which will benefit from a soak to dissolve any hardened-up lube. Do not use anything that could deposit lint or particulate into bearing.

7. wick out any remaining fluid, solvent, lube and then fill bearing with a light motor oil. I use the '3-in-1 SAE-20 special-blend-motor-oil', (not the lighter ‘household’ 3-in-1) for this, and also for the upper bearing. This also benefits from an oil soak, a wick-out with a clean cloth, and a refill.

8. once complete, reassemble and turn table upright. Gently turn motor manually for a minute or two to get bearing seated and smooth. Start again if it is anything but smooth and freely rotating.

Sounds much harder to do than it is. These are the basics--- keep a clean idler and platter-track, lube points cleaned and re-lubed. This is the start you want to give any 301/401.

One easy alignment trick is to run the table, at least 30 minutes on each speed, before disassembling, so as to clear a bright polished mark on the steps of the pulley.  This will serve as an alignment key when setting the height position of the rotor shaft after lower-bearing service, as below.......

 

 

301_motors_1.jpg

Rethinking  the bushing (#99) + thrustball (#120) + felt washer (#100) + rivetted plate (#121) situation ... I really couldn’t be sure that the thrustball was free and unencumbered. 

I went back yet again to the Garrard manual, which does in fact show, first, that the thrustball is held in place by a concentric spring assembly (#98) --and also, that those elements are on the outside of the aluminum 'clamshell' motor housing and thus pretty well contained for perpetuity by the four micro-rivets that hold the cadmium-plated 1x1" cover, (#121), onto the clamshell exterior.

They're outside of the motor’s clamshell housing. So this little bearing setup is under lockdown unless you go to the extent of drilling out the four tiny rivets and then retrofitting some other fastener on reassembly......

Thus a good procedure is to re-soak and hope to budge a reluctant thrustball, but again only with something non-lethal to the finish of the bearing, washer, or ball... Since I didn't think the elements were damaged, only slightly sticky, I kept at it.

I was not inclined to add any heavy solvent / penetrant, due to that felt washer, which I couldn’t be sure wouldn’t dissolve entirely ----and so I went with a few more oil-soaks and finally a Heated Soak. I just put the whole lower-clamshell-w/bearing on the warm element of the kitchen range for an hour, topped up with the bearing-assembly oil.

Another hurdle is that if you want any 'grip' on the thrustball as you prod it in hopes of turning it, you can't use the same smooth slippery stuff (nylon stick, bamboo stick) I'd been probing with.  After the saute was over, I got another bamboo kabob-stick and deliberately hacked it unevenly across, so the exposed end was somewhat rough and mottled, so as to have some grip. I cleaned up the cut a little with some light sandpaper, and, got rid of any particulate .... and ... this was an all-around better ‘prod’.

And pretty much an immediate success. Whatever was left at the 'rear' of the thrustpad, below the thrustball, just gave way. Just needed a little more traction.

Guess I should emphasize that all I've done is loosen up the thrustball ---- it doesn't come out of the rivetted enclosure, by design. That would be a more elaborate strip-down, to actually access the t-ball, bushing-shaft and felt washer.

I waited for a complete cool-down, then replaced surplus heated-oil with new clean oil and reassembled.....

Something I’ve learned to do by now, with a couple 301’s getting lower-bearing service here, is to Reassemble In An Upright Position.  Which maintains all parts in  vertical relation to each other and allows the least spillage of the motor-oil.  It also slightly pressures that oil toward a complete saturation of the felt washer before it exits upwards, which is the goal. 

Giving the motor-shaft a bit of gentle manual rotation during assembly also helps seat the rotor in the lower bearing, which can be a little more, or a little less time-consuming, depending on the original positioning of the elements involved.  Keeping up a smooth turning motion not only helps the assembly process, but also serves as an early warning if something is amiss with the fit. 

It’s also well worth mentioning that the final bolt tightness for the motor bolts should be done by tightening in the turntable-upright position, and testing / inspecting as you tighten.  The vertical relationship of the parts on the rotor-shaft (ie pulley, eddy-disc, etc) and their partners (idler-wheel, brake-shoe, etc) changes slightly with bolts that are under or over-tightened.  What should be judged in the adjustment is, first, the overall smoothness of the motor-shaft rotation, and second, the positioning of the eddy-current disc, as viewed on edge, in the center of the brake-shoe, which gives an idea of correct placement.  If you have run the table on each speed prior to disassembly, you can also use the bright rings on the motor's stepped pulley to align to the idler.  (This works better on the 60hz brass pulley than the nickel 50hz one which seems to keep a more intact finish.)

This takes a bit of trial and error, but--- if the Upper Motor Bolts have never been loosened or re-positioned, there is, at least, an existing starting mark for the final adjustment of the Lower Bolts. 

 

*

Parts Numbers here are from the 1956 ‘two-star’ Garrard 301 Schedule 1 Manual.

Thanks to Vinyl Engine for providing this online version of the manual, applicable to the greasebearing tables.
















Tweaks

Home