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Old 3rd Jul 2022, 4:31 pm   #1
EF80TVVALVE's Avatar
Join Date: Feb 2010
Location: Leicester, UK.
Posts: 1,195
Default Ampro New Educational - motor woes, issues and solutions

Hi all

Some may remember we previously discussed the Ampro New Educational amplifier some time ago. At the time I was also having a problem with the motor, on the odd occasion it would drop in speed, almost stalling. A flick of the on/off switch usually had it back working okay. At the time giving a visual inspection I found there was a Hunts Mouldseal capacitor inside the motor itself and thought this to be the likely cause.

Fast forward a long time until today and I decided with a spare afternoon I should tackle this motor and get that capacitor replaced. After much frustration the motor was free, although still wired in to the projector. It's here that you have two options, either conduct what is equal to keyhole surgery on the motor to remove and replace the original capacitor or unsolder all motor wires and completely remove and fully dismantle the motor to gain good access to the motor.

Due to the design of the motor its impossible to lift the back housing clear of the spindle due to the internal wiring. To completely remove this the windings must also be loosened off and removed along with it. This is due to two carbon brushes that sit on the end of the motor body which make contact with a rotary centrifugal contact breaker for the speed regulator.

This speed regulator is where I found my next problem, the points have a lot of pitting so I had to remove and file back as much as I could, this still leaves a fair amount of pitting on the points but after several attempts of cleaning, refitting checking, removing, adjusting etc I now have the motor working relatively well, it still however runs a little uneven at times but no severe speed drop or stalling.

I'm now at the point where I know that any more rough running is due to this speed regulator which is somewhat unfortunate. I have tried scouring the Internet for ampro spares in hopes that spare breaker points are available, but it seems like none can be found.

The next thing is to see if this type of centrifugal breaker regulator can be serviced, ideally if anyone knows the actual name for this sort of speed control then that may lead me to the right path, alternatively I'll have to see what I can do with some breaker points for an old car and see if they can provide spares suitable to repair these.

Aplogies for the lack of photos, when I have the cover off again I'll add some to the post!
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