WM BMS250 cbn sharpener stopped working

[jimbarry]

Saturday of course, WM Canada is not open on. the weekends. Did a bunch of blades yesterday. And I did 4 blades this morning, not an issue. Put in another, it got about half way around and stopped advancing, motor for the cbn wheel still going. So I figured the blade might of had a bend in it whereby the electronics engaged to stop the cam from advancing. Blade appeared ok. So I shut the cbn motor off. Turned it back on and no go. Set the emergency stop switch, reengaged it, press to start the cbn motor and no go, no light on the button to indicate power. Open the control panel, see a red light on some sort of block (capacitor or fuse?).  Engage the emergency stop again, red light on block goes out. Reengage the emergency button, press the start button for the cbn motor, the button doesn't light up but the red light does come on that block and I can hear a single click noise at that same time.

There's one small fuse I can see, I think it reads as 1.6A and looks like its filled with crystals of some sort. Never seen a fuse like that, if its even a fuse.

Anyone have some insight?



 



Link to Facebook video I uploaded there showing the problem.

[Ianab]

That's fairly standard little electronics fuse, some are packed with some sort of "sand" to quench them and stop them exploding if they are shorted. They blow, but the exploding wire doesn't bust the glass and leave shards rattling around inside. 

Anyway you can check it with a multi-meter, or even an automotive continuity tested. It's should measure ~0 ohms across it. 

Generally fuses in modern electronics are there to cut power after something has failed already (stops things catching fire). It's unusual to find Only a blown fuse in electronic gear. 

[YellowHammer]

My guess is your resettable relay has tripped.  They control each function including advance.  It is a small rectangular block in a group when you open the panel door. It will have a little lever that you can flip to reset the breaker inside the relay.  Or you can override the breaker in the relay and set the little lever to the always on mode.  It forces the relay closed and should function the advance.
It's a pretty common fault.  

[jimbarry]

Yellowhammer, is that what these are (circled pink)?

There is a small lever on them it seems.



 

[Southside]

Yes, that's them, mine did the same thing one time. 

[jimbarry]

It's should measure ~0 ohms across it.

It does.

Yes, that's them, mine did the same thing one time.

I tried the levers, didn't make a difference.

[Southside]

Did you rotate them in both directions to make sure it resets? Sort of like a tripped breaker in your home. 

[YellowHammer]

If it's the relay, did you reset the breaker?  Is this the relay on the right?  The one that I marked with a Sharpie?  The little green lever is the breaker reset, it may be tripped, its hard to see when its tripped.  With the power off, pull the lever down to the full 6 o'clock position and then return it to the full 9 o'clock position.  It should click back into the 9 o'clock position.  That will reset the breaker in the relay and things should work.  

If you suspect the actual relay is bad, then pull the lever all the way down to the 6 o'clock position and it will lock, and leave it there.  That is the breaker bypass/relay contacts closed position.  It forces the relay into operating position as if the breaker wasn't tripped.  Turn the power back on and the machine will probably operate.  If so, then cut power, and return the relay lever to the 9 o'clock position and lock it into place.  That resets the breaker, and the machine will most likely work fine.  


  

Here's a description and picture of how to reset the breaker.  You'll probably have to expand the quote to see the picture. 

[jimbarry]

I tried what was outlined above. 

With the power on and the green lever at 6 o'clock, the cbn wheel motor and the oil pump will come one but the cam will not. Worth a note, none of the white lights come on the front panel.

Then I turned off the power, put the green lever to 9 o'clock, turn on the power and nothing works.

[gmmills]

     Apparently you have ruled out the relays. Sharpened many blades over the past few years on my BMS250 and never had a relay issue. There are 2 buss fuses on the circuit board. The fuse you have already removed and tested powers the high voltage circuit of the sharpener.  The issue you are having points directly to a blown fuse. This fuse is mounted on main board behind the separate removable pot board. The pot board needs to be carefully unplugged from main board to exposed the hidden fuse. This board is located just to the right of the relay, green lever, you have been trying to reset. This fuse is a 5 amp 20mm. It protects the low voltage side of sharpener circuits. This circuit only operates the power feed motor and shut off sensor.

[terrifictimbersllc]

On my BMS250  once, the clip holder for that fuse F2 wasn't squeezing the fuse tightly.

[YellowHammer]

Its does sound like the relay isn't the problem, with the behavior you are describing, the problem is more upstream of that, because it sounds like the relay isn't being triggered, which you can check with your voltmeter.  When you put it in the override mode, it forces the contacts closed, whether there is a trigger signal or not.  So if you get a voltmeter, you can check for the presence of trigger voltage and then follow the schematic upstream to find the fault.  So you are getting voltage through the relay but not the trigger voltage.

The hidden fuse is a pain to get to, but it should be checked.  After that, if thats not it, start going upstream.

[jimbarry]

I removed the 4 screws that hold the main circuit board in place. There is no fuse in behind it. I still don't have it working. I've been on the phone now with three different electrical engineers at Woodmizer USA. 

[jimbarry]

    ...This fuse is mounted on main board behind the separate removable pot board. The pot board needs to be carefully unplugged from main board to exposed the hidden fuse. This board is located just to the right of the relay, green lever, you have been trying to reset. This fuse is a 5 amp 20mm. It protects the low voltage side of sharpener circuits. This circuit only operates the power feed motor and shut off sensor.

I didn't see what you were saying earlier, but after getting Jason from WM USA on the phone today and being able to stand in front of the machine without dropping the call, we got this sorted out. It was indeed the 5A fuse in behind. A trip to town for a $2 fuse and we are back in business. Sure was tricky pulling off that small circuit board.
Thank you guys for your help and insight.
20201130 Woodmizer sharpener BMS25mu fuse replacement - YouTube

.... now who wants to help me put the undercarriage back together on my CAT 257B2 skid steer? ;) 

[YellowHammer]

That's great news. 

[gmmills]

 Glad you have it up and running. I have troubleshot many of these units over the years. That F2 fused circuit also energizes the relay trigger circuit.  Not hard to trace with my schematic.

  Now let us address the reason for the fuse failure. There are only 2 low voltage components on this circuit. The power feed motor and shut off proxy sensor. The most common reason for the fuse to fail intermittently is the power feed motor.  On older revisions of this sharpener had a Klauber branded motor on the power feed. The klauber motors are extremely durable. Wm has changed this motor to a Current Applications brand. The Current Applications motor is not as durable as a Klauber. The power feed motor failures I have been consulted on were all Current Application motors.      

[jimbarry]

There are some more funky things going on here. I managed to capture it on video a second time after it happening again yesterday.  You can jump to 0:55 in the video to see when it all starts.

20201202 Woodmizer BMS250MU electrical issue - YouTube

[terrifictimbersllc]

two thoughts....

if the blade is stopping at or near a particular position on it, like it seems you thought it would, then is it possible there is some deformation in the blade , (otherwise why would one position be different from another as far as the sharpener goes?), a deformation in the blade could bring it closer to the sensor at some points, I find occasionally a blade which will do that to an extent to shut off the machine.  the sensor is a metal detector not a magnet detector, the magnet is only so that chunk of metal sticks to the blade.  

flickering lights might have something to do with either the fuse being loose in its holder (this happened to me) or maybe  could it happen because there is just a little too close of approach of the blade to the sensor?

Maybe remove the sensor to see if it affects the flickering or stopping

your sharpener sounds different from mine, maybe its just because its a  recording, but it seems like there is extra noise during the pushing part of the cycle. Have you cleaned out the clamp body?

[jimbarry]

No deformations I could find. Its the first thing I look for. 

And yes, the machine does have an odd sound in the video, its not near as loud when standing in front of it.

[Stephen1]

I will follow along and hope you to see you get it running