[Phono-L] Amberola 30 erratic speed

[Andrew Baron]

Hi Ron ~

Is the slowing - resuming interval regular or random?  Random  
indicates a change that can't be predicted such as turns of the  
mainspring coil binding or slipping, and of course regular slowing -  
resuming (as you've already cited) indicates that it's related to the  
rotation of a particular gear or gears, arbor or bushing.

Another cause of unpredictable slowing can be mesh of two gears in and  
out of existing worn-tooth or worn-bushing areas.  In general, once  
there's sufficient loading by the power of the mainspring, the gear  
shafts move against one end plate or the other in a predictable way,  
so they don't swim in and out of existing worn areas, but it's  
possible to have TWO or more issues that interrelate, adding to the  
seeming randomness of the action and making it difficult to pinpoint  
the causes.  An example of this would be that the mainspring has some  
binding with resulting loss of power, which in turn causes one or more  
gear shafts to slide away from their normal lash-seated positions,  
which in turn causes the mesh or shaft to move in and out of a wear  
area at the whim of an unpredictable mainspring.

Yet another cause for the symptom you describe are gear sides (not the  
toothed edges) that rub, either against the motor frame or plate, or  
against another gear.  I had a Columbia BN once that had this problem  
due to a press-fit mainspring output gear that wasn't quite  
perpendicular to its shaft.  The side wall of this output gear would  
rub on the side of an adjoining gear in a relatively predictable way  
and was somewhat hard to notice.  Mainspring barrel lids that aren't  
fully seated can cause this as well, although these issues aren't as  
likely on a geared (no belt) Amberola motor.

The key to your search will be how predictable or not the slowing- 
speeding up routine is.

I hope this has given you some direction.  Let us know what you find.

Andy Baron
Santa Fe


On Sep 1, 2008, at 10:50 AM, Ron L'Herault wrote:

> OK, gang, it is time to tap into the lists' wisdom.  I'm working on an
> Amberola 30.  The hook came unsoldered and the reproducer needed a  
> rebuild.
> Those two easy repairs (the spring was in the case)completed, I  
> tested the
> phonograph and found that the speed is a bit erratic. It will sound  
> nice,
> then slow just a bit then return to speed for a while only to slow  
> again.
> The carriage moves easily and the horn bobbles and rotates as it  
> should.
> The governor is lubricated and the pad has been oiled.  There is no  
> evidence
> of crud or damage to the governor disk.  There were a few teeth on  
> the large
> hear that had a bit of damage but a bit of judicious filing has  
> cured the
> noise the damage created, and besides, the speed variation is more  
> random
> than the cycle of the gear noise.  I'm thinking that the mainspring  
> may need
> to be removed, cleaned and re-lubricated but I thought I might see  
> if there
> is anything else I missed before tearing it apart.
>
> Thanks,
>
> Ron L
>
>
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