Unbelievable K40 power supply earth grounding

[zendesigner]

I started an upgrade to the ramps for my K40 and was baffled by the way the PSU is connected to the Laser tube.

I'm sure i'm violating a dozen of european safety rules here :-)

So the PSU only outputs 1 Big red wire to the laser tube. 

It then exits the tube with the blue wire that goes straight to the AMP meter. 
Which for me is strange cause i always assumed you measure Amperage paralell to a device, and not inline with the device ????

And then the amp meter just connects to the GROUNDING WIRE ???? What the F***!!!

so i'm sending some thousands of volts throughout my grounding wires and if there should be a problem, through the case of the laser? 

I'm sure this should return back to the power grid wires.  this is higly irregular in europe cabling. 

How should this be fixed ? there is no return feed on the PSU ? 

Some pics

[Chad Davis]

That looks just like the one I just got. There is a grounding screw on the back of the machine case. The installation instructions in the manual that came with mine has you connect it to an earth grounding rod. If that is done there is very little chance the high voltage is going to take a path through you. 

[ajf]

The wiring is correct.  You're not sending any power into the grid, just grounding the device.  Remember that the PSU is outputting DC.

What you do want to check is that all the connections are sound, especially grounds. 

The grounding screw on the back is tied to ground on the mains input.  Think the Chinese tell you to wire it to earth ground because over there they often don't have ground on the mains.  The real purpose of the grounding screw is to ground the work surface the machine is sitting on if it's metal/conductive.  

regards,

aj

[zendesigner]

Hi Guys, 

thanks for the input. 

I think the problem i see is only in the Way that European regulations says that we have to do things here.  So i was kinda baffled by the way this is setup. 

I'm from Belgium and here not any device is allowed to return power over the Earth grounding wire, but needs to return over the "neutral' AC wire.  The reason for this is that every home needs to be protected by a differential security switch that cuts the power when it measures a difference between the positive Ac and Neutral AC wire. If power leaks in any other way to the ground, for example when you touch a live wire, the differential breaker cuts power in milliseconds. 

So for me this is a higly unusual setup. For Me the lasertube should connect back to the PSU and the PSU AC Neutral connection should never be connected to the ground meaning the chassis. 

Unfortunatly this is the case and built in with this PSU. 

It works of course, as long as my differential doesn't trip, but its not the best solution. 

It Actually means that if you lose your ground wire, and you touch the case, you will be the conductor and power will run between the laser and the ground through yourself.   Not the best security setup. But hey it's asian for some reason :-)

Zen

[irresistiblecam]

I want join to this discussion and not open a new one because I notice the same bad connections to my new k40, but it doesn't work.

I am desperate. My new K40 doesn't work. No laser fire and NO ammeter movement, the gantry works ok.

I think that it may be the power supply, so I replace it with new one, but nothing.

When I power it on, the fan on the back the machine start to spin, the red led on power supply is always on, and if If I push the test microswitch on power supply board, nothing happen. I checked the wire connection, and 220V from A an C is connected by the red wire to the pin 3 and 4. I let free the Ground wire Joint (D), just because it is internal connected to Groun pin (B) that is connected to pin 2. The pin 1 is connected to ammeter (inline) and than continue to laser tube negative. Between the pin 1 and pin 2 there is 1 ohm resistance.

Instead the positive laser tube (red cable) is connected to power supply internally without a plug. How could I test if on the tube arrive the correct voltage/current? I am prepared to buy some test tools to measure high voltage or to check the co2 tube. What is good for K40?

Please help me!

[ajf]

This video might be helpful: https://www.youtube.com/watch?v=dz4ln4_vT3g

Sounds to me like the tube is bad (i.e. gas has escaped).  Getting a meter that can handle will cost $3K+ I think, but there may be probes that plug in to a regular multimeter that might work which would cost $100-200.  You could test the PSU as noted in the video above with a big wirewound resistor like this one, much cheaper than getting a meter/probe.

I would also contact the seller and tell them it's still not working and, if they won't work with you to get it fixed, file a dispute with eBay/Aliexpress or wherever you bought the machine.

regards,

aj

[irresistiblecam]

I already finish the dispute with ebay/paypal. The seller sent me another power supply, because I suppose that it was broken. But nothing happens.  Now I got the money back by paypal, and I don't need to come back the machine.

If the co2 was escaped,  should I  see a red line into the tube, as you can see in the video, and also the ammeter must measure some mA?

at time 2:40 of the video I see that he short circuit 2 pin of data plug, what are the pin on my power supply? I need to short circuit them to test the power supply?

https://youtu.be/dz4ln4_vT3g?t=159

The ammeter on the control panel is inline on the ground wire, could I use my tester in parallel to measure the Ampere, how I must connect it right?

maybe to negative (yellow) and positive (red) wire to tube?

Thank you for reply

[ajf]

Well, it's good that you got your money back, got to keep the machine and got the second PSU.  

DO NOT try to measure the current in parallel! In fact, stay away from the red wire as much as possible unless you really know what you are doing.

I'm not what pins they are shorting and how to match them to your PSU, don't have enough information on either PSU.  However, it looks like they are disconnecting the control board and using the jumper to set the intensity to 100%.  You could achieve the same thing on a K40 by just disconnecting the control board and using the potentiometer and test fire button (the one on the panel) to do the test.

I don't think that a tube where the CO2 mix had completely escaped and was replaced with air (or worse water) would glow at all, I could be wrong though.  

I found this video and little write up about doing some testing with a homemade voltage probe. I don't recommend doing that! But it's interesting.

Before you do anything, are you sure that all your interrupts are functional and closed when you are testing? 

[irresistiblecam]

> Before you do anything, are you sure that all your interrupts are functional and closed when you are testing?

I tested all switch and cable.

What about the strange connection explained by zendesigner?

It is very strange that the negative tube wire is connected to ground and not to 220V or power supply negative DC

[ajf]

There is nothing strange about tying the cathode to ground in a DC circuit, especially a high voltage one like this.  If you look at any other similar laser PSU (or anything using similar flyback transformer - like CRTs) they are all wired the same. 

Tell us more about your PSU - link, manufacture/model number, or even just more pictures and maybe we can come up with more ideas.  I'm still thinking it's a bad tube given that you've tried two PSUs and confirmed that the interlocks are functional and closed during testing.

[zendesigner]

Hi,, 

It is indeed not strange for most of asia to connect PSU return to the casing and to the earht wire... It just ain't according to european specs.  

But it's built into the PSU , so i just accepted it. =-)

[John Dickinson]

It absolutely is within the EU rules to do it this way. You are misunderstanding the way things are.

Lots and lots of consumer and industrial devices do it this way. If you do not like it to be like that you can float the power supply but you will end up with a much more dangerous device if you do that.