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mechanical friction system, and in all direct drive turntables (except the Sanyo<br />
VDR3000), braking is achieved by reversal of the drive coil magnetic fields.<br />
Failure of the turntable to spin down in a timely fashion could be due to a weak<br />
mechanical friction system, or in the case of reversed coil braking, could be<br />
due to increased friction in the turntable mechanism. At first though this seems<br />
contradictory, since increased friction halts motion more rapidly, but remember<br />
that increased friction also generates more heat, and heat destroys magnetic<br />
fields. While a disc is being played, the Hall Effect transducers near the<br />
magnetic ring on the turntable create feedback that forces the mechanism to spin<br />
the turntable at 450rpm. If there is excessive friction, the magnetic coils draw<br />
more current to maintain the rate, which in turn produces more heat, requiring<br />
even more current, etc. At the end of play, this excessive heat causes the spin<br />
down phase to take longer.<br />
Here are areas to look at to eliminate excess friction:<br />
(1) Turntable height-- needs to be high enough so there is no friction with the<br />
surrounding base.<br />
(2) Turntable warpage-- Never hit a <strong>CED</strong> player while the turntable is spinning.<br />
The turntable is very susceptible to damage from the impact while its spinning.<br />
The reason I mention this is that I've seen <strong>CED</strong> players (and computer hard<br />
drives, for that matter) that won't spin up unless first given a tap. In the<br />
case of <strong>CED</strong> players this "stiction" condition is often caused by a turntable<br />
shaft that was mistakenly greased (see item 4).<br />
(3) Missing Thrust Plate-- J and K players have a small 1/4" plate under the<br />
turntable shaft that is often missing. Sometimes a missing plate can be found<br />
attached to the turntable magnetic ring, since it fell out during a previous<br />
turntable removal and was drawn to the ring.<br />
(4) No Lubrication-- The turntable shaft should be lightly lubricated with<br />
sewing machine oil. Avoid using motor oils (too thick and detergent content), as<br />
well as 3-In-1 Oil (vegetable oil content).<br />
Even in the absence of excessive friction, the rate at which the turntable spins<br />
down varies slightly each time the reject or unload button is pushed. This is<br />
because coil reversal can be initiated in any one of four states depending upon<br />
the particular instant the button is pushed. It's preferable to allow the player<br />
to initiate the reject sequence at the end of play, but in any case, the raised<br />
outer rim of the disc protects the grooves, and with Hitachi players, the small<br />
diameter turntable only contacts the raised center section of the disc.<br />
--Tom Howe<br />
------------------------------------------------------------------------<br />
Date: Fri, 07 Mar 1997 01:51:30 -0500<br />
<strong>From</strong>: Ed Ellers<br />
MIME-Version: 1.0<br />
To: ceds@teleport.com<br />
Subject: An oddball model - SGT101<br />
I have the instruction manual (only) for an RCA <strong>CED</strong> player identified as<br />
the SGT101. As best I can tell it's identical to the SGT100, but page
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