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MMD > Archives > August 1999 > 1999.08.08 > 06Prev  Next

Installing 3-Speed Motor in 78-RPM Phonograph
By Andy Taylor

Hi,  While restoring my Philco console, I ended up with two M4
phonographs.  One was restored and put back in the Philco.  This
is neat.

The other M4 had no motor and no cartridge, after cannibalizing it
for parts for the other one, I decided to try an experiment with it.
(If I destroyed it, I would still have the other one.)  My goal was
to convert the M4 parts phono (78 RPM only) to three-speed operation
with a modern cartridge, while still looking original as possible.

Digging around my parts bin, I found a old modern type three-speed
phono.  I measured the idler wheel, and motor shafts, and sure enough,
they were the same size.  I removed its motor base and idler wheel
(with the three-speed shifter), and installed it in the base of the M4
turntable, making sure that the idler wheel was in the same place as
the original one was.  The base was smaller so I used large clamping
washers to install it in the M4's base.  The M4 had a string coming
from the 'off' switch, that pulled the idler in neutral when the phono
was off.  The replacement motor base had this feature too; it was only
a simple matter of hooking up the string.

I installed the turntable wheel, and powered up the motor: it worked in
the 78, 45 and 33 RPM positions.  Great.  I now had to figure out where
to put the speed selector.  I settled for a pull wire with a knob that
came out of the back of the phono.  Once you install the unit in the
cabinet, you will never see it.

The next step was installing a modern needle pickup, with a "flip" type
needle.  Next came the "balancing act" of getting the proper pressure
on the needle.

The M4 record changer is made for 10" or 12" records. It just so
happens that most 33 RPM records are 12" and the record changer works
perfectly with LP's!  I hooked the modified M4 to a amplifier, and
played a 33 RPM LP -- it worked perfectly.  I next played a 45 RPM,
then a 78; no problems.  The only negative thing is that the auto
changer will not work for 45's.

I fear that I have installed the wrong impedance pickup though;
I hooked the phono to the 48-1270, and I doesn't have enough volume.
I could use some advice in this area.  I know it's not the radio
amplifier, because the original phono, with it's pickup is plenty loud.

I am almost certain that this could be applied to other phonographs
of this era.

Andy Taylor

(Message sent Sun 8 Aug 1999, 19:59:06 GMT, from time zone GMT-0500.)

Key Words in Subject:  3-Speed, 78-RPM, Installing, Motor, Phonograph

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