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Jerry Peters

wrote:
On Mar 7, 3:54 am, Matti Adolfsen
wrote:
wrote:
The machine will start very slow. There is only one motor on this
machine. Initially there is very little torque and low speed. After
about 30 seconds or so the speed and torque increase however it never
reaches full speed. The tape runs slow. I have lubricated it and there
doesn't seem to be excessive play in the bearings nor is it binding.
Does anyone know what would cause an AC motor such as this to exhibit
these symptoms? This motor was used in an old Ampex audio tape
recorder manufactured in the late 1950's. I'm in desperate need of a
replacement or repair information for this motor. The label reads:
Howard Industries Inc.
Festus Missouri
Loyd scruggs Div.
115V 60cy.
Model: 28125-2903 .7A 55W Code 1061

is this a synchronous motor with capacitor? at 60 Hz, a 4 pole motor
gives you 1800 RPM, 6 pole motor gives 1200. A common failure is a blown
capacitor, resulting weak torque and starting problems.

Sometimes they used capacitors with PCB. be careful, this is poisonous.

Hope this helps
Matti Adolfsen
Kemi
Finland

I disassembled the motor cleaned it and lubricated it with ATF. It
appears to be in very good condition. There is no end play in the
bushings and very little apparent wear. It starts better now and comes
right up to full speed, however the speed is 1720RPM either loaded or
running free. Same as before the cleaning. There seems to be four
poles which would suggest 1800RPM as you mentioned. Is it
theoretically possible for a four pole motor to operate at 1720RPM?
Varying the line voltage around 120V has very little effect on speed
so it appears that it is running synchronously. There is no capacitor
externally or internally. I just can't imagine what could have
possibly failed (if something did), to cause this. Lenny

If it's not really a synchronous motor, it's normal for it to run
slightly slower than 1800 rpm. How much slower depends upon the actual
motor design.

Jerry