Power loss after arcing

[John Noell]

For some reason (condensation???) out of nowhere my high voltage started arcing. It hit the tube and the case. No obvious damage. The connector seemed like maybe the crimp was a bit loose, so I cut it off and (lacking that one size of crimp-on, which is not to be found on this island) tightly wrapped the wire around the screw until I can get a new high-voltage wire 9with proper connector. Now, however, I seem to have lost a LOT of power and the engraving looks bad. Anyone have an idea if the tube or power supply (or both) is the likely culprit? And it could be that the connection between wire and screw is not as good as it needs to be, but I really tightened it after treating screw and wire with DeOxit (contact cleaner).

At least for now there isn't any more arcing.

[Ray Scott]

I take it that the loose wire was the RED wire going to the ANODE end of the laser tube. Did you put the clear-acrylic cap back over the end of the Reci tube? This cap acts as additional insulation and helps to prevent the arcing to the frame.

I have installed hundreds of Reci tubes on lasers... I hate the crimp connector. I normally cut it off and wrap the wire around the screw. The next step is to put some vinyl electrical tape around wire to act as a strain relief. (Tape the wire to the glass tube at the neck ...adjacent to the metal connect for). This prevents the wire from breaking loose again. ... Then put the clear acrylic cap back over the anode.

what came first? ... Tube or the power supply? Possible issues.
1) the tube has lost pressure. This causes an increase in the resistance inside the laser tube. The shorter route of least resistance was to jump to the laser machine frame... A jump to the frame could have damaged the motion controller. Hope that didn't happen. With a spark to the frame, the laser power supply transformer coils can be effected. Some of the windings become part of the sacrificial load... If the windings are damaged, then the laser power supply will start to have a crackling noise or louder buzzing noise. The AC whine is normal. .... Both the tube and power supply should be tested.

2) the tube was fine... The wire came loose? Added resistance outside the tube caused path#1 to be less favorable to jumping an arc directly to the frame. Transformers coil windings are damaged... Test the power supply and tube.

3) The tube was fine... The wire came loose? Added resistance outside the tube caused path#1 to be less favorable to jumping an arc directly to the frame. Power supply transistors are damaged from high power usage and overheating?

test the power supply first. buy an analog power meter from ebay. They are 0-50mA scale and only cost a few dollars. Buy a power resistor. Need a 100,000 ohm unit that can handle 100 watts.

How to connect the test parts?
(Power supply red wire)---------[power resistor]---------{analog meter}-------(return-voltage to power supply... Ground)

You would be looking for the analog amp meter to show near 29mA at full power output.
image.jpg This meter is only a few dollars.
image.jpg This resistor is nearly 6 inches long.


Test at the power supply. If it is good, then test the laser tube with the tube in place of the resistor.. Again, you should see the same amperage on the meter. If the amperage is significantly lower... The tube is bad.

thank You,

[John Noell]

Ray, WOW, thank you!!! Very helpful. The odd thing is that the (red) wire did not come loose and the acrylic cap was still firmly and fully in place. There is char from where the connector (still quite firmly screwed down) is attached to the tube and along the wire for about 100mm/4" to where it comes close to the metal box that sticks out from the case and covers the anode end. The inside of the connector along the wire was quite charred. The laser is in a room that has no air conditioning and the day was quite warm and humid. I have not noticed any condensation on the tube, but that end of the tube is hard to see when the metal box is bolted on to cover that end of the tube. Other than condensation I cannot figure out how the path of the arcing could have happened. I think it is just the tube as I do not hear any unusual noises from the PSU and it looks good (i.e., no obvious burns).

I will order a meter and resistor for testing as you suggest. Unfortunately, it usually takes about a month to get things mailed here.

PS I see two resistors on ebay that seem to match the specs but one is $79 (Clarostat VK100N) and the other (Ohmite Vitreous Enameled) is $12.50. Would either of them do?

[Bill George]

As long as the total resistance is the same and the wattage is the same I would think they would work. I am not Ray but I have been in the electrical and Ham radio field since 1962. Make sure you wire them as Ray as diagramed, the resistor first off the red + wire then the meter then the negative wire.
Once high voltage as arced over to ground it leaves a small carbon trail it will follow again. You could of had moisture or dirt that was damp start the whole process.

I would plan on replacing that HV wire. I don't know why copper wire core automotive spark plug wire can't be used.
PS If you are trying to use that old wire, forget it. That's your power loss right there, get a new HV wire on and try before you do anything else.

[John Noell]

I have ordered a new HV wire, but for now, I cut the end off to where it looks nice and clean, then stripped just enough to wrap around the screw. Since the tube appears to be bad, I figure I might as well wait until I get a new tube and new HV wire before doing much more.

[John Noell]

RECI asked for a video showing details of the tube and the tube (from end to end) while firing. After looking at it, they said they will give me a new tube for free. (That does not include free shipping of course.) Seems the arcing probably came after something in the tube failed. Wish I knew more about it.

[Rich Harman]

After looking at it, they said they will give me a new tube for free. (That does not include free shipping of course.)

I had a tube fail under warranty, RECI replaced it for free, including shipping via DHL, didn't cost me a cent. I originally purchased it direct from Reci, maybe that is the difference.

[Bill George]

Hope the power supply is still good.

[John Noell]

I had a tube fail under warranty, RECI replaced it for free, including shipping via DHL, didn't cost me a cent. I originally purchased it direct from Reci, maybe that is the difference.

I just found out they will do the same for me! Free shipping!