MH-871-MK2 acting weird all of a sudden.

[cinikal 1]

Hello all! I woke up this morning to my cutter doing this.... Mh-871-mk2 It seems stuck but it seems like it wants to go. This unit has barely been used. Any help would be appreciated.

[Dakotagrafx 7,297]

5 hours ago, cinikal said:

Hello all! I woke up this morning to my cutter doing this.... Mh-871-mk2 It seems stuck but it seems like it wants to go. This unit has barely been used. Any help would be appreciated.

Did you ground the stand to the bottom of the plotter?  static build up in the roll discharging thru the plotter carriage is known to fry mainboards if you didn't do that as the documentation shows 

 

[cinikal 1]

No I did not as this unit sits on a bench. I really was not aware that it needed to be grounded as it was given to me last week from someone that retired. I sent a test print job  (a square, a circle, and a triangle) to it on Monday and was fine. Today I turned it on and this was the result. Is there a way to confirm mainboard?  Any tests with a meter I can do? Thank you for any help!

[Dakotagrafx 7,297]

If you upload your video using the attach files at the bottom of your dialog box so we can see the video without signing into Vimeo it would help.  I refuse to sign into anything provided in a  hyperlink for security reasons 

[MZ SKEETER 4,708]

2 minutes ago, Dakotagrafx said:

If you upload your video using the attach files at the bottom of your dialog box so we can see the video without signing into Vimeo it would help.  I refuse to sign into anything provided in a  hyperlink for security reasons 

Agreed 100%   I wouldn't sign up for Vimeo  either.  

[cinikal 1]

Sorry about that. Here it is.

[cinikal 1]

Here is another one just in case

[Dakotagrafx 7,297]

Impossible to say for sure but betting on the main board ,  the my series has had 3-4 different ones and important to get the right one 

[darcshadow 1,626]

Just so you're aware, the static issue, is static generated by the vinyl as it unrolls and feeds through the cutter. By grounding the stand you are providing a ground path for the vinyl. If the cutter is on a desk and the vinyl is just laying on the desk/ground you'll want to get one of the grounding kits. Basically it's a metal chain that hangs from the cutter and drags across the vinyl. Simple enough to rig up your own if you don't want to buy it.

[cinikal 1]

Thank you for the info. I have it on a grounded mat in a shop now. All our desks are grounded and tested yearly for ISO inspection. I will directly ground the unit to ground. I hope that should suffice?  Off to try to order a new mainboard.

By any chance does anyone know what gets shorted out? Could it be the drivers for the motors themselves? While I wait for the new board I will hook up my O-scope to see if I see any faults.

Thank you all for your input.

[darcshadow 1,626]

Just to be clear, the unit itself is grounded through the plug. The key is grounding the vinyl. People with a stand accomplish this by grounding the stand to the cutter. Since the vinyl sits on the stand the vinyl is also grounded.

Don't know about what get's shorted, but I would suspect the main micro controller would be the most susceptible, drivers/FETS are usually a bit more robust. 

[cinikal 1]

So I solved the issue. If anyone encounters this problem take a look at the power resistors that are right next to the driver chips marked A4975slbt. The resistors are marked R22 for a .22ohm value. The resistor gets blown and the result is this erratic movement in the video. Mine was in the y-axis section which is marked on the board. All I have at the shop at the moment is a .5 ohm 3 watt resistor but it is good enough to show that indeed the resistor was the failure.

[darcshadow 1,626]

Nice debugging, thanks for the info.

[slice&dice 2,450]

Wow. As many times as there's been this problem appearing, this is the first time an actual direct causation is shown. From static frying the sucker.

I am impressed that 'test' replacement resistor got it running, wondering if the thing just could be left in there, operating the cutter? It'll fry if another jolt hits, it, granted, but for now, it's Ok like that, right?