It just went blank-won't turn on

[DianMayfield]

Weirdness abounds.


Third carve of the day on my C machine. It is on it's own dedicated circuit. I was carving some centerline text as a test on some 1/4 in ply, the machine just quit, and the screen blanked out. There seemed to be an odd sound for about 30 seconds just before it quit, but centerline in not a smooth sound, could have nothing to do with it.

I unplugged it, and plugged it back in, screen is still dark. What the heck do I check?

Thanks in advance!

[bergerud]

That does not sound good. Could be the power supply. When the machine is on and you move the truck, is there any resistance? (Normally, when the machine is on, the servos get power and do not move as easily as when the power is off.) If the servos move easy, I think it is the power supply.

[fwharris]

Not to over look the obvious but did the circuit breaker trip?

[DianMayfield]

It may be a cascading event to the power supply, I didn't find a document that tells me how to determine if it is still good. I did remove the bottom of the machine (you can forget how heavy this beast is!) and found a capacitor that could be burned out.

I am all about root cause failure analysis. Off to the parts breakdown to figure out what this card is (a different card is marked power supply ) and if it could shut down the machine.

[bergerud]

That burnt board is the x termination board. The burnt circuit is part of the cut motor control. The cut motor would have quit. The the y motor should have then stalled. It should not have taken out the power supply but maybe it did.

You should try the servo resistance check.

[fwharris]

That is the X termination board.

[DianMayfield]

Floyd, good call on the circuit. It wasn't tripped, but my surge strip was... we have dirty, rural power here, so everything is on a strip. Machine now powers on again. Weird that it tripped from the machine out. Electricity, one of the great mysteries of life (and I work in power plants!)

Dan, I did a search of the forums and the, now badly organized, support docs. Didn't find anything on doing a servo resistance check. Would you have a link?

Thanks to both of you for calming the mild case of panic. Just knowing all of you are out there really helps when things go south :)

[bergerud]

Dan, I did a search of the forums and the, now badly organized, support docs. Didn't find anything on doing a servo resistance check. Would you have a link?



I think I made that one up. It is just one of those things one notices. When the power is on, the servos resist turning and so it is a check to see if the 24v is working.

So, what happened then. We need a debriefing. The x termination board fried, the cut motor stopped, the bit dragged overloading the x and y servos and tripped your surge breaker. Is that what you think?

[DianMayfield]

I think I made that one up.

Priceless! I do believe we should add it to the official vocabulary as it certainly makes sense. OK, this morning I ran the user tests. No-go on the cut motor test, all others successfully completed.

There are hundreds of x-termination board posts. This tells me that there is a problem with the board design. I have electronics that are 30+ years old that haven't blown capacitors. If it meant to be cheap protection to more sensitive parts, it shouldn't be over $60. Any thoughts as to what would cause that cap to fry? I would like to put preventative measures in place if there is a known culprit.

I will be putting the x-term board from the A machine I picked up in it to confirm the motor isn't damaged in some way as well. 254 cut hrs- say, there isn't a timer on the thing, is there? :)

[fwharris]

I think it is LHR policy now to request the customer to send in both the cut motor and X board when trying to trouble shoot problems in that area of the machine. It seems that they have determined that an issue in one causes a failure in the other.

Thanks for letting me know about my WAG on the breaker and good to hear that was part of it and that your problem is just the X board and not the controller.

[bergerud]

I am not sure what it is that is fried. The blue thing with the stripes is a resistor (the capacitor is the big red thing). The resistor could be fried. The board traces (copper conductors) near it look like they burned up. Too much current. This may indicate that there is something wrong with the cut motor. If the cut motor overheated and burnt the lacquer between the windings, it would draw more current and fry the x termination board. The fault here may not be with the x termination board.

[DianMayfield]

Is there a wiring diagram for the CW? Butch, who was out of town yesterday, wants to check voltage and resistance before we replace the board. Wouldn't want to fry another if there is a problem with the motor. He says that yes, the fried resistor could have allowed a current spike to the surge strip and tripped it.

The shellac on R2 also looks very dark. And yes, the traces at R3 are burnt along the path. There is no shellac on R1. I'll upload pictures of the underside of the board once we have it out. He wants to see if the side of R3 is blown out.

[bergerud]

No diagram that I know of. I made one once for the triac snubber circuit there on the x termination board when I was trying to understand why the motor jerks when you close the cover and why it was drilling the hole for some people at the board sensor touch. Who knows where that went!

[Digitalwoodshop]

My thoughts on the X Termination Board.... In the beginning.... No glue was put on the Capacitor and in the early years the QC Vibration would cause the body of the Cap to vibrate and the this copper wire would snap.

LHR has been putting a glue or lacquer on the C1 cap further protecting the cap from vibration. They also put it on the Resistors and that in my opinion is a poor idea... Resistors are designed to dissipate heat as they do the resistor thing... That is why a 100 ohm resistor comes in so many sizes... The bigger, the more heat it can dissipate. By covering the resistors they hold in the heat and burn the glue or lacquer causing the discoloration and even failure. I have never seen a resistor properly soldered to a board snap a lead... They just don't vibrate being pressed against the board and soldered in place.

The X Termination Board MAY be bad.. but possibly not.....

I would check the cut motor brushes and look for worn brushes... Remember the wire tether inside the spring of the brush can act as a dog leash and prevent the brush from reaching the copper while spinning and a arc will bridge the gap causing a strange noise in the cut motor prior to the machine going "tilt"...

AL

[DianMayfield]

A motor autopsy.... shorted across all windings. This is the same motor that had the loose loop in the wire connection, under the shielding last year. When you turned the rotor, there was a rub every 20% of turn or so. Will wait to buy x-termination board until we try it with the new motor. Hoping Al's WAG is a good one :)

[bergerud]

Not pretty. You could hook up another motor to test the x termination board. Just hook up your blender or any AC brush type motor and do the cut motor test.

[henry1]

Wow have to say like dan not good

[bergerud]

Besides feeling the flex for heat once in awhile, I also hold my hand on the top left of the machine cover to feel for cut motor heat. (This is where the cut motor cooling air is ducted.)

[Digitalwoodshop]

After seeing the motor.... My thoughts are to just trash the X Termination board... At the cost of Motors.... And seeing the damage... If the X is still functional it likely got very stressed and I would NOT ever use it again... Buy another....

The purpose of the X Termination board is 2 fold... 1st is to route the X Drive signals to the X Drive Motor and return the encoder pulses. The 2nd is to take the Computer Control Signals and through a interface of 2 optical couplers ISOLATE the Computer side from the 115 Volts AC Side.... The computer lights a LED light inside the opto coupler and a photo reciever on the other side of the chip will see the light and turn on.... It in turn turns on the Q1 Transistor or Triac that is the on and off switch for the cut motor... I have never fully understood the function of the 2nd opto coupler on the board... Someday #1 might take some time to enlighten us.... Inquiring Minds want to know.... Or is that with a E...


So I call them couplers... but they are really Isolators... https://en.wikipedia.org/wiki/Opto-isolator

Question? How long were the brushes? Any chance the Heating and Arcing of short brushes is what caused this? The "Plasma Arc" as the Carbon Brush tries to reach the spinning copper only to be held back by the dog leash tether...

[bergerud]

When you turned the rotor, there was a rub every 20% of turn or so.

How is it that the armature was rubbing on the field stator? Were the bearings gone? Did the casing melt?

[DianMayfield]

Can't resist.... When Al Speaks....

We all listen :)77449

(If you aren't old enough to get the reference, go drink some warm milk!)

Thank you Al, we really respect your opinion and will be ordering both in the AM. The brushes look good, there are only about 80 hrs on them. The one on the bottom is a new one.

I think that I will have one of our guys that worked at the Navy IMA shop take a shot at replacing the resistors. For a few bucks I may have a $60 part.. I am sure he would be upfront as to whether it would be a good idea.

Dan, Floyd and AL... you all rock!!!

[DianMayfield]

Dan,

It wasn't obvious what was rubbing. there was a little "grit" feeling to the bearings, but no wobble. The only evidence is the scuff marks near the "top" of the picture into the stator. It looked like some of the shellac may have been rubbing, I used a straight edge all around the rotor and nothing protruded.

[Digitalwoodshop]

OK... so it was not the brushes... Good job changing them 80 hours ago.

The copper wire within the motor is covered with a lacquer that acts as a insulator so the wire can be wound on itself. If for some reason that 2 wires rub it can cause the lacquer to wear off letting the wires short together. So something that started out as a 300 turn with a shorted set of wires could change it to an effective 150 turn coil. That would change the inductance and motor current. That would lead to smoke.... So just another WAG... Wild AL Guess....

Good Luck with the board rework.

A Growler would be used to test the motor parts.

https://en.wikipedia.org/wiki/Growler_(electrical_device)

https://www.youtube.com/watch?v=yXQ0heuV6VE

AL

[DianMayfield]

Been too much work lately .. just got to installing the new x termination board. The connectors do not fit in the mating sockets on the new board. My old board just had pins. Can I just pull the socket pieces off of the new board, leaving just the pins?????

[bergerud]

The old sockets came off with the plugs. I would take the old sockets off of the plugs.

You could, I suppose, take off the new sockets. Careful not to bend a pin and careful to get the plugs on the right way around.

[Digitalwoodshop]

The reason the old wire won't fit on the new board is that you pulled the pin guide off the old board... The pin guide is to stay on the old board... Remove it from the wire and the wire will fit the new board. The guide is designed to keep you from putting the wire on 180 degrees out....

:) good picture... helped see the problem.

AL


Darn... Old guy beat by a faster typist... :)

[lynnfrwd]

Many times the connectors come off the board with the cable. Take off the connector.

[bergerud]

Boy, there are some quick answers! (Kinda dumb to glue the plugs to the sockets when the sockets come off so easy. Hmm...)