Fitting new laser tube. High Voltage Tails - how to splice / join

I have an older (3 years now!) Blue Chinesium 50w laser. The laser power has slowly been decreasing to the point where my engraves are now only .2-.3mm deep, so I have purchased a new laser tube to keep it going for a while.

The issue is that it has come with 2 pre-wired tails on each end, but how can I safely join these to the existing wiring? I have some Wago connectors that are good for 32A 250V/4KV but after actually looking at the cable and seeing the amount of sheath around the small HV cable, I am worried that these are not going to be up to the job.

Can anyone advise the best thing for me to do?

They should be fine. You’re probably not going to exceed 25 ma and they will probably take more.

Good Luck :slight_smile:

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Thanks. I figured that they should be ok given the milliamps. Thanks for the luck. I may need it :smile:

UPDATE: All working. No arcing or anything to mention as of yet. This seems to have worked fine.

The sheathing is there because of the voltage involved. Starting (or strike) voltages required for ionization of a laser tube can be upwards of 50,000 volts. A lower power laser tube (like a 50w) may be more around 25KV starting (dropping off after starting to perhaps something down to 18 - 20KV).

Your connectors are only rated for 4KV.

You are correct about the voltage, however I sincerely doubt 32 amps… I made a poor assumption they came with the tube :frowning:

Ok, so the laser is out of action until I can get a solution - I am struggling finding any terminals that are marked up at anything near 25KV. Have you any suggestions here? Given that I have now cut the tails to suit the tube position, and spliced with the Wagos, I dont really have any choice but to splice, as my other option is to run new cable from PSU-tube at both ends - with the main issue there being that the red wire is directly soldered to the PSU.

Even the chinese ones they come with can go bad



But a quick search on ebay and $10 will get you a new set in a few days
CO2 Laser Power Supply Connector PSU Cable Connector / High Electricity Adapter

Yikes. After speaking to a few people - including a friend who works with HV in the sense of older machinery with CRTs and others, I have been advised to either get some couplings similar to above - or joint the cable myself (solder, dielectric/silicone, heat shrink, more heat shrink, even more heat shrink) and I feel a lot more comfortable with what needs to be done.

Having seen the above - I think I may go down the jointing it myself route.

On low current HV stuff like that I often solder & heatshrink or just use a plain old crimp connector and then slide a few inches of glass tubing over the joint and tape in in place so it can’t slide off. Glass is a very good insulator.

The HV connection to the tube on my OMT machine has a ceramic insulator that slides over the connection.

I had initially cleaned everything, realigned mirror etc, changed water etc all in an effort to find out why i could cut but engraving was a blurry mess so i guess a bad connection in that melted mess affected the low end of the setting. I am not really sure how arcing even got our of this connector, perhaps it loosened over the year and a half i have had it. But seeing the damage to it and t where it was arcing to and the distance i have much mire respect for this voltage. I had temporarily put some ceramic tiles over the connector to not allow the voltage to find a way out and that worked fine for a month then one of the tiles must have shifted and you know the rest. The new connector i had was from cloudray, arrived in a short time and all is good.i would not recommend doing your own joint unless you are very familiar with amazing how keen it is to arc when it finds even the tinyest opportunity

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I have gained a bit more respect for it than I had say at the beginning of the week, where I haphazardly used bog standard wago connectors… I have read, and learnt.

I have jointed it myself though. I can’t have a laser down. I’m just hoping a good solder joint and 5 layers of polyolefin shrink have done the trick.

I’m not really sure if there’s a way for me to test it other than using it and not dying in the process.

Regards

There’s many ways to insulate. Here is a link to 69 KV High Voltage Rubber Splicing Tape 1-1/2" X 30’ X 30 Mil I think it’s about 25 bucks a roll.

This is a soft putty that is Approx. 550 Volts/MIL Di-electric strength. Easy to work with but you’d need about 2" of it for a 30K dielectric.

The most simple is the first, which has the appearance of regular electrical tape, probably followed by a connector.

:slight_smile:

Voltage is also important, isn’t it?

I believe that most of these CO2 laser tubes are powered with 20kV or higher voltages and sufficient insulation is necessary to keep the wires from arcing to any nearby metal. McMaster-Carr sells the wire if you are in the US, though plenty of other places do, too.

Thunder Laser publishes this video on changing CO2 lasers in their machines and the OP may find that helpful. Not the heavy-walled connector between the two high voltage wires.

Yes, voltage is important but most of us don’t have the facilities to measure and/or monitor the hv supply. High voltages can be an issue, so most people deal with them the least, if that makes sense.

I have some resistors ordered specifically to measure HV and give me a connection for my scope so I can see the hv supplies performance. But generally the current is the best indicator of what power it’s lasing at… Plus it keeps you around ground level at the meter or cold end of the tube.

Mine is based on a 30kv, which should cover most hobby lasers anyway… Don’t take chances, use a good quality product and you should be fine.

I was referring to the insulation needed to safely connect two high voltage wires. Presuming that wire rated for the appropriate voltage (20 kV?) is used then one still must insulate the connection appropriately. The video I referenced shows the type of connector that I think is commonly used. I’m not sure where to buy properly designed and rated connectors of that type. A search on Amazon turns up several likely connector candidates, but none of the ones I checked say anything about the voltage rating nor who the certifying body might be. They could just be “cheap” Chinese imports of questionable quality. Or not.

I didn’t check any of the US electronic suppliers, like Digikey, Mouser, or Newark, but they might have something better than what Amazon offers.

Sounds like you have a lot more HV experience than I - can you suggest a quality source for the connectors? Sounds like something I should pick up before it is needed.

Millen and Alden make good quality connectors. And you pay for it.

The wire on these devices are usually supplied with the proper high voltage wiring. On these lasers most limit out about 30kv, but I’m sure that’s the hobby laser areas only. No telling about industrial levels.

I buy mine from Amazon or Ebay, a good mechanical connection, flowed with solder and gently assembled. The only places you need worry about are any breaks/holes in the wire insulation.

Good luck :slight_smile:

Thanks a great deal!