From smoking to crackling

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Doug Fisher
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Re: From smoking to crackling

Postby Doug Fisher » Tue Dec 27, 2016 8:33 pm

No doubt you have searched for all the arcing threads here but also do it at Sawmill Creek. There is good information there too that might give you troubleshooting ideas. I would definitely redo the connections at the tube just to rule that problem out. There are some decent videos about this on youtube. Russ also discusses it in one of his videos.
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fred ungewitter
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Re: From smoking to crackling

Postby fred ungewitter » Wed Dec 28, 2016 6:47 am

These later posts are encouraging indeed. I noticed some particulate matter on the motor housing under the tube. I figured it might be blown out acrylic dust or similar, as it wiped off easily enough. With the condensation from the cold water feed, I can see how there would be undesirable current paths.

I will locate the hints and tricks for rebuilding the connection. I agree that there is little to lose. It's not going to get worse than not-working, although it certainly might become not-sparking and that's being hopeful.
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Dustin Hawkinson
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Re: From smoking to crackling

Postby Dustin Hawkinson » Wed Dec 28, 2016 9:56 am

I'm a little late to the party, but I agree that your tube might still be serviceable. If you are seeing arcing, almost all of your power is shorting to ground and not being used to fire the tube. If you get that figured out, I bet your tube will fire again.

I don't think that the chinese manufacturers are using wire on the HV side that is rated to carry what we put through them. If you are doing all this work to fix the issue now, I would consider just replacing the HV wire completely or adding additional insulation and re-routing the wire to avoid passing near the frame as much as possible, adding rubber grommets where you need to pass through. If you upgrade the tube later and run it at higher power, you might have problems again if you just patch up one area.

To address something you asked in the beginning of your thread, what power % are you using to drive 18mA? It will be a higher % than if you remove the multimeter and its resistance, but it will still give you an idea. I'm guessing you are using ~60% - 70% which means you probably have plenty of power remaining to achieve 60A.
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fred ungewitter
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Re: From smoking to crackling

Postby fred ungewitter » Wed Dec 28, 2016 10:19 am

Dustin Hawkinson wrote:I'm a little late to the party, but I agree that your tube might still be serviceable. If you are seeing arcing, almost all of your power is shorting to ground and not being used to fire the tube. If you get that figured out, I bet your tube will fire again.


Grasping at anything resembling positive karma, I'm hoping your description is on the mark.

I don't think that the chinese manufacturers are using wire on the HV side that is rated to carry what we put through them. If you are doing all this work to fix the issue now, I would consider just replacing the HV wire completely or adding additional insulation and re-routing the wire to avoid passing near the frame as much as possible, adding rubber grommets where you need to pass through. If you upgrade the tube later and run it at higher power, you might have problems again if you just patch up one area.


I may have stashed away some number ten high-strand-count silicone insulated wire, which is about four times the cross section of the stuff that is in place now. If I can find it in my mess, that will be the first thing to get replaced. I've previously sent an inquiry to LO about their real 60w tube, currently out of stock. Expected stock date is late january. The person who responded also suggested to check the connection at the hv contact point.

To address something you asked in the beginning of your thread, what power % are you using to drive 18mA? It will be a higher % than if you remove the multimeter and its resistance, but it will still give you an idea. I'm guessing you are using ~60% - 70% which means you probably have plenty of power remaining to achieve 60A.


My research indicates that this tube should not be driven beyond 18 ma, as it's not truly a 60w laser. I was able to perform some cutting at the 55 percent level I tested to 18 ma, although the ammeter was then reading 17 ma. I think what you're suggesting is that at 55 percent and 18 ma, I have enough reserve power to get a true 60 watts (not amps) from a replacement, should it be a true 60w tube.
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Keith Sherwin
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Re: From smoking to crackling

Postby Keith Sherwin » Wed Dec 28, 2016 11:07 am

Fred, if there is moisture on the wire, then wipe the wire off with the alcohol. You do not require heavier gauge wire. What you POSSIBLY do require is better insulated wire. Moisture is or can be a big problem with high voltage.
You might want to make sure the interior of the tube area does not have high humidity by blowing a fan into the area or possibly use a heat gun on low heat, but be careful to warm the area GENTLY.
I remember from long ago the problems that were associated with too much humidity and high voltage arcing. Florida seemed to have the worst problems - along with the Toronto area.
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Ron Gosnell
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Re: From smoking to crackling

Postby Ron Gosnell » Wed Dec 28, 2016 11:15 am

That's a good point. I've seen posts about remaining under the dew point. A fan is a very good idea.
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Don Flynn
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Re: From smoking to crackling

Postby Don Flynn » Wed Dec 28, 2016 11:48 am

If you need a new tube check out Mactron on Alibaba that is where Russ got his tube. I purchased one from them recently there 60W is more like a 75W tube and it is built really well. It has performed exceptionally well right before mirror #1 at 21 mA its 71W and at 21mA i am getting 69.5W after mirror #3. I received it quickly from china via DHL to US ordered on Tuesday and had it Friday. Big downfall was shipping cost more than tube but in line with LO cost.
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Keith Sherwin
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Re: From smoking to crackling

Postby Keith Sherwin » Wed Dec 28, 2016 11:52 am

Don, Could you please post the link?
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Bill Wazny
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Re: From smoking to crackling

Postby Bill Wazny » Wed Dec 28, 2016 12:53 pm

one other suggestion would be to wrap the area of the tube with a good quality electrical tape. This MAY provide enough insulation to prevent further arcing. Your vendor will most likely request a video of the arcing after they tell you to remove the red wire and re-wrap it and re-insulate it . When I replaced my tube, I wrapped both connections with the Scotch tape pictured. It stretches as you apply it, and then it fuses into a solid silicone mass. It will not unwrap after a few hours. It must be cut off. It has an excellent insulating ability.
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Dustin Hawkinson
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Re: From smoking to crackling

Postby Dustin Hawkinson » Wed Dec 28, 2016 1:36 pm

Just to clarify on the wire thing, the higher the current (milliamps or amps) the larger the conductor needs to be and the more heat will be created. The higher the voltage is, the higher the ability to arc through poor conductors like air. Since we are talking about low current and very high voltage, insulation is of primary concern. Wire rated for high voltage has very good insulation.

On the other hand, there was some melted insulation mentioned. This could be caused by the conductor being too small (less likely) or by heat produced when the power is arcing through poor conductors like air, paint on the frame, moisture or minerals left by water on glass, etc (more likely).

I'm not trying to give you the solution, just a little background that might help you interpret the clues you find along the way.
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