Universal X660, L298 Driver Chips Blown Over and Over

[Destin Black]

Hi,
I have been reading this Forum for a long time, but I rarely post. I am an artist. I use my laser for other things as well, but its primary purpose is for my art. Most of the areas in which I have enough expertise to be helpful, don’t come up here. I hope you can forgive my lack of contribution and consider lending your assistance with a problem anyway.

I have a 50-Watt, Universal Laser X660. It ran fine for a while, then one day the X-axis motor stopped but the Y-axis motor kept going. The problem appeared to be a blown L298N driver chip. I did not feel comfortable replacing it. I can solder and de-solder, but not perfectly enough to work on something that cost thousands of collars to replace. I paid an associate to do it.

I ran the machine again. It cut for about an hour. Then the Y-axis motor went out. It was the same problem. It was weird, but chips die. It could have been a coincidence. I have lots of L298N chips. I use them for unrelated things. I had my friend replace the chip again. This time, I made sure to use a brand-new chip from a different source, just in case the problem was a bad chip. I ran the machine. It only went for about 10 minutes. This time the X-axis went out again. Three blown chips are not a coincidence.

I am comfortable doing mechanical work on the machine, but I really struggle with electric work. I did the best I could. I checked the output of the power supply. Everything seems to be as it should be. I don’t know what else could be wrong.

The man who replaced the driver chips for me is very good, but he is also somewhat slow, and his rates per/hour are very high. I don’t know if they are higher than normal, but they are higher than I can afford. I’d like to get a better idea of what could be wrong before I ask him to do anything else.

I have searched for useful information through the internet and the university academic database. The only thing I found that was similar was in an old post on this Forum. This is the link in case anyone remembers it.

https://sawmillcreek.org/showthread....d-big-problems







This is everything I know about the machine in case it is necessary:

I bought the machine a broker, from an auction company. Universal gave me the information they could before I bought the machine, and a bit more afterwards. I knew buying a used machine was a gamble, but the price was low enough that even with repairs it would be a good deal. It was also all I could afford. The machine has the second laser option, but only one is installed. There is no air assist. It has a 32 x 18’’ bed.

I felt comfortable dealing with mechanical repairs so the first thing I did with the machine was to take it apart, clean it, and put it back together. I replaced all the belts. I was told that this probably was not necessary, and the belts seem to be in good repair, but I did it anyway. It wasn’t that much extra trouble since I was already taking things apart to clean. I also replaced a small apart in the mechanism that lifts the bed. I noticed that the pulley that connects to the bottom of the one of the lead screws was touching the base of the machine and I knew that it should not. The problem was easy to see. The set screw that held things in place was stripped. It was an easy fix. I cleaned it again to be sure that it was pristine. Then I spent a good bit of time making sure it was perfectly aligned and calibrated. This was hard since I did not have all the correct tools, but I got it done. Then I called an engineer from my university and had him check and verify everything. He found no flaws. Once that was done, I had the laser cartridge recharged and replaced all the optics including the Beam window. Everything was old and obviously worn out, so this was necessary. I also added a 1.5’’ lens. I replaced the honeycomb material in the bed. The machine ran perfectly after that for some time.

I run the machine with the exhaust system that came with it. It is an older system that has been phased out, but the filters and cartridges are still available. I contacted the company that makes it. They were as helpful as they could be. They didn’t have all the technical information, but they gave me everything they could and helped me to get the system set up. The person I spoke to said that it sounded like the system was not big enough for the laser, but he could not be sure because of the changes that were made in later models. I see no indication that this is the case. I am supposed to be able to set it up to adjust the air flow, but we couldn’t find instructions to that, so I just run it on its highest setting. The smoke disappears almost instantly. It clears visibly faster than the similarly sized machine at my university. I think it is fine.

[Bill George]

Sounds like the power supply is perhaps putting out to high voltage or your motors or the axis are binding up in some way.

[Kev Williams]

What will blow out stepper drivers is any sort of compromised wire or connection. Been dealing with this nonsense with my Gravograph LS900 for months- Stems from my X stepper wearing out and a bad wire... the stepper works fine but screams like a banshee on the long runs as the bottom bearing is apparently lube-less due to a combination of how hot the motor is normally at rest, that I had one of the X motor wires in the drag chain break and short out, which caused the motor-to-machine plug to burn badly, all of which ended up frying the X driver in the controller. $300-something bucks to fix the X driver later everything was rosy but the stepper still screams. Ordered a new stepper, my rep brought it here, was totally different, would have worked for the Y but not the X as the thing didn't have enough grunt to stop the gantry at full speed without skipping upwards of 2" sometimes. Out it went, banshee went back in, another new one came in, it worked great for about 5 days, and while sitting idle for 20 minutes after working just fine all day, the X axis went dead, and there a hint of 'hot electric' smell- the stepper roasted one of its coils (is our guess) shorting the motor and leaving me with a 'motor over temp' error on the screen. According to the repair manual, the motor frying could've just as easily taken out the driver or the whole controller. So far I'm lucky the controller proper is okay- for now anyway... The banshee motor is back in, working great- why, I have no clue!

-- anyway, check all connections and wires-- it's a good idea to pull connector plugs and spray both ends with electronics cleaner. Check the wires in the drag-chain running vertically along the Y rail, I've had this machine and my Chinese Triumph have wires go bad within the chain, both within the area that the chain 'bends'. The Triumph had soldered wire connections, one of those connections broke, the LS900 had a green wire slowly get rubbed enough it wore the insulation off the wire, then one of the strands broke, and that one strand touched the machine frame...

[Destin Black]

What do you mean by "binding up." I dont think the motors are broken. I took the X Axis motor out and tested it. It seems fine as far as I can tell.

[Destin Black]

I inspected the wires for obvious wear and weak connections. I didn't see anything. If it is there, it is hidden. The Universal is set up differently from the glass tube type lasers Ive used. There are not any wires that move around much. The belts are all contained inside the tracks and gantry. The x-axis connects with something called a flex cable, which is just what it sounds like, a flat flexible cable similar to the ones you see attaching things like LCD screens in electronics. That was the very first thing the Universal Tech support guy had me check. There is no indication that its bad.

So far it sounds like my next step is to replace all the wires. I guess that is something I can do myslef. I think I can buy them all together from Universal so I dont have to construct them. The flex cable isnt terribly expensive so I could replace that too just in case. I really want to fix it this time. I hate to keep replacing the driver chips. Every time they are soldered and de-soldered I am nervous. Its also expensive. The guy I found to do it has pretty high rates. I am just too scared to do it myself. It would be my luck for that to be the day my soldering skills betray me.


I didnt try blowing air in the wire connections. That is a good idea. They look fine but there could be dust in them. I will try that to be sure next time I replace the driver chip.