problem with the table saw motor. Please help! - Page 1
Forum section: electronics / repair

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 05:21:11 pm
content: Hello,I have a table saw and just 2 days ago when I was running it and turned it off, it gave off this flash from the engine - something it never done before. I think the armature may be worn out and as such need a good clean but could it be anything else?I am grateful for any and all advice on this.Thanks

author: CaptDon
author_rank: Super Contributor
timestamp: November 12, 2022, 06:30:20 pm
content: I would guess that is one of those saws where when you release the switch it dead shorts the motor to bring the bade to a quick stop. The surge current is very high but only briefly. If it runs o.k. I wouldn't even worry about it. If it doesn't run well it's time to replace it!!

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 06:39:57 pm
content: Ok so you're saying that the current may be the issue.. how about the commutator? Because I was thinking that it may have been worn out and that's why it's flashing and whatnots.. .

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 06:42:14 pm
content: ..also i should have mentioned that this flashing thing happened only for the last few days.. In the past few weeks I've been running a lot of timber through it 2 by 6 and 2 by 8s.. and the teeth of the then saw blade was 80. I've seen replaced it with a new blade with 40 teeth.I appreciate any help you can give me. The flash at the end is what concerns me.

author: themadhippy
author_rank: Super Contributor
timestamp: November 12, 2022, 06:45:35 pm
content: id be tempted to whip the brushes out

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 06:52:56 pm
content: you mean sandpaper the commutator? with fine sandpaper slip? say p180?

author: Gyro
author_rank: Super Contributor
timestamp: November 12, 2022, 06:53:57 pm
content: Welcome to the forum.Brushed motors like that draw huge current surges when they start up, especially with the inertia of the blade and often produce displays like that. It looks as if yours has an electric / electronic brake too (I think they all do these days) that shorts the motor when you turn it off. This also cause a high surge current through the brushes as the motor works as a generator.As you have the motor open, I would just check the motor brushes. If the saw has a lot of hours on it they may be excessively worn. The commutator will probably have some wear marks on it but trying to smooth it out just removes more copper. You can also introduce burrs and embed abrasive material from sandpaper. It is normally best left alone.Edit: Are the brushes removeable via screwed plugs on the sides, if not, it may be difficult to put the armature back in.

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 07:05:16 pm
content: Thank you man!But what about the flash at the end? That is my main concern. Will it go away if I let it be? I mean I am no tech genius but I do have a few brain cells and I know that problems left alone tend to fester and grow as a result. In my case, I may lose the entire motor and hence that's not good. (especially considering the money I put on dewalt saw blade with them 40teeth I was mentioning before).Apprecaite all the help I get, I just want this thing to work like before.

author: Gyro
author_rank: Super Contributor
timestamp: November 12, 2022, 07:07:58 pm
content: The flash at the end is the elecroic brake shorting the motor. How accessible are the brushes?

author: Kleinstein
author_rank: Super Contributor
timestamp: November 12, 2022, 07:16:33 pm
content: Some sparking is normal for a brushed motor, especially at high current like at start or with a rather abrupt breake.It is possible that dust is somewhat empeding the movement of the brushes and this can also cause stronger sparks.So it may be worth taking them out and remove dust. It help to put them back in the same orientaion as they were.

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 07:32:30 pm
content: well I tried to open it up today but was unable despite having unscrewed all the screws and wahtnots. I could have forced it but chose not to. I am going to have to open it up and se what's going on inside next. But I am not a techie - I am a tax lawyer - so it's somewhat challenging....

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 07:35:12 pm
content: that's a very good point as I was in a condensed/ no ventilation area the day the flash came about and I can (and really hope) that it's the partical dust from the using the sae.. tree dust.. .but do you think that explains the flash at the end? It's the flash I amabout

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 07:39:09 pm
content: the saw is Ernst As G250. Here is the manual. read it cover to cover. 12cm or less use a stick push. and the distance between the blade guard and blade must be within 3-8mm..https://www.yumpu.com/en/document/read/5913088/gjerde-250-ernex

author: Gyro
author_rank: Super Contributor
timestamp: November 12, 2022, 07:41:09 pm
content: Quote from: centermin on November 12, 2022, 07:32:30 pmIf you've changed blades and been doing a lot of cutting it could well just be dust. If there are no screw plugs to access the brushes then you could try vaccuming or compressed air if you have it.As thetax lawyersdoctors say, firstly, do no harm.

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 07:43:37 pm
content: HAHA...But so I understand it right, you would not take it apart and use sandpaper p180 (a fine paper strip) to rinse the commutator? Only thing I should do is to use compressed air or vaccum it out from the back?

author: Gyro
author_rank: Super Contributor
timestamp: November 12, 2022, 07:46:01 pm
content: Yes, that's what I would say. Any chance of a side view (narrow side) of the motor? - You still haven't said whether the brushes are separately accessible.

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 07:52:16 pm
content: Quote from: Gyro on November 12, 2022, 07:46:01 pmOk I understand. No the brushes are not easily accessible as I tried to take them out today and I could not do it. I unscrewed all the screws and whatnots but no.. nothing happend. I DO WANT to open the motor housing case and be able to put in the vaccum cleaner and suck whatever it is that got in but I dont know how.. I guess I have to work on that tonight. look at some videos and read some more instructions.. .Do you have any idea on how to do it? I have unscrewed all the screws.. the ones visible.. I dont see any more screws beyond them.

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 07:54:27 pm
content: Quote from: Gyro on November 12, 2022, 07:46:01 pm

author: themadhippy
author_rank: Super Contributor
timestamp: November 12, 2022, 08:00:39 pm
content: that top picture shows what suspiciously looks like a brush hole,is there another like it on the other side? and what came out of there?

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 08:02:56 pm
content: Quote from: themadhippy on November 12, 2022, 08:00:39 pmYaap! and I cleaned it with sandpaper today.

author: Gyro
author_rank: Super Contributor
timestamp: November 12, 2022, 08:04:29 pm
content: Those two screws allow the outer stator (field winding and laminated steel core) of the motor to be removed, however you probably need to remove the press fitted fan to remove them.I would seriously advise against trying to get the armature out. The brushes are under spring pressure and will spring to the center of the housing when you remove the armature (assuming that they don't snag on the bottom bearing). Removing it with no clear indication of how to re-assemble it seems like a bad idea.EDIT: Oh, you do have the brushes out! In that case it ought to be possible to pull the armature out, the bottom bearing is probably just a tight fit in the housing. From the view down the brush hole, the comutator looks to be in good condition - no need to remove the armature to clean or smooth it. What do the brushes look like?EDIT 1: A good rule of thumb for brush wear. If the brush is wider than it is long, then it is worn.

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 08:10:15 pm
content: Quote from: Gyro on November 12, 2022, 08:04:29 pmI really appreciate you input and just one last question - my main question. What about the flash at the end? Or will the vaccum cleaner take care of it or some compressed air? I just like that to be gone.. I dont like how it flashed man.. it looks spookey. this is 1800W and I am over it for 5-6 hours a time

author: Gyro
author_rank: Super Contributor
timestamp: November 12, 2022, 08:14:09 pm
content: That sort of compact high power motor is always going to spark when it is being started or braked. Vacuuming out any dust through the grill is as well as you can do. Even corrdless brushed drills flash when you stop them suddenly.Photo of the brushes?

author: themadhippy
author_rank: Super Contributor
timestamp: November 12, 2022, 08:14:17 pm
content: I wouldnt strip it any further,instead get a pencil eraser ,like a pencil but with a rubber in the middle instead of lead,and put it down the brush hole,rotate the motor by hand whilst wiggling the rubber,then give it a good blast of compressed air to get rid of any lefty over debris.The rubber does a surprisingly good job of getting rid of carbon build up without scratching the copper.

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 08:17:43 pm
content: Quote from: themadhippy on November 12, 2022, 08:14:17 pmok. I will do that and report back with the results. But ultimately i need the flash to go away and I agree with start small. Incrementally.

author: Gyro
author_rank: Super Contributor
timestamp: November 12, 2022, 08:19:11 pm
content: I think a thin carbon film on the commutator is a normal and good thing. If you remove it, it will only have to re-form. I would prefer that to possible rubber residue.

author: centermin
author_rank: Contributor
timestamp: November 12, 2022, 08:21:34 pm
content: Quote from: Gyro on November 12, 2022, 08:19:11 pmOk. I will be in touch over the coming days with more update. and I will make more videos and pictures.

author: themadhippy
author_rank: Super Contributor
timestamp: November 12, 2022, 10:12:54 pm
content: Quoteuntil it builds up enough to track between the segmentsQuotehence why you give it a good blast with air

author: coppercone2
author_rank: Super Contributor
timestamp: November 12, 2022, 10:45:37 pm
content: you can also try a fine grit silicone rubber abrasive, which is like a pencil eraser with sand in it. If you get a very fine grit it will clean better then pure rubber and also do minimal scratching. But you need to clean very well after, like nylon brush and flushFYI I noticed that with carbon sometimes if you clean them, the motor will run very hot and loaded for a short period of time, until it gets some kind of minimum wear level that lets it run smooth. So run it on no load first for a while, then light duty cutting a few pieces, so everything gets into initial order. I think its like self lapping/lubricating/etc.

author: andy3055
author_rank: Super Contributor
timestamp: November 13, 2022, 03:01:40 am
content: Quote from: centermin on November 12, 2022, 07:35:12 pmLooking at the view of the back of the motor, if you remove the 2 screws holding the cable clamps, does it also open the cover there? If so, you can tap the motor shaft and the armature should come out the other end (after removing the brushes).If you can get the armature out, you can use a very fine Emory cloth to polish the commutator.

author: Gregg
author_rank: Super Contributor
timestamp: November 13, 2022, 03:39:04 am
content: If you can remove the back cover (after removing the brushes, of course), check the bearing for and where it seats in the back housing for wear and possible misalignment. If the armature is sagging such that the brushes are not directly opposite anymore, it be the cause of your problems.

author: james_s
author_rank: Super Contributor
timestamp: November 13, 2022, 04:08:05 am
content: Quote from: centermin on November 12, 2022, 06:52:56 pmYou should never sand a commutator, when they are resurfaced a diamond lathe is used to get a very smooth finish. This is rarely necessary though, usually all you have to do is clean the carbon dust out from between the segments and replace the brushes when they become too short.

author: Gyro
author_rank: Super Contributor
timestamp: November 13, 2022, 10:39:15 am
content: There's nothing wrong with the commutator. From the photo in reply #17 you can see that it is reasonably clean and the visible segment gap is clear (I don't see why the others would be any different). It is not flashing over while running, just showing visible sparks when the electic brake shorts it, as you would expect. We shouldn't be encouraging the OP to engage in unnecessary and potentially damaging actions.I'm more concerned about the brushes. In reply #19 he seems to indicate that he cleaned them with sandpaper, potentially embedding abrasive material and spoiling the nicely bedded curvature of their ends. We don't yet have any photo or indication of the degree of wear or damage done to them. It might be a case for fitting new ones anyway, not that it will stop the sparking when the brake cuts in, that's just a fact of life.

author: centermin
author_rank: Contributor
timestamp: November 13, 2022, 02:00:34 pm
content: Quote from: andy3055 on November 13, 2022, 03:01:40 amwell I removed all the screws I could find and no.. the brushes could not be removed and i could only wiggle it a bit no more... those two screws are just holding the wire.. do you have any suggestion how i could open it? because I NEED to open it and take the commutator out. All this talk about sanding this and rubber that is nice and dandy but at some point I need to take it out to see for my self.

author: centermin
author_rank: Contributor
timestamp: November 13, 2022, 02:02:33 pm
content: Quote from: Gregg on November 13, 2022, 03:39:04 amI have removed all the screws but still the back cover does not come off. any suggestion as how to proceed?

author: centermin
author_rank: Contributor
timestamp: November 13, 2022, 02:05:25 pm
content: Quote from: james_s on November 13, 2022, 04:08:05 ambut there is alot of videos on the internet guys showing that sanding the commutator will reduce/ if not completely end the sparks from the motor... there is one guy, i think thai or phlipino .. he's crazy with it. if it's dirty and the fine film on the copper is too think.. what then?

author: centermin
author_rank: Contributor
timestamp: November 13, 2022, 02:09:05 pm
content: Quote from: Gyro on November 13, 2022, 10:39:15 amhaha.. you sound like my mom when I got a new multimeter and i use to stick it into any and all holes to "check the pulse" hahahha.. she became real crazy when i had it with me for dinner... checking the cutlery....yes, i did sand it a bit but not much and it was a curve and i maintained that curve.. it was burned on the one side.

author: themadhippy
author_rank: Super Contributor
timestamp: November 13, 2022, 03:34:12 pm
content: Theres no need to strip it down further,uless you want to cause more problems.chuck it all back together,put in some new brushes and maybe enjoy the free firework display every time you switch it off

author: andy3055
author_rank: Super Contributor
timestamp: November 13, 2022, 04:53:07 pm
content: Quote from: themadhippy on November 13, 2022, 03:34:12 pmThat is a good thought. It is possible that the wear on the brushes has come to a point that they are just making enough contact to run the motor. If you put in new brushes, the springs will be under more pressure and it will make better contact. That might do the trick. Good call!

author: centermin
author_rank: Contributor
timestamp: November 13, 2022, 05:08:50 pm
content: Quote from: andy3055 on November 13, 2022, 04:53:07 pmSo how does it relate to my situation? basically do nothing? just blow some air into it and hope for the best?

author: centermin
author_rank: Contributor
timestamp: November 13, 2022, 05:13:04 pm
content: Quote from: themadhippy on November 13, 2022, 03:34:12 pmi'll tell you man I like fireworks just like any other guy but having a firework on your tablesaw is not pretty scene. Besides, these fireworks did not exist just 4 days ago. Why would I want to live with this? It's like taking a leak in your pants in the middle of winter.. it's fine and dandy in the beggining but then the cold makes it all messy and you feel like a 10 year old self and having been sent home by the teachers. I am just saying man... I dont like the fire..

author: Gyro
author_rank: Super Contributor
timestamp: November 13, 2022, 05:53:44 pm
content: It's fine. In all likelyhood, it's always done it, especially before the brushes had bedded in. You were probably just using it in an enclosed space and saw the flash, where before you were concentrating on what was happening on top.Sandpapering the commutator, or anything that roughens the surfaces will just make it spark worse. Just show us a picture of the two brushes that you removed.

author: centermin
author_rank: Contributor
timestamp: November 13, 2022, 05:57:38 pm
content: Quote from: Gyro on November 13, 2022, 05:53:44 pmI'll snap some pictures of the brushes and vaccum/ air pump the motor in the morning. you'll have pictures and I REALLY hope you're right because thinking of the alternative is not fun.

author: andy3055
author_rank: Super Contributor
timestamp: November 13, 2022, 09:10:36 pm
content: Quote from: centermin on November 13, 2022, 05:08:50 pmWhen the brushes wear out the contact pressures between them and the comutator lessons and at a certain point, the spark will become more prominent due to the gap widening. New brushes will be longer and there will be more pressure from the springs and less of a spark accordingly.

author: centermin
author_rank: Contributor
timestamp: November 13, 2022, 09:43:33 pm
content: Quote from: andy3055 on November 13, 2022, 09:10:36 pm

author: centermin
author_rank: Contributor
timestamp: November 14, 2022, 06:10:19 pm
content: pic of brush

author: centermin
author_rank: Contributor
timestamp: November 14, 2022, 06:11:01 pm
content: pic 2 of brush

author: centermin
author_rank: Contributor
timestamp: November 14, 2022, 06:12:10 pm
content: pic3 of brush

author: centermin
author_rank: Contributor
timestamp: November 14, 2022, 06:13:56 pm
content: pic4 of brush et al.

author: Gyro
author_rank: Super Contributor
timestamp: November 14, 2022, 08:58:27 pm
content: That saw certainly gives the motor some punishment when the brake cuts in! You can also hear it in the rate of decceleration.One think I can say for sure, those brushes are badly worn. Using my rule of thumb, the length must always be significantly longer that the width. Those are much shorter, leading to the brushes tilting in the holders (you can see that from the end profile), whch also accelerates wear even more. You definitely need to replace them!Hopefully with the increased contact pressure and stability of new brushes, things will look significantly better.

author: centermin
author_rank: Contributor
timestamp: November 14, 2022, 09:40:02 pm
content: Quote from: Gyro on November 14, 2022, 08:58:27 pmwell what kind of brush should I buy? I've browsed the internet and there is plenty of different types of brushes and longer than width is nice rule of thumb but is there any other aspect I should keep in mind? Thanks

author: Gyro
author_rank: Super Contributor
timestamp: November 14, 2022, 10:33:28 pm
content: If you can't find spare brushes directly from the manufacturer, try the user manual - imported stuff often has an exploded parts diagram with parts list.If looking for generic replacements then the dimensions you need to measure are the brush width and thickness (these will determine the fit in the holders) and also a visual match of the brass plate that fits under the plastic screw cap. You will probably find that there are a only a couple of length options for the other dimensions, and you will probably be surprised by how much longer new ones are. Motor brushes are fairly standard.

author: andy3055
author_rank: Super Contributor
timestamp: November 15, 2022, 12:01:01 am
content: I just saw the pictures of the brushes and I must say you just about saved that motor as they seem to be worn out at least 70%. They seem to be the little harder type with some sort of copper and carbon mix I have seen. Definitely not the carbon only brushes that are much softer.

author: centermin
author_rank: Contributor
timestamp: November 15, 2022, 06:08:18 am
content: Quote from: andy3055 on November 15, 2022, 12:01:01 amSo you think if i change the brushes then I'll be fine especially with respect to the flash at the end when i turn the motor off? If that's the case I am more than grateful!!!

author: andy3055
author_rank: Super Contributor
timestamp: November 15, 2022, 06:21:05 am
content: The reasoning is that shorter brushes make loose contact. Do you know what happens when you have loose contacts in an electrical circuit?Also, if it was me, I would not use those brushes at this point. There is no better way to tell you that they need to be replaced. End of story!

author: centermin
author_rank: Contributor
timestamp: November 15, 2022, 07:17:54 pm
content: Quote from: andy3055 on November 15, 2022, 06:21:05 amI really appreciate your candor as I, sometime, can be a bit senile and have hard time what's going on.I will replace them and let you know what's what.Thank you!

author: james_s
author_rank: Super Contributor
timestamp: November 15, 2022, 09:37:27 pm
content: Quote from: Gyro on November 14, 2022, 08:58:27 pmI think I would modify that by increasing the braking resistance, or just remove the braking entirely. The saws I've owned are all old enough to not have a brake to begin with, it's fine, just don't touch the blade.

author: Gyro
author_rank: Super Contributor
timestamp: November 15, 2022, 10:14:46 pm
content: I wondered about that too, but I think it would be going past the OP's capabilities.

author: CaptDon
author_rank: Super Contributor
timestamp: November 16, 2022, 01:51:07 am
content: What do you mean "What kind of brushes should I replace them with"? For Christ sake get a set from the original equipment manufacturer. They should be readily available replacement parts. Brushes wear and are meant to be serviced. It's a law of nature. For something as simple as a commutator and a pair of brushes in a standard production saw......I haven't seen this much verbal banter since Trump claimed the election was stolen.

author: centermin
author_rank: Contributor
timestamp: November 16, 2022, 08:41:05 am
content: Quote from: CaptDon on November 16, 2022, 01:51:07 amYou're a funny man! Hahah.. My gf always tells me that I am stupid but she is more pointant and you Sir, are eloquent.