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Mh721 Possible weak/intermittent carrier?

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Hello everyone, new user here. To start off this forum is great I’ve really learned a lot. Now to my issue:

The other day my cutter suddenly stopped cutting deep enough into the vinyl for me to weed. I thought this was odd. (Usual speed / pressure 150mms & 200g psi). So i upped the pressure to 400g, and no change. The cutter did not cut any better at 400g than it did at 200g. So for science i lowered specs to 100mms & 60g psi. And it cut perfectly, one time! After that no bueno. I called usc and they had me jump the carrier with a 9 volt, and i checked continuity from the carrier to the mobo, continuous. I believe my carrier is intermitten or weak so they sent me another. I will be updating once I receive it Tuesday. Also note, will be replacing my blade and cutting strip as well. Any comments, etc would be great, thanks. 

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Hey skeeter, i set blade depth by pulling it out of the machine and running it across the paper to the point where it didnt cut through the backing paper but still cut enough of the vinyl to make it easy to weed. I’ve probably cut roughly 15-20 thirty foot rolls of vinyl since i bought it a year ago. This will be my first blade change. Another weird thing that happened the other day that i feel is worth noting is that several times the carrier just dropped and would not go up, although it would still cut. I tried resetting a few times and this fixed the issue once. However i had the issue again (it wouldnt lift up) and i checked the carrier with a 9 volt and after it lifted a few times with the 9 volt it was up again. However, it still wont cut deep enough to weed it, no matter how far i ran the blade down or how high the pressure was increased. Does it sound like im messing something up though? I’ve never had this issue so the only thing i can think of is the carrier is intermittent.

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Very possible z chip problems. The zchip controls the up and down of the carriage head.  When you got your cutter did you ground the cutter to the stand, if you have one?  As you should have.  Static from vinyl fries a  zchip.  

This is how to set blade depth correctly.  Blades will wear down.  What you are calling carrier, is pretty confusing,  It is a carriage head that holds the blade holder..  (What we refer to as a  carrier is used under the vinyl to cut smaller scraps. Or contour cutting smaller designs. It has an adhesive finish on it to hold the vinyl)  If your cutting strip is gouged with bad places, then you either have your blade out too far or your not keeping the carriage head inside the vinyl and it is running off and cutting into your cutting strip.  

To start with, you should set your blade depth correctly, by taking the blade holder out of the machine, and firmly cut across a piece of scrap vinyl, you will be cutting. You should only be cutting the vinyl and barely a mark on wax paper backing, Adjust blade to get there, Then put the blade holder back in machine, and use the force of the machine to get there, same results, only cutting the vinyl and barely a mark in wax paper backing. You should just barely see and feel the blade tip out of the blade holder. 
 

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Hmmm okay thanks skeeter. Do the new mh models still have the z chips? I read those were a problem but all the posts I found were from really early like 2011. I checked my motherboard (mines on the side of the cutter i believe) but i couldnt spot any chip that looked like the z chip. I read the mh models have been through a few re vamps since then

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I don't own that cutter.  Also make sure the white wheels from the carriage head are firmly down in the track.  That will throw your carriage head off.  Check the arm that holds the blade holder.  They can crack from too much tightening down. 

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Ahhh. Yess i’ve checked all 4 wheels and went over my carrier arm thoroughly - no sign of damage. But your mentioning of the z chip has me wondering if that might be the issue again. Unfortunately my new carrier wont be here until Tuesday :( But I think i will give usc another call tomorrow am and ask them if the z chip is an issue for the newer models (mines a 2017). 

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put    

volt battery test                 in the upper right search bar.  for the whole forum and scroll down  

I can't offer any more help. 

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what they mean in your model doesn't have the z-chip in a socket that is replaceable . . . .like the old models - 

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depending on your soldering skills the z-chip can still be replaced, just not as easily as it use to be.

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would you think the z chip being bad in my mk model is more likely than the carrier itself being bad? Debating whether or not to give usc a call and go ahead and order a z chip a while. Just tryna get this thing fixed so i can get back to business really lol

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If your really depending on a cutter for your business, jump up to a better cutter. We tell people to stay away from this cutter. Too many problems with them.   Anything  above this cutter is better.  If you can afford it,  get the new Sc or Laser 3 now.  Or even higher to a servo cutter.  If you want to keep throwing money in this Refine, then that is your choice. The older MH cutters were better than these newer ones. 

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Its not my main occupation just a little side business I do, was hoping to be able to fix this one and use it for at least a little while longer. I'm definitely not against upgrading though. I just got home and ran a few more test cuts to get a better visual of what its doing, and I can definitely confirm the carrier is not putting pressure down onto the vinyl. I ran a test at 40g and a test at the max 600g. Both made the exact same cuts, no pressure difference. I know USC said a dull blade and tore up cutting strip can produce uneven results but even if the blade was super dull and the strip gouged, i would notice the pressure being put on the vinyl. I can confirm that the speed does change, i ran a test at 40mm/s and then at 600mm/s and the speed change is definitely noticeable. This makes me think the mobo is still good b/c its changing speed fine. I'm thinking the electromagnet inside the carrier is weak and isn't able to put pressure onto the vinyl. From my understanding the mobo energizes it up and down to put pressure on the vinyl. Sucks i'm on the east coast and have to wait a lil longer since the part came from WA.

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The more i think about it...if this carrier doesnt fix the issue I will probably just upgrade to that SC2 model. No point in dumping money into a cutter that will just break more often. Especially if the SC’s are more reliable! 

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Little update, installed the new carrier along with a new blade. No change. Now the carrier does not even drop when i turn it off. It just stays up. But if i push it down manually with my finger, it will cut with it down. So i'm guessing the z chip that controls it is toast. Or maybe its something deeper idk. Debating whether i should just get the SC2 or keep dumping money in this hunk of junk

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after some deliberation, and due to USC not getting any MH motherboards back in stock until mid-late june, I've decided to go ahead and pull the trigger on an SC2. Will probably still buy a motherboard for my mh721 & either keep it as a back up or sell it to recoup some money.

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If the cutter doesn't drop when power is turned off I don't think that's an electronics problem. With power removed there should be nothing holding the cut head up and it should just fall. The only two reasons I can think of that would prevent that, would be something physically blocking the head from moving, or power is not actually being removed from the solenoid.

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