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Old December 27th 20, 08:04 AM posted to sci.electronics.repair
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Default Rectifier added after factory assembly? Was Help please with PWMsewing machine pedal

On Wednesday, September 9, 2020 at 4:05:35 AM UTC-4, Cydrome Leader wrote:
wrote:

Did you mess up the timing of the motor by chance? The angle of the
brushes makes a huge difference.


maybe? How's the motor run with no speed controller?



The brushes are sleeved and fit in only one way. About the only other
'unusual' possibility is that Eric has a Euro version - which has flat
paper caps in the motor. They should be REMOVED and NOT REPLACED!

Peter WIeck
Melrose Park, PA

It's only somewhat related to this, but I have a precision drill press
with a real goofy looking manufacturer supplied speed controller. I called
them up about something unrelated and and issue of weird bursts in speed
came up. You'd have no load on the motor and it would randomly start to
race.

The suggested fix was to open the speed controller and cut out a bridge
rectifier that turned the AC output of the triac speed controller and just
let the motor get AC.


So, the rectifier no longer turned AC output of the controller to DC? So, the controller wasn't used after that?

It worked fine after that. I'm not sure why they added a bridge recitfier
in the first place, or why removing it made a difference but it did.


Didn't they need DC to the controller's resistor circuit?

The
motor is pretty similar is size to a sewing machine motor, and the
standard universal motor type deal. The whole controller is cobbled
together looking so I can't even tell if they added the rectifier or the
OEM did.


Oh, the rectifier was added after the original sale.

I'm sort of tempted to try the drill press with a properly designed
industrial speed controller (Dart Controls), with and without the bridge
rectifier to see how it behaves.


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Old January 11th 21, 09:39 AM posted to sci.electronics.repair
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First recorded activity by DIYBanter: Jul 2006
Posts: 1,872
Default Rectifier added after factory assembly? Was Help please with PWM sewing machine pedal

bruce bowser wrote:
On Wednesday, September 9, 2020 at 4:05:35 AM UTC-4, Cydrome Leader wrote:
wrote:

Did you mess up the timing of the motor by chance? The angle of the
brushes makes a huge difference.

maybe? How's the motor run with no speed controller?


The brushes are sleeved and fit in only one way. About the only other
'unusual' possibility is that Eric has a Euro version - which has flat
paper caps in the motor. They should be REMOVED and NOT REPLACED!

Peter WIeck
Melrose Park, PA

It's only somewhat related to this, but I have a precision drill press
with a real goofy looking manufacturer supplied speed controller. I called
them up about something unrelated and and issue of weird bursts in speed
came up. You'd have no load on the motor and it would randomly start to
race.

The suggested fix was to open the speed controller and cut out a bridge
rectifier that turned the AC output of the triac speed controller and just
let the motor get AC.


So, the rectifier no longer turned AC output of the controller to DC?
So, the controller wasn't used after that?


Correct. The chopped up AC was no longer full wave rectified into choppy
DC. I never looked at the waveforms, but they were probably awful.

It worked fine after that. I'm not sure why they added a bridge recitfier
in the first place, or why removing it made a difference but it did.


Didn't they need DC to the controller's resistor circuit?


There was no feedback from the rectified output. I keep thinking it was a
wall mounted light dimmer or something cheap like that inside the box, but
with an electronics-looking knob.

The
motor is pretty similar is size to a sewing machine motor, and the
standard universal motor type deal. The whole controller is cobbled
together looking so I can't even tell if they added the rectifier or the
OEM did.


Oh, the rectifier was added after the original sale.


It was added at the factory. My only modification was to remove it, as the
support people suggested.

I'm sort of tempted to try the drill press with a properly designed
industrial speed controller (Dart Controls), with and without the bridge
rectifier to see how it behaves.


I haven't run this test yet, but will soon.


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