Poorly Angle Grinder

[rtcosic]

My small Makita angle grinder suddenly slowed down, got warm and emitted a few wisps of smoke before I turned it off.

I've checked the brushes and the visible part of the armature which are fine. I've blown it out with compressed air. It turns easily and smoothly by hand.

I spoke to it nicely and started it but more smoke.

Are there any useful diagnostics I can do with a basic multi meter? If I do find something is it likely to be repairable? Last time I checked replacing stator or armature was not economically viable for this small single speed model.

 

[sg66]

When my Milwaukee went the electronic control assy was more than a new grinder....as much as I hate throwing things away it just made no sense considering the work it has done.

 

[rtcosic]

When my Milwaukee went the electronic control assy was more than a new grinder....as much as I hate throwing things away it just made no sense considering the work it has done.

I have a much older more powerful variable speed and soft start Makita too.
It has ceased working and the problem 'may' be the electronic speed control. As I am not certain I'm reluctant to pay the price of a replacement part.

It still lives in the box with the other grinders in the vain hope it might get better with a bit of a rest.

 

[Kram]

Mains grinder? Smoke is likely the winding insulation. It may be a section has shorted, causing more heat and more smoke.
If you can identify the burnt section, it may be possible to coat in insulating resin to repair it, if you have caught it early enough.

Otherwise could be a filter capacitor, they can make large amounts of smoke and usually smell much worse.

 

[rtcosic]

Mains grinder? .........

Otherwise could be a filter capacitor, they can make large amounts of smoke and usually smell much worse.

Yes, 220V

What would this filter capacitor look like? Small rectangular things? Would it show external evidence?

If it's the windings then it's onto Facebook Marketplace spares or repair to save me the effort of going to the Civic Amenity Site.

 

[tigdlo]

When my Milwaukee went the electronic control assy was more than a new grinder....as much as I hate throwing things away it just made no sense considering the work it has done.

Makita spares are often good value and more readily available than other brands, one of the reasons I stick with them, the cheapest tools from any of the brands will always be an exception.

If you can identify the burnt section, it may be possible to coat in insulating resin to repair it, if you have caught it early enough.

I did this with one of the 2 failed Parkside grinders I have, it appears to have worked but time will tell for sure, my symptoms were different, I was getting intermittent arcing on one of the brushes then it would cut out completely but would restart a few minutes later. It hadn't let the smoke out, if yours has then it might be a bit late

I have a much older more powerful variable speed and soft start Makita too.
It has ceased working and the problem 'may' be the electronic speed control. As I am not certain I'm reluctant to pay the price of a replacement part.

The speed controller/soft start PCB went with a bang on my other failed Parkside grinder, I have bypassed it for now and it works fine, could be worth doing on yours if you don't want to gamble on new parts.

 

[Kram]

Any time theres brush issues I would be checking the spring, it can also be poor contact and will cause a lot of heating.

 

[Agroshield]

What would this filter capacitor look like? Small rectangular things?

Yes. And they are only there for suppression purposes (i.e. so they do not interfere with the TV). So you can disconnect it completely from circuit to confimr the remainder of the machine is OK or not.

What model is it? We can find the exploded diagram and make suggestions.

What model is the soft start one? The other advantage of Makita is their twin Fakita brand, for which a soft start switch would be available very cheaply.

 

[RWD3M]

Otherwise could be a filter capacitor, they can make large amounts of smoke and usually smell much worse.

This ^^^ Happened on my Bosch. Replaced with a new one from Bosch and all is well again.

Thinking about it, I had a similar think on my Vax a few years back. Same, replaced witha new one and still going strong.

 

[rtcosic]

Yes. And they are only there for suppression purposes (i.e. so they do not interfere with the TV). So you can disconnect it completely from circuit to confimr the remainder of the machine is OK or not.

What model is it? We can find the exploded diagram and make suggestions.

What model is the soft start one? The other advantage of Makita is their twin Fakita brand, for which a soft start switch would be available very cheaply.

Photograph of the little one and the capacitor.
The model 'plate' is worn off.
I'll perform a more in depth autopsy and look for what? Scorched wires?

The larger one is 9564PCV. It was dear!
I'll open it up again and take a brave pill and try direct wiring to bypass the switchgear.

 

[rtcosic]

Any time theres brush issues I would be checking the spring, it can also be poor contact and will cause a lot of heating.

Brushes about 8mm long, clean and free moving. Spring is taught and not binding. No sparks, just smoke from the vents.

I removed the brushes from their housing and cleaned the whole area with brake cleaner before reassembly and retesting.

I ruled out the brushes on that basis.

 

[rtcosic]

The speed controller/soft start PCB went with a bang on my other failed Parkside grinder, I have bypassed it for now and it works fine, could be worth doing on yours if you don't want to gamble on new parts.

Off to source my brave pill and will proceed with this test.

 

[gaz1]

if the motor is bust strip it and keep the spindle and gearbox as you can do a few things with them

 

[rtcosic]

Starting with the little one:
Rotor:

Zooming in on the suspicious lack of insulation at each end:

So, oh Forum Experts - is this my problem and if so what can I do about it?

Next; is this a problem?

I don't see any witness marks on the stator, nor any issues with the wiring:

 

[rtcosic]

Turning next to my favourite grinder:

First is the initial on-off switch.
This I can remove and do a simple continuity test. I think I've done this before and it passed, but let's start at the very beginning to be sure. I'll go all the way back to the mains plug and check the wires too. All report backs will be tomorrow.

Next a series of photographs of the variable speed module and all the connections:

I'm a little embarrassed to admit the black, blue and red wires potted into the module have me confused and I'm not sure where to attach my direct power live and neutral.

Any suggestions?

 

[Kram]

Second pic is too blurred, is this section of copper eaten/burned/melted away?

The damage in the 4th pic is odd. The rotor has been ground/cut for balancing at the factory. I dont see how that has happened either before or afterwards.

 

[rtcosic]

Second pic is too blurred, is this section of copper eaten/burned/melted away?
View attachment 478521


The damage in the 4th pic is odd. The rotor has been ground/cut for balancing at the factory. I dont see how that has happened either before or afterwards.

I 'zoomed' in by cropping the original photograph. I'll disassemble again and use my Mk1 eyeballs to inspect more closely and report back - after supper.

That damage has me puzzled, but I'm easily confused on these matters. The insulation seems to be missing too.

 

[tigdlo]

Looks like the wire has melted/broken in 2 and exited out of the slot, the only part not worn away is where it's sitting in the balancing cuts. The inside of the stator is marked where its worn away the armature wire.

 

[angellonewolf]

Looks like the wire has melted/broken in 2 and exited out of the slot, the only part not worn away is where it's sitting in the balancing cuts. The inside of the stator is marked where its worn away the armature wire.

2nd what he said

looks like the copper windings either end and black in the middle poped come out and the rotation took care of the rest

 

[rtcosic]

Looks like the wire has melted/broken in 2 and exited out of the slot, the only part not worn away is where it's sitting in the balancing cuts. The inside of the stator is marked where its worn away the armature wire.

2nd what he said

looks like the copper windings either end and black in the middle poped come out and the rotation took care of the rest

Thank you - I was coming to that conclusion as I inspected the photograph. I hadn't noticed the missing insulation when I looked at it in the field, and I was looking for gouges in the stator, not smeared copper!

I shall deem this rotor to be beyond economical repair.

Trying to source a replacement without knowing the model number might be a challenge!