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Kitcarlson

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 Motor Controllers:

Switches are used to open circuits to stop flow of current. A non pressed working controller, opens motor circuit. For safety, machine cord should be pulled from electrical outlets when not in use.

 Early 6 step wire wound resistors:
20190927_094950.jpg 
20190927_095102.jpg 
Six step controllers have six contacts selected by a sliding lever. The the first step (contact) is “off”, the last step is full “on”, between steps are four series resistor of about 35-45 Ohms each for 110V operation. The control with sliding contact is “off, 160, 120, 80, 40, on” assuming 40 Ohms each.  While it seems the steps might be course, they work well for speed regulation. Step technology is found in early singer BT7 foot controls, early knee operated bentwood controls, and portable Singer 101 portables. The resistors are hair diameter nichrome (nickel-chromium alloy) wire wound on a ceramic substrate. Contacts posts serve as junctions for joining of resistor segments. Sand and glaze mixture bonds wire to ceramic, and sometimes masks bottom terminals.

20191022_123445.jpg 20191022_153859.jpg 

The resistor above is defective.


Patent US1409950A,Application 1919-
7-18, Patent 1922-3-21

https://patentimages.storage.googleapis.com/65/d6/ea/f455a5b423ff2d/US1409950.pdf

Patent US1507734A, Application 1919-10-25 Patent 1924-9–9

https://patents.google.com/patent/US1507734?oq=patent:+us1507734

 Nichrome wire expands when heated by electrical flow, sand provides abrasive means, with use resistors may fail. With power off, resistor values can be measured between terminals.When resistors fail, the machine will still run, but without low speed regulation ability.

If controller passes Ohm test it is usable, but might need wiring replaced. To replace wiring, resistor needs to be removed, for access of terminals on bottom. The top steel control lever needs to be removed by loosening set screw on pin that holds it in place. The pin is removed, hold on to spring and roller that come out with lever. The plastic roller is an electrical insulator that isolates electric potential of selector blade from lever. Three screws with fiber washers top and bottom, mount resistor to housing. If washers stick to resistor or housing, leave them stuck, it helps in reassembly. Reassembly requires location adjustment of resistor in housing. It is very important that rest location, is on first terminal “off”, and wiper does not contact second terminal or housing (+1/8” gap. When sliding top lever to full “on” at limit slot, selector lever should be at last terminal, and not extend to contact housing (+1/8” gap). There is slop in the mounting locations, accommodating small position changes. Adjustment may require a bit of trial, the lever must be installed to test (without return spring), but conflicts some with mount screw access. Do not over tighten screws or leave out fiber washers, resistor might stress fracture. When assembly work is complete, verify controller electrical terminals are isolated from housing.

Early step controls were used about a decade, then replaced with carbon disk piles.  Nichrome replacement wire is readily available. Removing old glaze, rewinding, re glazing, and expecting long term fix is questionable. I have tried simple fix, re-flow of solder connections, without resistance change.

Early machines are easily upgraded with used of later bentwood style controller, or addition of later foot control, enabling controller section of bentwood to be used for accessories. There were a few variations in bentwood internal controllers over several decades of production. The changes involved controller body, controller, terminals, wiring details, cover plates, and knee control bars.

 Carbon Pile Controllers:

The Featherweight shop has an interesting information on single button controllers here:

https://singer-featherweight.com/blogs/schoolhouse/original-featherweight-foot-controllers

Single button, Bakelite case. Often need foot bumpers, cleaned inside of lint, wiring replacements. Less often mechanical adjustments.

Carbon pile controllers can be adjusted if stacks of carbon washers are complete and unbroken. There is an off adjustment, where stack has zero pressure, with no conductivity. Very important! If stack is conducting and left plugged in, long time undetected, it may over heat, motor too! Other adjustment is high end bypass, it provides full on, zero resistance. These adjustments are checked with an Ohm meter at two terminals, that connect to cable, without AC on of course. The Featherweight shop has a nice videos on adjustments.



20190927_095139.jpgCarbon pile resistors were also incorporated in bentwood bases, and some Singer cabinets with knee bar operation.

Patent US1792818A Application 1927-12-16 Patent 1931-2-17

https://patents.google.com/patent/US1792818A/en?oq=patent:+us1792818A 


Electronic Controllers:

Electronic controls use electronic switches called triacs to switch selected portions of power signals, regulating motor speed. Triacs are used in light dimmers. The selected power portion, is what your foot desires by depressing pedal. The unused portion is not taken from power line.  

My wife likes electronic controls. They are light weight, easy to press, and smooth linear operation. A control without cables under $20 from Sew Classic. Ngosew on ebay has electronic controls with cables for $23.50. Electronic controls are energy efficient and run cool. Additional information is in a post about RPM and power measurements.

https://www.victoriansweatshop.com/post/easy-motor-rpm-and-power-measurements-10388153?pid=1310367425

20190927_134741.jpg 

 



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Dave in middle TN
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Mavis

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Reply with quote  #2 
Thank you for posting this.  So much I have to learn and start doing!
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Cari-in-Oly

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Reply with quote  #3 
About the electronic controllers - Buyer beware when you go the cheapest route. I've seen several people in the last couple of years complaining that their el cheapo electronic controllers died within a couple of months. This is mostly people who bought cheap on Ebay. Just sayin, cheap isn't cost effective when you have to rinse and repeat.............

Cari

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Chaly

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Reply with quote  #4 
I've also heard with the electronic controllers it is important to have surge protection - maybe this is the reason for the failures?
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Kitcarlson

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Reply with quote  #5 
I have purchased about a dozen, some for friends, no failures. My wife really likes them. She started with one, and moved it around between machines and homes. I bought more for her portable machines, and her numerous sewing stations. She loves sewing, and does much of it. About 3 year history on electronic. She uses a switched surge protected outlet strip, on most used station. It is a time saver to flip instead of pulling a cord.

A surge protector has a device called MOV, it clamps transient over voltage in line power. Transients happen with lightning strikes and power system disturbance, example car hitting pole. The surge protector should help protect electronic control.

The wire-in controls come with wire nuts. I use crimp splices instead. Perhaps some failures are connection related.

I am curious what type of failure? Semiconductor (triac) used in controls typically fail shorted, that would make controls be full on. A control not running machine, may indicate connection problem, or mechanical linkage issue.

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Dave in middle TN
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ke6cvh

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Reply with quote  #6 
I have experienced failed MOV's, metal oxide varistors, before repairing TV's.  An MOV is like a car battery in that it is designed for short times of protection but each time it clamps the life of it goes down.  The higher the current it clamps at the lower the life expectancy just like with car batteries that are not deep cycle if you cycle them deep the life of the battery drops dramatically.  When I fixed TV's with this problem I just cut it out and the TV stopped blowing fuses.  Took me seconds to diagnose and fix.  At one communications station I was working the local national tech's had made diy surge protectors by taking parallel solid copper wire then soldering about 1 dozen of them in parallel.  It worked and was pretty smart inside a generic enclosure.    I have never experienced an electronic controller fail on my domestics even once.  One can buy the MOV's out of places like digi-key and Mouser fairly low cost.  Higher quality surge protectors have more to them than just a clamping MOV.  If I did have an electronic controller fail I'd likely just buy a new one instead of fixing it with a parted out light dimmer circuit unless I was trying to keep the originality of the pedal then that is what I'd do.  Best regards, Mike
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Kitcarlson

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Reply with quote  #7 
While out working clearing fence of honeysuckle i thought more about controller failures. I have had failures on power tools, a dremel tool, and heavy duty drill. Both devices had motor rotor issues, with commutator erosion. Rotor winding shorts create high transient currents with related voltage transients. Defective motor, failed built-in controls.

It is highly possible a carbon pile control will survive, with defective sewing motor. Not saying it is always a motor.

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ke6cvh

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Reply with quote  #8 
I agree and would look at the motor and/or electrical system of the sewing machine motor before suspecting the power from the grid as being the source of failure. TRIAC circuits have been used in light dimmers until they began to be replaced by PWM/digital dimmer for L.E.D. circuits.  I've never seen a TRIAC based dimmer fail either.  I used to use them for a DIY dimmer on my soldering iron for heat control...never had a problem

  One thing to be aware of for sure is that allot of these electronic variable foot controls on Amazon get a bad rap because they do not match them to the tool being used ending up with a transition from nothing to full speed too quickly.  I'd recommend sticking to the ones made for sewing machines which likely are all coming out of the same factory or couple of factories in China.


Best regards, Mike

Edited to add:  An MOV is not going to limit input current to the pedal if there was transient loads peaking above the rating of the TRIAC circuit.  Really old school TV protection circuits on some of the circuit boards would use 2ohm resistors taught to me by a Navy Chief that used to get his drinking money from fixing TV's....needless to say he was quite talented at fixing TV's.  If I had problems with transients I'd be doing exactly that placing a 2 ohm power resistor in series with the pedal to limit the surges.
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ke6cvh

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Reply with quote  #9 
Hello group,  This 10w wire wound 2ohm resistor would be a good candidate on Amazon to go in series with the foot controller.  To get to 10w one would need 5 amps continuous current in the circuit which is going to be much higher than the rating of the motor.  Let's say it is a 1.3 amp Kenmore motor.  Then one would be dissipating 2.6 watts power in the resistor and the rest of the power would be in the motor (143 watts in a 110v ac circuit assuming there is no PFC power factors involved in the circuit).  It has little holes so it can be mounted to something.  Fairly certain that it would limit the transient shorts in the rotor.  It is even advertised on Amazon for L.E.D. light dimmer circuits.  If I convert a machine to electronic foot pedal I may just do this mod myself.....

Best regards, Mike


https://www.amazon.com/LM-YN-Wirewound-Electronic-Industrial/dp/B077BLLSJQ/ref=sr_1_5?keywords=2+ohm+power+resistor&qid=1578421540&sr=8-5
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Kitcarlson

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Reply with quote  #10 
There is several Ohms of series in a sewing machine motor due to brushes, rotor and stator windings, adding a couple Ohms outside may, not be appropriate due to safety issues. The triacs may have a voltage rating of 400V, an MOV will help, and motor resistance and inductance will limit current. A short in motor wiring, will most likely kill a controller.
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Reply with quote  #11 
Hi Dave, 

  Yes there may be several ohms in a working motor.  What we are talking about is a faulted motor that is having transient shorts as the rotor turns.  The MOV would never see a rise in current in the circuit the way they install them as they are wired in parallel to the input of the circuit.

  What would happen in a short is that the small value power resistor would heat up internally and open.  These power resistors have classes normally seen by the part number and in this case is resistive wire made into a coil usually NiChrome wire of the correct mix.  Resistor is encased in aluminum with heat sinks so it would never have time enough to overly heat the aluminum casing as the wire would open up before that occured.  The circuit would have a fuse in it before the MOV.  In reality one would need to install an MOV after the input fuse to the circuit.  The resistor would act as a slow blow with the fuse as a fast blow and the resistor would also act as a current limiting device for transient high current spikes.  I would add a 5 amp quick blow or possibly a little less but not the same as the motor itself.  

  If the circuit was fused before the pedal/circuit itself and the resistor in circuit between the pedal and the input to the motor, in practicality, there would not be an issue of any of the house wiring being at risk in a 15 amp/110v circuit.   The fuse would protect the house wiring as intended in a circuit like this.  Link for varistor page below.  One can use a higher clamping than 120v but the MOV will never become active until that is reached.

  Some high end surge protectors are made properly and have more than 1 or more MOV's in parallel with the input.  They will have a coil as part of the circuit.  What happens with the coil can be flyback effect.  This is how anode voltages on older color TV CRT's worked as they would use the flyback transformer to generate voltages over 30kv with color and 20kv with black and white CRT's.  Fly back effect has to be taken into account in these types of protection circuits.  The power resistor is a coil as well but at 60hz it will have negligible fly back effect.  In a transient situation it would also be the same for the coil in the wire wound power resistor (this is assuming the coil is not wound with contra windings to counter the fly back effect which is likely the case).    

  The MOV acts as a passive device until the voltage seen across it's terminals meets the design voltage and then becomes a short across the terminals clamping the voltage to it's designed value as long as the MOV has not failed yet.  Typically MOV's like this are rated at 120v.  In theory if the voltage was not excessive but still within it's clamping range the only thing that would happen would be the input voltage would be regulated by the clamping action of the MOV and the motor/foot pedal circuit would continue to operate as if nothing occurred.  In reality the clamping action generates heat and the larger and longer the surge it is clamping is then the greater the power that must be dissipated by the MOV causing two things.  One is degradation of the MOV in future cycles of clamping (like a car battery that has been discharged overly) and two if the heat built up is large enough the MOV shorts internally as it's failure mode.  I've seen lightning strikes that have blown holes in MOV's before and just cut them out with a pair of wire cutters with the TV perfectly fine after the fuse was replaced (fuse and MOV acting together to protect the TV).   Also, if not so drastic the MOV can open up and no longer clamp if it has seen too many clamping cycles but that would occur where there is not as much heat build up with lesser clamping cycles repeatedly occurring.  This is where I have seen multiple MOV's in parallel to limit the power dissipation and also the amount of surge seen by each MOV so they work together synergistically to get a longer lifespan protection device. There are graphs made by the manufacture of these MOV's that show this degradation vs clamping voltage and time with a rise in degradation that occurs with time and clamping voltage (regulated voltage of the device essentially).  In a way the MOV can be seen as a zener diode in a regulating circuit but in practice it has different properties than the zener just similar (zener diodes are used in DC regulation as they are diodes that are doped to act in this manner so will conduct in one direction but act as a regulator when inserted backwards for the PN junction in the avalanche region of operation).  

  So the way I see it is the entire circuit actually becomes safer through the installation of a fusible resistor between TRIAC circuit and motor along with an actual fuse at input before the pedal circuit.  If it was 220v I would put two of them in parallel (Amazon is selling them in pairs).  I've seen discussions where folks talk about modifications to electrical stuff and the obvious is it will not be UL listed 😉  For my own personal use I would not hesitate to have added protection in a circuit but it might be beyond some skill and understanding levels.  It is difficult to determine if 2 ohms is a good value or not but less ohms mean less power in the circuit being consumed by the resistor.  Manufacturers must balance profit along with cost when it comes to protection.  A good example is the protection devices I have on each of the input of my breaker boxes for each string of solar panels.  I purchased the best that was tested under calibrated/certified test equipment.  There is a video where they compare the performance of the Midnight Solar brand US made protection to the other brand which is lower cost and very popular.  Amazingly the other brand uses sand (no joke) as part of the protection circuit.  In the video it is shown that this device essentially does nothing.  This device also uses multiple MOV's in parallel as only part of the circuit.  It also has a circuit that has an L.E.D. for normal operation and one that shows a faulted input scenario.  I'd rather spend the extra money than have a roof catch on fire (in my case it is a metal roof so very unlikely but it has occurred elsewhere causing the requirements of the circuits to change due to danger of wood roofs and solar arrays).  

  The problem with the motor is not going to go away if it has a faulted rotor that is for certain.  In best case scenario one would start blowing fuses and then need to investigate.  If lucky maybe it is just worn carbon brushes causing transient shorts and the entire circuit would be restorable with a new fuse, new set of carbon brushes, and a good/proper cleaning of motor.  In the case of a worn rotor because it was run too long with worn brushes or just reached it's service life end then in best case scenario it would be a replacement motor and fuse but not the pedal or resistor.  

  If it was a 2 ohm and motor draw was 1.3 amps under normal operation at full speed then at full motor speed the resistor is dissipating 2.6 watts or roughly 1/4 of it's power rating.  At 1.3 amps and 110v (without any power factor so assuming a resistive circuit) it would be 143 watts for the motor in the circuit.  This means that 1.8 percent of the power in the circuit would be dissipated by the resistor or an added loss in efficiency that is negligible.  At lower motor speeds than full with no transient shorts the power dissipated by the resistor is less.  I'm not inventing the 2 ohm fusible resistor.  It is very old school and been around for a long time but likely fell out of favor decades ago.  It seems ideal in this case but again would need to be matched to the circuit which it seems it may be.

  Without the proper protection circuit installed in the motor/pedal circuit then one may just have to count on replacing motor and pedal as a pair.  A surge protection strip is not going to do much unless it is designed/rated for the current of the motor and not for 15 amps.  It will protect from large transient input spikes of voltage but this is not the failure mode we are discussing so not part of the solution.

Best regards,
Mike
https://www.littelfuse.com/products/varistors.aspx

  edited to add that sometimes folks need to be a little outside the box to fix problems.  I have a diy whole house water sanitation system that uses dual UVC lights in series (and another under the sink in kitchen where it becomes three in series).  The circuit is very sensitive for the ballast with an alarm.  I would get no alarm off the grid but when using my US designed/manufactured "pure sine wave" inverters I'd get alarms constantly due to RF hash on the inverters sine wave.  I bought two 400 watt step down transformers with fuses as part of the case.  I wired them back to back so went from 230 to 115 back to 230.  It puts hospital single stage isolation transformers to shame.  Likely in an alarmed state the UVC was not operating at all but the documentation did not cover anything like that.
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Kitcarlson

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Reply with quote  #12 
Mike,

We differ greatly in our understanding and use of electrical concepts.

For safety sake, I do not recommend modification as suggested in post #9.

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ke6cvh

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Reply with quote  #13 
Hi Dave,

  Here is a web site for fusible resistors and their comment regarding them.  It specifically states "protection from abrupt transients and meets safety requirements".  Sorry about the highlighted large paste it came out that way not on purpose 😉  Also, link below.  I agree most on this forum do not have the skills for this but again I wouldn't hesitate in a second to do it here but I've got over 33 years in the electronics field before retirement so it is different here.  I thought it was a decades old technology but it appears it's still used for this purpose.  Best regards, Mike  :

Fusible Through-Hole Resistors

Designed to protect circuit from abrupt transients and meet safety requirements

Image of Yageo's Fusible Through-Hole ResistorsYageo offers complete range of fusible resistors which operate both as a normal resistor and as a fuse. The resistors are designed to protect circuit from abrupt transients and meet safety requirements  https://www.littelfuse.com/products/varistors.aspx

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Kitcarlson

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Reply with quote  #14 
Here are pictures of product labels on well used controllers.  The ngosew is 3 years old, it has been used on many different machines.  Both have sewn several quilts and other sewing projects. My wife says they work like new and there is no difference in operation.
20200108_065445.jpg 

20200108_073659.jpg 
20200108_081057.jpg 
The ngosew controller is lower profile, and refined in looks than one at bottom of post 1, that goes with top label.



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Dave in middle TN
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ke6cvh

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Reply with quote  #15 
Hi Dave,  I've bought some folders and such from NGO sew..good sellers.  They were going to get me a custom made folder out of Vietnam for one of our waist band machines Union Special 51800 with differential puller but I got distracted and didn't yet follow through with it.  That product label says allot with 1.2 amps rating.  They have in the radio world what is called continuous duty and ICS which stands for intermittent continuous duty (confusing I know but that basically translates to you can do it but not continuous til the cows come home as you'll burn it up before they show).  I just ordered a motor out of China I want to test that is 250 watt rating and 0.9 amp at 220v.  Using ohms law that means it is a 225 watt rated motor which makes me think they are rating it off of peak current or taking also into account some really bad efficiency with the power factor thrown in.  I know that Sail Rite rates their motors at 50 percent efficiency and have to wonder if this improved motor is what they are using.  At 110v that would be 1.8 amps (I haven't checked if they have a 110v version of this 250 watt motor but have seen plenty of 1.5 amp motors on eBay) so it is way beyond the rating of the foot pedal.  An older Kenmore at 1.0 amps and much better a Singer at less would be more like it.  Maybe this is where the problem is arising?  I've also seen the motor and pedal sold as a matched pair but that will surely be carbon pile and warm feet.  Best regards, Mike
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ke6cvh

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Reply with quote  #16 
Here is a matched pair of a 150w motor/1.5 amp rating with electronic controller.  If I was to go the 150w/electronic pedal route I'd likely do that.  We're 230 here. 
https://www.ebay.com/itm/Sewing-Machine-Motor-Electronic-Pedal-Set-1-5-amp-Singer-15-66-99-99K-27-28/201534732956?hash=item2eec67fa9c:g😋dIAAOSwZ8ZW2Sgm

  Here is the 220w/0.9a motor at 12,500 rpm I bought:  https://www.ebay.com/itm/250W-220v-household-sewing-machine-motor-12500-r-min-with-foot-pedal-controller/263962346579?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

  And then there is this 220w/0.9a motor at 10k rpm for less than half the price but they only rate it at 180 watts even thought the voltage and current ratings are the same (with different power ratings).  This stuff cracks me up on their ratings being all over the road:  https://www.ebay.com/itm/220V-180W-0-9A-Quality-Household-Sewing-Machine-Motor-10000Rpm-for-Househol-Z8W6/254419363962?epid=14034385326&hash=item3b3c93687a:g:Y6EAAOSwD1Fdyv5w

  And with all that said here is my favorite motor....we have one on a White Rotary....I bet Dave's electronic foot controller would sing with this motor nicely if the original one was beyond service:   [cool][biggrin]  https://www.ebay.com/itm/HAMILTON-BEACH-SEW-E-Z-SEWING-MACHINE-MOTOR-NO-2T-256448/324031545277?hash=item4b71c8ffbd:g:seMAAOSwPn1eD6Lz  

 
 Edited to add this motor that claims greater than 70 percent efficiency getting 250w out of a 1.5 amp motor kit includes pedal.  This is a 75 dollar combination.  Says it runs cooler.  Kind of looks like the motor I bought out of China claiming 250 watts.  Would be interesting to see how they claim their upgrade in efficiency if it is permanent magnet or what....will look into it for my own use: https://www.ebay.com/itm/Sewing-Machine-DC-Motor-Upgraded-Pedal-1-5-AMP-Singer-Brother-FULL-250-WATTS/201597571607?epid=926479905&hash=item2ef026d217:g:fVUAAOSwIS5c2Fdy#rwid
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