LGP-30 Memory Drum Update

Brian L. Stuart blstuart at bellsouth.net
Tue Jan 3 13:47:43 CST 2017

On Tue, 1/3/17, Cory Heisterkamp <coryheisterkamp at gmail.com> wrote:
> What I’m wondering is if anyone is familiar with the setup/adjustment
> procedure for getting the heads set correctly. There *might* be a couple of
> unused tracks I can relocate heads to, but my thought is that if half a
> dozen heads were already in contact, then the rest may be perilously close
> as well (swelled drum?). My odds of setting 71 heads perfectly on a 50 year
> old worn drum is…well…not great.

A while back I read a procedure (probably in reference to the G-15).
Quite frankly, it scared me a little, but I'll pass it on.  The idea is to
use sound.  The tech would use a screwdriver as a sounding bar
between the casing and his ear.  Then the head was tightened down
until you could just hear it start to brush.  I don't remember for sure,
but I'd have to think that you would then back off just enough for
the brushing sound to stop.  I don't recall whether the article said
that this was done with the motor running or the drum was being turned
by hand, but if it were my machine, I'd set the heads turning the drum
slowly by hand and then check for any brushing sound when the motor
comes up.

Whether or not the drum is restorable, I'd still plan on building a drum
simulator.  That way you can get the rest of the machine up and
running without stressing or depending on the drum too much.  Plus
if the drum does turn out to be unrestorable, you'll still be able to
run the rest of the machine.  As to how to approach the simulator,
I would have to think a C.H.I.P. or a Pi would have plenty of horsepower,
especially if you drop Linux and either run on the bare metal or
as an in-kernel driver in something lighter weight.


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