On 8/22/2020 12:04 AM, wrote:
I have an old Singer sewing machine. It is a model 221, AKA a
Featherweight. I got the thing at a garage sale for 5 or 10 bucks and
everything was there but the foot pedal motor control.
So I bought a modern PWM style control instead of an old carbon
disc style one because it was supposed to be better. At least I think
the new one is PWM. It is very light and doesn't get hot after lots of
use.
I think it may be under performing though because the little
machine seems to run too slow. I did go through the machine, cleaning
and adjusting it. It was dirty inside, had old congealed lubricants
clogging and sticking stuff up. Things were also really out of
adjustment so it would not have been able to sew even if it was
turning freely.
The machine now turns quite freely. It is oiled with the proper oil
and the motor, which I also cleaned and lubricated, is lubricated with
the proper grease.
So after all that the machine still runs too slowly. At least in my
opinion. The motor just doesn't seem to have much oomph and I'm
wondering if maybe the foot pedal control is not delivering enough
current and/or voltage. Since the control is PWM output would an
analog meter like my Simpson 260 be a good tool to measure the current
and voltage?
Or maybe someone here knows already about these machines and the
foot controls and can tell me what to expect from a properly
operating control. And the best way to check it.
Thanks,
Eric

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I've seen designs - but not the actual product - of cheap motor
controls that can provide only half the power at full throttle.
This is because the phase-controlled device is an SCR without any
pre-rectification and conduct for only half of each AC cycle..
Maybe you have one of those.