: V-M speed too slow  ( 634 )

Motorola Minion

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V-M speed too slow
« : January 05, 2020, 07:58:49 PM »
I have about four V-M 1200 series changers and all of them consistently run a bit slow.
This is true of 33, 45 and 78 speeds, all a bit slow according to the strobe disc. Its not the idlers, they were swapped with rebuilt ones.

The line voltage is not the problem, it is over 120. The line frequency is 60 HZ according to my Fluke DMM, so it's not that. I have a very low-hours motor that I will try in one of the slow ones that is a repair job,. That one cannot go back to the customer like that.

What could be the issue is a worn capstan (but on all 3 speeds ?) or inner surface of the platter, which is often painted to match the surrounding metal finish.

Has anyone encountered this issue and what made it better?
Tubes - Magical - Tubes

Dave

Ken Doyle

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Re: V-M speed too slow
« #1 : January 06, 2020, 10:18:46 AM »
Does the motor spin for a while when you kill the power?  The motor has to spin very freely and should take it's time coasting down. 

If not, when re-assembling the motor, before you tighten the screws, tap the motor shaft with a screwdriver handle a few times.  This will properly line up the bearings.

Motorola Minion

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Re: V-M speed too slow
« #2 : January 07, 2020, 08:29:16 AM »
Motor testing should be part of the routine, I know at least one of those Alliance-type shaded-pole motors has a "spun" bearing. the shaft is not smooth.

The fact these use pillow-bearings underscores the need to align these during reassembly :-[
Tubes - Magical - Tubes

Dave

Ken Doyle

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Re: V-M speed too slow
« #3 : January 07, 2020, 05:40:18 PM »
The fact these use pillow-bearings underscores the need to align these during reassembly :-[



"Pillow bearings", I never knew that's what they're called.  You learn something every day. Thanks for the info.

Motorola Minion

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Re: V-M speed too slow
« #4 : February 04, 2020, 03:38:05 PM »
I have about three of these players that I have successfully increased the speed so it is slightly fast now on all three.

Prior to soaking bearings 24 hours in mineral spirits, draining dirt and old oil out, then filling with supco turbine oil, they were all slightly below speed.

According to the strobe disc, the rectangles shall remain stationary if dead-on 33.33, 45 or 78 rpm. Remember 33+45=78 :-X

Before oil changes, a whole rectangle slipped to right in one second's time.

After oil changes, about 1/3 of a rectangle advanced to left in one second's time.

I assume at some point, it will slow down again but this appears to be the great compromise of not having a pitch adjustment like my Technics SL-B1

I know there is some app for measuring RPM with a cellphone but I'm satisfied. Now to work on my Magnavox and Dual 4-pole motors....
Tubes - Magical - Tubes

Dave

Motorola Minion

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Re: V-M speed too slow
« #5 : February 26, 2020, 04:04:07 PM »
RCA motors look the same as V-M because they were all made by Alliance, the original Tenna-rotor
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Dave