Laser PSU shock

Electronics related to CNC

Laser PSU shock

Postby dwessels » Thu Sep 22, 2011 6:52 am

Well, got my first laser PSU shock. Not too terrible, but it is really annoying, loud and it makes you jump.

I had my laser and PSU test firing from the bench last week. Now I am ready to put it in the 2.x and it is not firing.
I have the 40w PSU that has the test button on it. When I hit the button, it makes a buzzing electrical noise, lights up 3 lights on it, but does not fire the tube. I am going to rewire the positive and negative connections on the laser and try it again.

This is what happened:
I unplugged it, pushed the test button several times and waited about 10 mins before disconnecting the positive screw connector (the big white one.) When I started unscrewing it, I got one of those 1 inch spark shocks.
I changed some wires, tested it again and then went through the same test / wait 15 mins, and it still hot. The second time I disconnected it with something insulating. The spark then jumped to the metal frame nearby.

Any ideas on how I can get rid of the charge on this thing so that I can work on it? I would rather not shock myself each time.

Thanks...
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Re: Laser PSU shock

Postby bdring » Thu Sep 22, 2011 11:10 am

My fan keeps running for a few seconds after power off. That appears to discharge it. The does not sound safe. Where did you get that supply?
Bart
"If you didn't build it, you will never own it."
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Re: Laser PSU shock

Postby BenJackson » Thu Sep 22, 2011 4:48 pm

I once fired mine with the big white connector disconnected (oops) and even after powering off and waiting I had a spark jump across the connector gap as I started to assemble it.

Capacitors can appear to self-charge after discharging due to dielectric absorbtion so you might not ever be able to safe these PSUs.
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Re: Laser PSU shock

Postby bdring » Thu Sep 22, 2011 4:54 pm

The high voltage capacitors I receive at my day job come with the terminals shorted to prevent self charging.

Most international standards require self discharging of equipment. I doubt these cheap supplies conform to any safety standards though.
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Re: Laser PSU shock

Postby dwessels » Thu Sep 22, 2011 7:39 pm

I got the supply from CNColetech.

I have sent them an email, but haven't heard anything back yet.
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Re: Laser PSU shock

Postby dwessels » Sat Sep 24, 2011 4:46 am

Figured out the problem. The HV connection to the laser pulled off of the post.
Everything seems to be working.

Thanks.
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