Before we Buy a new tube......

[Matthew Roach]

It sounds like the MA Meter will answer the question.

[Gene Uselman]

If you saw an arc... that is where the problem lies. Unplug the machine and wait an hour and then trace the High voltage wire to the tube, if it is arcing the tube is not getting the voltage. Check especially anywhere the wire passes thru metal bulkheads, etc. Sometimes the high voltage terminal on the tube is too close to metal,,, many possibilities- as Russ sez, these machines are basically kits assembled by semi competent and probably uninterested people.

[Matthew Roach]

Well, I installed the MA this morning. All I get is maybe 2MA on the pulse. I can't see anywhere that the red wire is arcing anywhere between the PS and the tube and I don't see any damaged wire. I did get a new wire with the ps that I did not use since there was a handy dandy connector that was the same on the existing wire.

[Gene Uselman]

The current of the pulse is controlled in the panel of the machine- there is a max and min laser % that can be set. If your % is set really low 2mA maybe OK. I am still concerned about the arc you saw- nothing should ever arc except a Van de Graaff generator when the science teacher walks by it after some industrious students plugged it in when he was out of the room. I know nothing...

[Matthew Roach]

So I actually got the arc to happen again it was the result of the handy dandy connector coming out of the power supply being too close to the power supply itself out it jumped back to the ground evidently on the power supply. When I get back to the shop Monday I'm going to try to run some programs at about 50% power and see how the ma meter reads then.

[Matthew Roach]

Ok, so this morning I ran a scan @ 50% power after it ran for a second with no reading on the MA meter. it started jumping ground from the PS connector to the metal case that goes to the tube like crazy. it seems obvious that for some reason the power is not going through the tube.

[Matthew Roach]

This is the offensive connection. But I wonder if this is just the symptom of a different problem that's causing it to arc here.

[Gene Uselman]

I think this is just a poorly routed HV wire [possibly poor quality wire as well] that is fairly common- we are talking thousands of volts here and the wire should not be close to any metal anywhere. I was thinking over the weekend- how well is your machine grounded? The Chicoms are kind of sloppy with grounds on a good day. The machine should be grounded to a reliable ground- not to your electrical system, I drilled a hole in the concrete floor and drove in a copper coated rod and ground to that- water pipes are good too.

[Matthew Roach]

I really appreciate your input Gene. It it does not have its own separate ground it is just grounded through the plug-in. So we will pursue that angle further since the milliamp meter doesn't seem to show it going through the tube. Thanks

[Jeffrey Aley]

There are a number of potentially deadly problems here that must be addressed ASAP.

First, regardless of the grounding of the machine or not, the HV wire should never arc to anything. If the connector is not rated to insulate the thousands of volts that it will normally carry, then you need to replace it. Ditto for the wire itself - you have to use wire with special high-voltage insulation (like spark plug wire). We are talking about thousands of volts, and enough current to kill you VERY dead. This isn't like messing with 120V AC house wiring. Hire an expert if necessary.

Second, regarding the grounding of the machine. The laser machine should be connected to a good earth ground. (I use the word "ground" here because I and the OP are both in the USA). If the ground on your electrical outlet is of high quality, then it should be sufficient. For example, if you're in a relatively modern shop with properly inspected wiring, you're probably okay. On the other hand if your shop is in a very old building, with questionable wiring installed by some guy who owned it in the 1950's, then you should be sure to install your own ground.

Finally, even if the plug is grounded, that does NOT mean the machine is grounded. A simple test is to unplug the machine and measure the resistance (with an ohm-meter) between the ground pin on the plug and a place on the frame. If it's less than 3 or 4 ohms, then you're fine. If it's higher, then you have a problem. On some machines, the ground wire is internally bolted to the frame (good). But they didn't remove the paint / powder coating before attaching it (bad). A little sandpaper will remove the powder coat so you get a good connection.

Regards,

-Jeff