Question about mA Meter on Chinese Laser (With Video)

[Matt McCoy]

You likely need a new power supply and tube. Lens, mirrors, and distilled water are not the remedy to your symptoms.

[Brian Leavitt]

mA meters don't lie. The tube is made of glass, glass is a insulator, unless the tube has a flaw or you have a bad ground connection it should never try to arc.

I think arcing is the wrong term. That's just what I've seen it called. My mA meter is "lying", though. Well not really, but I just found out today that I had purchased an AC mA meter and not a DC mA meter. Whoops...
DC meter is on order.

[Brian Leavitt]

You likely need a new power supply and tube. Lens, mirrors, and distilled water are not the remedy to your symptoms.

Switching to distilled water most definitely had a positive effect on the tube - noticeably more stable. The readings of my current mA meter are a moot point since I found that I accidentally got the wrong one. Other that that, poor cutting performance is the only real issue I had so new mirrors are going to help tremendously in that department. I'd put up a photo of the current mirrors, but I don't feel like taking it apart right now. There is no visible reflection off these things and they get quite hot after running the laser. I don't know how the beam was making it to the lens.

I'm aware that the tube and power supply are of similar quality to any other part of this machine, but at this time I don't think they are the problem. If I'm wrong, I already have a tube lined up for purchase. I've been trying to find an extension piece for the side of the laser cabinet, to cover the future 60W tube. So far no luck, but the search continues.

[Bert Kemp]

Call Rabbit in Ohio they might have an extension case they had one for mine. In any event should not be to hard to make one if need be, any sheet metal shop could do it.

Switching to distilled water most definitely had a positive effect on the tube - noticeably more stable. The readings of my current mA meter are a moot point since I found that I accidentally got the wrong one. Other that that, poor cutting performance is the only real issue I had so new mirrors are going to help tremendously in that department. I'd put up a photo of the current mirrors, but I don't feel like taking it apart right now. There is no visible reflection off these things and they get quite hot after running the laser. I don't know how the beam was making it to the lens.

I'm aware that the tube and power supply are of similar quality to any other part of this machine, but at this time I don't think they are the problem. If I'm wrong, I already have a tube lined up for purchase. I've been trying to find an extension piece for the side of the laser cabinet, to cover the future 60W tube. So far no luck, but the search continues.

[Dave Sheldrake]

Using a conductive coolant on a glass tube most certainly does affect power, to demonstrate this stick a 50/50 mix in your machine then fire it up, power will drop like a rock.

The latest 1050mm tubes are indeed 50 watt but are very low quality, a year is doing well, any more than that is amazing.

Make an extension on the machine but make sure to add a decent copper bonding strap that runs from the machine body down the inside of the extension. They don't need to be metal, they just need to have a path to earth

Mo mirrors are very good but they will corrode or tarnish so have to be kept clean on a daily basis

[Dave Sheldrake]

Using a conductive coolant on a glass tube most certainly does affect power, to demonstrate this stick a 50/50 mix in your machine then fire it up, power will drop like a rock.

The latest 1050mm tubes are indeed 50 watt but are very low quality, a year is doing well, any more than that is amazing.

Make an extension on the machine but make sure to add a decent copper bonding strap that runs from the machine body down the inside of the extension. They don't need to be metal, they just need to have a path to earth

Mo mirrors are very good but they will corrode or tarnish so have to be kept clean on a daily basis

[Brian Leavitt]

Call Rabbit in Ohio they might have an extension case they had one for mine. In any event should not be to hard to make one if need be, any sheet metal shop could do it.

Thanks for the tip. I'll give it a try.

[Brian Leavitt]

Using a conductive coolant on a glass tube most certainly does affect power, to demonstrate this stick a 50/50 mix in your machine then fire it up, power will drop like a rock.

The latest 1050mm tubes are indeed 50 watt but are very low quality, a year is doing well, any more than that is amazing.

Make an extension on the machine but make sure to add a decent copper bonding strap that runs from the machine body down the inside of the extension. They don't need to be metal, they just need to have a path to earth

Mo mirrors are very good but they will corrode or tarnish so have to be kept clean on a daily basis

I'm going to see how much time I can get out of this tube before it dies. It is a year and a half old now.

I thought about making an extension out of plexi. That is what I will probably do if I can't find a cheap one pre-made.

[Jerome Stanek]

you could have a sheet metal shop throw one together pretty quick. heating and cooling companies

[Kev Williams]

The latest 1050mm tubes are indeed 50 watt but are very low quality, a year is doing well, any more than that is amazing.

I just love(hate) the planned obsolescence build ethic these days: Build it to break down at 1.2x the warrantee period so we can sell replacements...

Not that this is new thing...

[Matt McCoy]

Switching to distilled water most definitely had a positive effect on the tube - noticeably more stable. The readings of my current mA meter are a moot point since I found that I accidentally got the wrong one. Other that that, poor cutting performance is the only real issue I had so new mirrors are going to help tremendously in that department. I'd put up a photo of the current mirrors, but I don't feel like taking it apart right now. There is no visible reflection off these things and they get quite hot after running the laser. I don't know how the beam was making it to the lens.

I'm aware that the tube and power supply are of similar quality to any other part of this machine, but at this time I don't think they are the problem. If I'm wrong, I already have a tube lined up for purchase. I've been trying to find an extension piece for the side of the laser cabinet, to cover the future 60W tube. So far no luck, but the search continues.

Using a conductive coolant on a glass tube most certainly does affect power, to demonstrate this stick a 50/50 mix in your machine then fire it up, power will drop like a rock.

The latest 1050mm tubes are indeed 50 watt but are very low quality, a year is doing well, any more than that is amazing.

Make an extension on the machine but make sure to add a decent copper bonding strap that runs from the machine body down the inside of the extension. They don't need to be metal, they just need to have a path to earth

Mo mirrors are very good but they will corrode or tarnish so have to be kept clean on a daily basis

Dave: Brian originally stated that his tube was squealing and did not have enough power to cut even 1/8" material. The meter he installed indicated that there was an issue as well. It looks like Brian installed the incorrect meter, which explains the goofy reading, but will distilled water address the squeal and poor cutting so dramatically. Brian?

Thanks.

[Bill George]

Its interesting that I ran RV anti freeze, then 50/50 automotive anti freeze and all with just tap water. No squealing and no reduction in power. Perhaps some sort of capacitor effect on the electrons inside the tube happening, but not conductive in a normal glass tube, not defective. Unless someone removed the ground from the tube or it was faulty, then the voltage inside might try to seek another path.

[Brian Leavitt]

Dave: Brian originally stated that his tube was squealing and did not have enough power to cut even 1/8" material. The meter he installed indicated that there was an issue as well. It looks like Brian installed the incorrect meter, which explains the goofy reading, but will distilled water address the squeal and poor cutting so dramatically. Brian?

Thanks.

The noise is still present at about 20% power and below. Above that it's silent. I'm sure the tube and/or power supply is not in tip top shape, but it fires and engraves OK. I haven't actually run anything on it since swapping coolants so I can't say whether performance has been affected. All I can attest to is that visually, the tube is more stable, and the noise it made at 29% power now only occurs at 20% or less. I just started taking everything apart in preparation for my new optics which should arrive Friday. Maybe I'll put it back together and make a test cut, if I have time.

What I find interesting is that by installing the wrong mA meter, I got some unintended information. It seems to me as though AC voltage is present at these lower power levels. It still registers about 3 or 4 mA at <20% power. This tube has always been useless at that power level and I only really run it at 50% power and up, so it never made much difference to me. I'm certainly not an electrical guru, so I don't know if there are other phenomena that would make an AC mA meter register like that.

[Brian Leavitt]

So I could previously cut through 1/8" plexi at 85% power and 6mm speed. Now I can cut through it at 85% power and 9mm speed. Same piece of plexiglass. I have done nothing since the first cut except for changing the cooling liquid.

[Bert Kemp]

So this would back the previous statements that the RV coolant robs some power and conducts some electricity.
By changing to distilled water the tube seem more stable (less arching) and you have a bit more power.

So I could previously cut through 1/8" plexi at 85% power and 6mm speed. Now I can cut through it at 85% power and 9mm speed. Same piece of plexiglass. I have done nothing since the first cut except for changing the cooling liquid.