Broken Electric Motor? HOW TO Test If A Motor Armature With Commutator Is Damaged

When an electric motor is broken, one suspect is the armature with commutator of the motor. In this video, we show different tests (180 degrees test, bar-to-bar test, continuity "bar to stack" test) that can be completed to determine whether or not the problem with the motor is caused by the armature with commutator being damaged or having failed. Note that those tests apply to DC motors and universal motors that use a motor armature with commutator.
In my case, the armature, coming from an old circular saw, was found to be faulty. Was it a surprise? No. Other signs of the armature having failed included:
1) Motor not reaching full speed when using the circular saw
2) Smoke coming from the armature when using the circular saw
3) Motor not spinning at all when placing the motor brushes on A specific commutator bar (the one where the resistance drop in test #2 was observed)
4) Irregular film left by the brushes on the commutator bars
Cause of the motor failure? Short in the armature windings.
But ultimately because I'm an ass!
Short in the armature windings was because the coils got too warm
The coils got too warm because the tool had to draw too much power
The tool drew too much power because I pushed an old saw (with possibly degraded winding insulation) into cutting off wood that was too thick, too fast and on a super-hot summer day, so ultimately, the tool failed because I'm an ass.
► To check the motor field coil / stator, see:
• HOW TO Test If The Mot...
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For this project this means, make sure not to eletrocute yourself, even if you find it fancy
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[@jorma4382]

Straight to the problem, no bullshitting, watching the video solves all your problems. Thanks! ❤

[@TheLabOtomy]

Thanks for the feedback

[@Markus.Cantor]

What an excellent find! I appreciate the pacing and just the right amount of information to get you going without being overwhelming. Extra props for being so active in your comments. I'm looking forward to checking out all you have to offer. Thank you, good job and keep up the good work!

[@TheLabOtomy]

Thanks for the kind words, hope you will find something of interest in the channel

[@CJWarlock]

Best presentation of this kind I've seen on YT. Congrats! :)

[@TheLabOtomy]

Thanks for the positivity!

[@astina6]

Love these videos short and to the point...kudos !!

[@TheLabOtomy]

Nice!

[@jet-z2r]

I was out driving my 1944 GPW ford jeep. I noticed the amp meter was not working, reading zero. I decided to head home as i became worried. The amp meter needle then moved into the negative side of the guage which indicaded the battery was been drained on energy. After a while the needle moved to show a positive charge. i thought ok, all good, jeep has fixed itself. 😅👌🏻👍🏻. As i continued along home, suddenly the amp meter went totally crazy. The needle was flicking from side to side, the higher i reved the engine, the more violently the amp meter needle flicked from side to side. 🤤😓😭😭. I made it home ok. My jeep has a 12 volt system. New external voltage regulator & battery installed 3 months ago. I didn't know what to do or where to start. I found your video , thank God. Removed the generator/stripped down. Generator internals were filthy/full of dried dirt/dust as if it was dropped in mud for 6 months, then installed in the jeep. Probably dirt from world war 2, 😅🤣. Completely cleaned the internals with contact cleaner aresol, housing/armature/commutator. Surprisingly the 2 brushes had probably 60 to 70 % left.. Cleaned commutator bars where the brushes make contact with 800 fine grit paper. Commutator bars came up like new. Filed the brush surface that contacts the commutator bars with a file, so it was flat for better surface contact with the commutator bars. Done 3 tests on the armature as per your instructions. 2 ohms & 1 continuity tests. Armature passed the tests with flying colours. I assembled generator/ installed in jeep, left the fan belt off the generator. To test the generator, i connected a wire between field terminal & armature/dynamo terminals on the generator . I then ran a 2nd wire from the positive side of the battery to the wire that connected both terminals on the generator. The negative lead must be connected to the battery. The pulley spun on it's own indicating it was working properly. Connected up wires, started jeep engine. Reved the engine to approx 700 to 900 RPM, amp meter needle moved across to the positive charge on the amp meter. Tested battery charge rate was 14.2 volts at approx 700 to 900 RPM. All the problems were caused by a gut full of dirt in the genny, 😅🤣😂 Thankyou for sharing your information, really got me out of trouble. 😂🤣😅👌🏻👍🏻👏🏻👏🏻👏🏻 Cheers from 🇦🇺

[@TheLabOtomy]

Thanks for sharing. happy to read it has been helpful

[@johnfreeman6352]

Thank you very much for the video It is a very good demonstration. 1) Could you please confirm though an easy way to measure correctly /accurately 180 degrees on the part indicated. 2) In the 2nd test are you checking comparing the 1st with 2nd (and) the 2nd with the 3rd and so on OR the 1st with the 2nd (and) the 3rd with the 4th and so on. I look forward to your reply From a Learner Thanks

[@TheLabOtomy]

Hi John, 1) for the 180 test, value itself is not important, consistency is. I usually mark on the commutator the start and 180 position and check every time I have landed on the right slot. 2) For the bar to bar test, go 1 to 2, 2 to 3, 3 to 4, etc The idea is to check if their is unbalancing across the wiring, which indicates an issue impacting the engine to properly turn. 180 test or bar to bar is simply to make sure a similar portion of the wiring is checked every time. Hope that clarifies.

[@powertoolsrepair]

very informative video and very good edited. Thank you

[@TheLabOtomy]

Thanks

[@llamadeudun8291]

Gracias por brindar tus conocimiento! estoy reparando un cepillo eléctrico makita y todas las pruebas tengo luz verde, pero aun así chispea mucho el inducido al prender la maquina, lo que noto es una decoloración en algunas delgas y no hay ninguna delga levantada para presentar esta chispa, mi conclusión es que hay algún corto interno entre las delga del inducido pero no en el cableado de las bobinas.,

[@angelnoheart1167]

..my utmost thank you to you.. I have a gbh 4-32 that has been broken for a long time and I was thinking of throwing it away but after watching this video and a few other related videos on your channel, the machine is now working.. i subscribe..

[@TheLabOtomy]

Nice Angelnoheart, always good to hear about people fixing their stuff!

[@gnorrie3501]

Great video I have a bunch of Tecumseh Snow King starters to check.

[@TheLabOtomy]

Good luck

[@villacoya]

excellent video

[@TheLabOtomy]

Glad you liked it!

[@colin5064]

First class instruction excellent video

[@TheLabOtomy]

Thanks!

[@farhadtorkaman6553]

Perfect 👌👍Thank you 🙏🌹

[@TheLabOtomy]

👍🌹

[@dawnninorvince2127]

One of the Best Tutorial DIY because he was Clear, non monotone, and easy to understand,and to the point without any bull. I would like to know: if I purchase a motor followed hooked up wiring as per direction from rear ran fine for about one 1 min then slowed down , this is to a compressor that has ben running for 16 years so power to the power switch is more than fine. Help me. Ps this is the second motor in two days from harbor. Freight Smith and Jones 3hp

[@zaheersiddiqui7707]

Very easy and convenient. Thanks

[@TheLabOtomy]

Thanks for the feedback Zaheer

[@firststep7750]

So I switched on my vacuum and it began to smoke. I checked the commutator bars with the lowest resistance and in the four of the tests the resistence couldn't settle on a reading: it would spikes and even show "OL". I didn't need to test given the smoking issue but wanted to know where the problem was. Thanks for the this lesson. It was straight to the point.

[@TheLabOtomy]

Yep, you found your fault!

[@dalemyers6144]

I want to do these tests and hoped to remove the brush holder first. Plastic fan would have to come off first though. I believe the fan was pressed on, Could anyone suggest a good way to remove the fan. It appears to be mounted on a steel collar. Thanks-- Dale

[@realvanman]

To perform this test properly, a four lead, low ohms meter is required at minimum, and much better to use a growler. To properly test for grounds between the windings and the Core, a megger is really required, or at very least set your meter to the Highest ohms setting, Not the lowest. The insulation test need only be performed between ONE commutator bar and the armature Core, because All commutator bars are connected together!

[@yabonjin]

sounds good. Please make a video for us with more explanation!

[@stefanvalchev8066]

"The insulation test need only be performed between ONE commutator bar and the armature Core, because All commutator bars are connected together!" yeah thats the right way.i think he has no idea what is happening

[@wwaldes]

to debil, nie ma mu co tłumaczyć, i tak nie zrozumie

[@MrKromy67]

I appreciate your video very much. Thanks.

[@TheLabOtomy]

Thanks MrKromy67

[@calinsandor9518]

Is this available for cordless tools? today i replaced brushes on my 18 v, dga 452 makita angle cordless grinder, checked the armature (no short circuits), but after reassembling it doesn't run smooth or constant as new, after a few seconds the speed varies for a short period and it comes back again, but has enough power to cut someting. I noticed a little bit of play on the big bearing. What do you think? What should I do? Thanks in advance.

[@TheLabOtomy]

Are the brushes properly / securely seating and making good contact with the commutator?

[@calinsandor9518]

@@TheLabOtomy yes, I even clean with a fine sandpaper the copper contacts and replace the holder with a new one. I will replace soon as posible the 2 armature bearings with 2 new skf.

[@calinsandor9518]

kzbin.info/www/bejne/mGq7qZ-PqtioiJo this is the grinder, I made a video today, it looses rpm in minute 0:25 and returns back for 30 sec, but still oscillate. Never ever dealed with this kind of problem and repaired a lot of my grinders.

[@TheLabOtomy]

@@calinsandor9518 Good to see there are still people taking good care of their stuff! Repair Reuse Recycle!

[@calinsandor9518]

@@TheLabOtomy I do care about my tools. I work with 20 power tools and 10 inverters/welders and I can't afford to throw them away and buy new ones. I repair what I can by myself or at a specialized shop and save a lot of money with a little bit of struggle 🤝🥂

[@saleemkader2126]

what causes overheating of starter on lawn mower., i have glued the magnets back not sure if they have to be in a certain way, mine had 2 magnets .

[@TheLabOtomy]

Difficult to assess without knowing the specifics, but a motor traditionally overheats because it pulls many amps, this due because it has to work hard. This could be due to the operations being conducted (i.e. mowing high grass), or due to mechanical restrictions (worn off bearings, or stuff stuck in the blade). Hope it helps

[@lgsr1]

I used your instructional video to clean and test my armature. Can you tell me the easiest way to clean the shavings from inside that are attached to the magnet? Thank you.

[@TheLabOtomy]

Gently brush them off

[@santiagoriano0126]

gracias por el tiempo que le dedico a hacer el video, muy útil la información.

[@tyronearendse1722]

Nice video good demonstration to test

[@TheLabOtomy]

Thanks Tyrone

[@danoid7998]

I have this exact looking motor on a drill press. When I power it on it hums a little at 0 speed but if I try to increase the speed it shuts my whole press off due to some kind of over temp protection.

[@peterx7623]

Excellent video. Going step by step....again....again. Most youtube videos skip basic steps like setting multimeter before each test and you have to go back to beginning to see what is the multimeter set to . Same thing with measurements....taking two measurements after each other is perfect and enough to show roughly the same reading. Nice work, LabOtomy ! :-)

[@TheLabOtomy]

Thanks for the feedback Peter X, appreciated

[@janzelf]

How to fix it, would be a cool follow up.

[@billb295]

Wow great vid all the info you need

[@TheLabOtomy]

Good to hear, thanks

[@weldmachine]

Good video. Mostly when i see the Armature of an electric motor ? Is when my Angle Grinder stops working. IF the bushes are worn replace them. If Not worn, and the commutator is worn. Then in the bin it goes and off to buy a New Angle Grinder, LOL.

[@khinmaungtun411]

THANKS FOR YOUR SHARING SIR

[@TheLabOtomy]

Most welcome

[@yvestremoulet4752]

very well explained ... bravo ! ;)

[@TheLabOtomy]

Thanks Yves

[@repairchannel]

That was very helpful. Thank you!

[@TheLabOtomy]

Welcome

[@kosti116]

Thx for this video!

[@TheLabOtomy]

Welcome

[@shinosg-wiz4619]

is it possibile to clean a commutator with fuel? mine it's flooded with black oil from the differential

[@carlfischer6363]

General question a starter motor I'm troubleshooting has four brushes each separated by 90 degrees. The brushes as 12 o'clock and 6 o'clock are positive and brushes at 3 o'clock and 9 o'clock are negative. If the armature windings terminate at commutator segments that are 180 degrees apart. How is there current flow? It seems like both ends of the armature windings would be at the same polarity at any given moment. What am I missing?

[@TheLabOtomy]

Commutator segments are not, per se, connected on a 180 degrees direction. It all depends on the motor so can have many different configurations.

[@carlosgomes6074]

May i add, your 3rd Test should also been done on Meg Ohm scale, reading should be higher than 1 megohm. Don't touch the probe ends as you will false readings

[@Trashbg]

it helps me identifying drill motor issue

[@TheLabOtomy]

Nice

[@westinthewest]

If you measure no bar to stack leakage on the first bar, shouldn't that conclude the test? Any leakage from the windings to the stack would show up on all of the bars.

[@RixtronixLAB]

Nice info, thanks

[@josephwachira1176]

its a good video, thank you

[@TheLabOtomy]

Thanks Joseph

[@rubenjoaquincetinaabreu135]

Thank you so much for your video, helps maintenance students a lot

[@TheLabOtomy]

Happy to help

[@KingKasanova]

The commutator bar or the bit you was touching with the prongs. Mine is completely worn down. Does that mean I need a new motor?

[@TheLabOtomy]

This would need to be repaired at least, a specialized shop can refurbish that part if buying a new one is too much of an investment.

[@russellmaguire4316]

Hi great video, how much variance in resistance is acceptable?

[@TheLabOtomy]

Plot the data and see if there are odd spike values or if the chart looks homogeneous

[@llamadeudun8291]

@@TheLabOtomy podrías indicarme como realizas la grafica? Gracias por tu ayuda!!

[@content_blend_hub]

Great👍👍👍👍👍

[@oldmajor338]

THANK YOU!

[@TheLabOtomy]

Welcome

[@herberar]

The format, the graphics, the contents and even the music is very clear and amusing, great !

[@TheLabOtomy]

Thanks for the feedback

[@bibbidi_bobbidi_bacons]

Burn glaze on commutator copper and loud high pitch whine indicate overheating damage requiring rewinding and replacing the commutator?

[@TheLabOtomy]

How are the ball bearings looking? They can also be a source of strange sounds

[@amaralmotores]

No teste de isolamento da massa, deveria ter colocado na escala de 2000k

[@llamadeudun8291]

hola amigo, podrías indicar por que se debe realizar de esta forma? Gracias!

[@fannymdl67]

Buenas Noches... en el caso de confirmar que la armadura esta dañada... La misma no tiene arreglo??? La solución es comprar una nueva???

[@TheLabOtomy]

Algunas personas son especialistas en la revisión de motores eléctricos y pueden reparar un conmutador averiado. Comprar un reemplazo también es una solución.

[@fannymdl67]

@@TheLabOtomy Gracias por darme alternativas, ya solucioné ;)

[@TheLabOtomy]

Gracias por los comentarios, bueno leer

[@brianconcannon822]

To test continuity to ground wrap a braided copper wire around the comm then measure from braid to stack ( ground) it is much faster.

[@TheLabOtomy]

Indeed!

[@geovani60624]

if any of them are shorted to ground it will show in any of them, the resistence may be lower but any value other than open is bad

[@stang_daddy5980]

thank you! using this test procedure now on a used motor i just bought.. do you know the difference in using a growler rather than this? does the growler induce more voltage to make shorts more noticeable? it seems as though this should work about as well.

[@TheLabOtomy]

The growler is a specialized device, so will be faster helping validating the quality of an armature insulation for eventual shorts... this said, being specialized, means it is less common than a standard multi-meter in a work-space... with the multi-meter, I also like to confirm the balancing of the coils, not sure if the growler can deliver on that (leaving the last open for any growler specialist to infirm/confirm on that statement)

[@stang_daddy5980]

thanks again! I ask because I have a motor I need to repair for my race car that is a bit hard to find, one of the people I called for help said a regular multimeter couldn't do the same job even good enough for me in my garage, considering this video and the fact that the part is mine, im going to test it this way and see how that works.

[@philliphall5198]

A grower is the best way

[@upsidediy3945]

You can Definately rewind the wires and use it again. The main problem isn't burnt wires, but the alloy, assembly itself, if it's still in good shape. Electric motors usually have an air cooling fan to them. Sometimes a heat sink or heat resistant shroud , thicker wires can pro long their use. How they short outs, perhaps small metal debris,melted resin, from heavy use .

[@Ano-Nymos]

Hello. Is 1.5 Ohm usual for all motors? Should I only have a current flow of 180 °? Installed in the motor, it is not easy to identify the correct contacts. I am using a metrix MX 355. An ammeter with a combined flow test and ohmmeter. I measure a flow of 4.3-5.3 ohms between many contacts. Do I have to measure all opposite contacts? So far I have found a pair of opposing contacts with no flow. The carbon contacts are as wide as two contacts on the armature. I have the problem that a Sebo Felix vacuum cleaner with Ametek Italia e063200099 1200W motor with good long coals suddenly stopped working. When I put the motor out of the device, it ran sometimes. But not always. Like a loose contact. But one thing is certain, it is not the supply lines, they also have power when the motor is not running. I cleaned the contact surfaces of the anchor and the coals with a bath lime cleaner with sulfamic acid and then solvent, and tried again. Same as before. I can't say whether the "fire" is stronger now. But it seems very strong compared to the Wikipedia video. Is the engine over and need to be replaced? Because a replacement anchor (if it were) is probably not available for purchase. If I make the effort to pull the sheet of the fan chamber down, I could remove the anchor. If I knew where I could get a replacement engine ... Also used. For example, with the names of other devices that contain this motor.

[@TheLabOtomy]

The idea of the 180 test is that you cover the same wire length each time, hence the need to choose consistent pairs of commutator contacts. Any variation around that test is an indication there may be internal shorts and would require either the armature to be replaced or serviced/rewired (specialised work).

[@rickc2222]

Is it ok to do these tests with the armature still mounted in the motor casing with the brushes removed? for insulation test is it ok to just use the motor casing or center shaft instead of the iron stack? should all be connected right? I work on treadmills and removing the armature is wayyyy too time consuming - need a faster way to test motors...

[@TheLabOtomy]

With the brushes removed, that is ok

[@kamelal-bellihy4713]

I have a drill, it’s motor has a cracked magnet, will this affect the performance?

[@TheLabOtomy]

Difficult to say without seeing the extent of the damage

[@lgalhardo]

I'm trying to fix a paper shredder motor, it has one of those rectangular thin plates missing and it caused the brushes to go out of place due to the gap. Is this fixable ? What should I do ?

[@TheLabOtomy]

Constant contact with the brushes is essential for good motor operations, so unless you can figure out how to replace (build one yourself?) the missing piece, the shredder will not operate properly...

[@lgalhardo]

@@TheLabOtomy I think that rectangular thin plate missing it's called the commutator. From what I understand, one (or two) small wires should be connected to it (or a single wire passing thru it, since it was ripped off I ended up with 2 wire ends. This is too small to see properly, need to check better with a magnifying glass, but I think the commutators have a wire passing thru them, right ? I could try to get a pice of copper and shape it to fill the missing gap and connect the wire(s). This is an AC motor 220v, not sure if soldering the wire(s) to the hand made missing commutator, glued with high temperature epoxy would withstand the temperature when working. What do you think ?

[@TheLabOtomy]

Seems like a delicate repair, but since the shredder is useless at this stage, may be worth a try

[@jote2275]

You can run this type of motor on a very low d.c. voltage to test it. A vacuum cleaner motor wil run on 9 to 12 volt d.c.! The rpm is of course not high than. Be careful and do not connect it to a car battery. Dangerous when short circuit! Vacuum cleaner motors without electronics in it to change the power of the suction, you can supply direct on 9 volts to get it run. Try it yourself.

[@dunand76]

Thanks>>>>Subscribed!!!

[@dannypal123]

I have several broken motors, and I find this video instructional because at least I can tell for certain that the motor is irreparable, (something that I already well figured out, as the vacuum cleaner does not clean and the hair dryer does not move air). The video is very well done (artistic, indeed), and I've been hoping it could give me a hint on how to fix the coils by the bottom stack, but I don't think this is feasible with my limited capacities. Like an egg and myself, my coils and brain are fried, it seems... Nevertheless, the little funnies help me shed off the tears of what is now just a lump of metal... Next, LabOtomy, sir, would you kindly show us how to actually *fix* the f'in thing? Much appreciated, D.P.

[@TheLabOtomy]

Thanks for the input, will think about it

[@ericsnyder3689]

At least a comment as to is it worth repairing. For most it isn't but some of us like that challenge. Why not....

[@Mad_Scientist2052]

@@ericsnyder3689 Excellent attitude!

[@suryononangkring]

Sangat membantu , terimakasih infonya

[@yabonjin]

So what is the conclusion? What does one do next? Must I rewind or else scrap?

[@TheLabOtomy]

Correct, rewind or scrap (or find replacement)

[@irishguy200007]

What should the resistance be after deducting the lead resistance?

[@TheLabOtomy]

As mentioned in my other answer to your questions, there is no 1 answer as all motors are different (in number of winding loops, winding design & patterns, motor sizes, winding wire gauges etc). If you really need a value, those should be found in the product specs (if available)

[@intestinalworm1202]

Great video - has got me thinking! Hi, testing a 6-pin universal 2-pole Bosch washing machine motor (Bosch front loader). The motor had previously seized due to a failed armature bearing. Replaced both bearings on the armature. I then checked the motor for continuity through windings, thermal fuse, to the carbon brushes and through the tacho - all appeared good according to the DMM. So, reinstalled the motor in the machine and tested, but now the motor fires up and spins the drum as you would expect, but only for just a second or so before it stops (this happens for wash, rinse and spin)??? Could this be a commutator issue as per your tests above or would any failings (shorts) here cause the motor not to spin at all)?

[@alloverflorida5886]

Sounds like the start capacitor is working but the run capacitor has failed possibly

[@intestinalworm1202]

@@alloverflorida5886 Thanks my friend! I know where the start capacitor is and I checked it for obvious signs of failure early on - not sure where the run capacitor is though?

[@johndoer903]

@@intestinalworm1202 many times they are both in the same case.

[@duramax78]

My vacuum cleaner turns off after about 20 seconds, and if I keep using it that time goes down, I gotta wait about a minute in between, It also happens when I hook the motor directly too power, brushes are good, would you have any ider where I could look next.? TIA.

[@west_park7993]

i have a small electric motor on a child toy peg pelegro polaris. one motor is fine, the other does not have power. Took them off the gear mechanism, both turn, but one stops as soon as power is disconnected, and the other spins freely. no mechanical resistance. lube does not help. i took apart the the bad one, one coil is darker, obviously overheating. but not shortened. i measured the resistivity of all 3 coils, they start at 3-4 ohmes, then quickly reduce to 0.8 ohm. makes sense. Any idea, what is wrong with this motor? I bought a replacement, but this is my curiosity tickling me.

[@TheLabOtomy]

Dark is a bad sign, heat can cause isolation material to internally fail and the coil to propose a shorter electric path (implying a different magnetic field is generated that may longer cause the motor to improperly turn)

[@west_park7993]

@@TheLabOtomy thats what i thought, but the conductivity of the 3 coils is the same. unless the shortage is between dark coil and armature

[@teletronicsnanquil601]

Where is the location or your shop..

[@TheLabOtomy]

Second street left

[@hermanswartbooi1850]

Hallo sir i got a small black and decker drill with a ten millimeter chuck it runs with a deep noise and very slow,what can be faulty or how can i fixed it

[@TheLabOtomy]

Broken ball bearings?

[@5onCover]

Thank you SO much for posting this video. I have an vintage sewing machine that is not starting up when I plug it in. Hopefully it's a short in the wires or wires not connected properly and not the commutator/aperture.

[@leynagh]

It's got a plug ? That's not vintage. Vintage is the Old treadle operated Singer machine my Mother used to rattle away on when we were kids. . . .

[@poolman8676]

So when I would did the bar to bar it went down from 1.4 to 1.3. not a big difference but it still changed. Does that indicate a problem?

[@llamadeudun8291]

no amigo, por ejemplo una diferencia entre una lectura y la otra podría ser 1.4 a 3.5, o valores que están mu separados, ya seria preocupante.

[@StAlKeRrEpAcK]

Mine gave me 40ohm is it good or bad the wires look darker in color and fuse keep blowing

[@TheLabOtomy]

I could be wrong but to me, fuse blowing would indicate an issue with another section of the machine, like damaged wiring or a blown decoupling capacitor

[@StAlKeRrEpAcK]

@@TheLabOtomy the motor is for hand blender dc 220v the fuse doesn't blow when motor disconnected but when i connect motor and turn it on motor runs for 3 seconds then spikes and blow the fuse

[@liviudaniel5082]

nice video

[@shelby50411]

Hi.. i have a craftsmsn router keeps turning off due to sparks..i took apart and filed the commutator good on a lathe and then i flattened the brushes good and now it works a bit better but powers off at high rpm setting...sparks...anyone have any suggestions..brushes are about 1/2 in long

[@viswanathancr2801]

good video

[@TheLabOtomy]

Thanks man

[@elmotengineer9903]

Good job

[@TheLabOtomy]

Thanks

[@g.j.dutoit4447]

Realy hope someone can help me. When i test a armature commutator i set multimeter to 20M ohms then 1 wire on shaft and other wire on commutator, then get reading. Is this mean there is a short between ground and commutator? When set it on lower ohms i not get any reading. Just when set it on 20M ohms and 200M ohms i get reading.

[@garrygemmell5676]

Excellent tutorial I have learned something new today - always a good day!

[@TheLabOtomy]

Thanks for the feedback

[@arudayo]

Very practical and helpful....thank you

[@augustinechinnappanmuthria7042]

Super 💓

[@TheLabOtomy]

Thanks

[@yoruhana190]

Best video on this topic. And a nice disclaimer. My field is black and has almost no insulation left. The armature has one suspicious coil. All of them are 0.3 to 0.5 but one is 0.6 , could it be normal or could this even be the reason why the field overheated? I dont know nothing obout the provious use of the mashine. It's a 15yr old dewalt but the blade was pretty dull.

[@TheLabOtomy]

So, a possible scenario in your case could have been: 1) Blade is dull, which causes 2) Motor to have to work harder, which causes 3) Motor to pull more amps, which causes 4) Armature coil to heat up beyond normal, which causes 5) Damage to the internal wiring (resulting in resistance discrepancy within the machine coils, 0.3 to 0.6 is a 100% variation which is real source of concern) and degradation to the insulation material (burning through and truning black) 6) Which causes the motor perceiving a loss of power to go back to 3) for a ultimate catastrophic failure The Cause and effect theory at its best!

[@Mad_Scientist2052]

@@TheLabOtomy I could not have explained that better. Got an old dremel here that's got the same variance. I just happen to have some rolls of magnet wire that's just a little thicker than what's on it now. Time to rewind the armature and field core. Why would I do this? Because I can!! And just a little payback for pissing me off and failing when I needed it most! And from what I understand this particular model is known for this failure, and I am surprised that with this being a flex shaft only model they would have used a better quality wire and cooling fan! In any case, Thank you for this informative video👊

[@bitetime4266]

My multimeter indicates 0.4 ohm resistance between probes and between commutator segments, so resistance cant drop more. How should i know if there is short between coils?

[@martinforster8709]

easy to follow video, great work!

[@TheLabOtomy]

Glad you liked it!

[@markrainford1219]

Before you bin it though. Try scraping out the slots between commutator segments with a piece of sharp metal that fits the gap.

[@TheLabOtomy]

Thanks mark for the tip. What would you do the with the mica you extract?

[@oliverelmes179]

hola cual es la resistencia que tiene que tener como minimo gracias

[@llamadeudun8291]

tengo entendido que no deben variar entre ellas, ice el video que el valor es irrelevante pero que deben ser similares

[@oliverelmes179]

@@llamadeudun8291 ya ok

[@subhashnakkanaboina]

Nice discription below the video tq

[@TheLabOtomy]

Thanks

[@marantala.7268]

Boss ngawa kaba ng old cercolar saw 100 volts

[@irishguy200007]

What's a healthy resistance and what's a bad resistance?

[@TheLabOtomy]

There is no good or bad resistance (number of winding loops, winding design & patterns, motor sizes, winding wire gauges can all vary), it is all about being balanced across all segments so that the electromagnetic forces exercised are consistent to ensure a smooth rotation.

[@irishguy200007]

@@TheLabOtomy If the laminate comming on wire is damaged then would itbe possible for a number of windings to be shorted to it's neighbouring windings?

[@TheLabOtomy]

That is possible, the tests in the video can then show you a path imbalance

[@jessecampbell4580]

Can anyone tell me why is there continuity between the comutator segments? Why are motors built this way? I thought comutators were suppose to separate the current, sending it through a different coil every time the brushes jump to the next segment?

[@jessecampbell4580]

I understand why the segments are connected directly opposite each other, just not right next to each other.

[@तोॆोीदपगुपेगुपू]

very good

[@TheLabOtomy]

Thanks

[@lycanlycans7548]

Thanks so much for your video ! It saved my day ! Best regards,

[@TheLabOtomy]

Good to read, thanks for the feedback

[@MultiBegbeg]

Bonjour , j ai un moteur des fils de cuivre son noir es ce que c est normal ? !

[@zondepa5537]

Great Video! I have one question. In the first testing you had appx. 01.6 ohm and you said that there is resistence drop? How do you indicate that? For examle if you measure it and it jumps right away to 01.6 ohm instead of droping from 34.6 to .01.6?

[@chrisbart5316]

I am not the author, but I am an electronics technician. The rate of drop is immaterial, as it is a function of the circuitry in the meter, and also any residual resistance at the contact points. Just wait, and use the reading when the meter settles. The term "drop" as applied to this test is about the amount of resistance in the armature winding, which will cause a voltage drop when power is applied.

[@pawemik7975]

Dziękuję bardzo, skorzystałem!!!

[@happymann839]

Ausgezeichnet 👍👍👍👍👍

[@TheLabOtomy]

Dank!

[@diegosegovia1961]

Esa es solo una prueba, pero hay ocasiones que aperentan que todas las delgas están bien porque dan continuidad y están en cortocircuito por dentro, y eso solo lo comprobas con prueba de megger si la segeta vibra encima de él esta dañado.

[@Ruf777]

Пошкодження таким робом можна і не виявити, бо не по окремій ламелі треба перевіряти, а прикладати щуп з однієї сторони на декілька ламелій і з іншої також другий щуп і обертати якір навколо себе (щупи повинні бути розташовані перпендикулярно до ламелів), при обертанні значення опору (Ом) не повинні змінюватись. Таким чим чином ми взнаємо чи горів якір чи ні, хоч при окремому заміру точковому ламелів тестер може показувати що все в порядку.

[@mitrovdan]

Very clear and simple explanation. Thank you definitely helpfull.

[@TheLabOtomy]

Great to hear!

[@sudheerrs5856]

@@TheLabOtomy hello sir As i tested same u told in video We have 180v dc motor rpm is 1000.....rpm is flacuating around 300+or-.when rpm is 1000 1. Cleaned the comutator. 2.fixed new carbon brush 3.at starting rmp is constant after when carbon brushes are slightly corved inside starts flactuating Thank u

[@piecetoyou8285]

Hi,ive taken the brushes out of my washing machine and moved the motor to the bench,the armature only moves about 5 mm to the left and to the right,and it cant move either way any more,any help please what may be wrong,

[@TheLabOtomy]

Busted bearings?

[@piecetoyou8285]

@@TheLabOtomy Thank you i found that out i hour later,but thanks anyway

[@TheLabOtomy]

Cool! Good luck with the repair!

[@zan4637]

I got resistance spike in bar to bar, can it be fix?

[@ostadkaar4763]

good clip

[@TheLabOtomy]

Thanks

[@birkrollo5167]

Could you repair such a motor? And how?

[@TheLabOtomy]

Specialist work I'm afraid, some shops are specialised in electro motor reconditioning

[@C3LM4RFG]

Very good

[@TheLabOtomy]

Thx