-edible zone-
No.6435
Overview Starting
Line Arrival Deconstruction
Beneath Decks
First Night's Spin
Listening to Plinths
Motor
System:The Tonearm Tweaks
Articles
Bookshelf Transit
*
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.......
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
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