Laser won't fire-advice on troubleshooting needed

[daniel coyle]

alright, i describe in detail the demise of my weike by fire in a thread a few weeks ago. to get going again as fast as I can I was able to find a guy selling a slightly smaller and less powerful chinese laser that he said he never had hooked up. It is a YH 9060 by Laser World http://www.laserworld.com.cn/English/100.html
I want to upgrade the tube from 60 to 100 watts (I know that I will need new cradles and a new power supply for this - anyone who has any good US suppliers they can recommend would be helpful as shipping from china for these things... well, i don't know how much it will add to the cost.)
Anyway, I am trying to prove to myself that this machine works before I buy this stuff. It took me a bit to get it hooked up to 220 due to the chinese plugs. And it still is a little rough/primitive. When I turn it on without the water chiller attached it gives a continuous alarm. The alarm goes away when I attach and run my CW 5000. However, there is a profound leak at the end of the tube revealing a crack that I believe is confined to the water conveyance only. I believe the gas part of the tube is ok. Check out the pics and see for yourself
IMG_20130627_195825.jpgIMG_20130627_195858.jpg
So, not awesome. But I have researched ways to repair the crack and feel optimistic that I can make it watertight with silicone or epoxy.
Nonetheless, i wanted to make sure the laser does actually work and so tried to do some pulse tests with it (to avoid it being able to heat up without the water supply available.) well, no laser when I hit the button that I understand should generate one manually. so, i attach the chiller and route the water directly back into the chiller from the chiller's output valve. The alarm turns off and so the machine seems to think it is hooked up to a working chiller. again, i can't get a laser out of it. so, i check the power supply. there is 240 volts at the input to the supply. at the laser tube there is 31 volts whether i am pushing the laser button or not. any ideas?

dan

[George M. Perzel]

Hey Man;
Be very carefull-not sure where you measured 31 volts at tube but there shouyld be very high voltage at tube when operating-not measureable using normal meters. Sounds like bad power supply but sounds like you may have a number of issues.
Good Luck- BE CAREFULL AROUND HIGH VOLTAGE
Best Regards,
George
Laserarts

[Dave Sheldrake]

Something is leaking Dan (electrically not water wise)

You shouldn't get 31 volts anywhere on a laser, the PSU has a 12V rail, a 5V rail and the HV side that should give around 26Kv @ circa 16 to 20 Ma.

When I turn it on without the water chiller attached it gives a continuous alarm.

Some machines have a 3 pin water alarm wire that is connected to the chiller, if it's not attached you will get an alarm on startup.

As I said before though Dan, that crack is in the HV connection end of the tube, 20Kv and water don't mix and while not likely to be instantly fatal It's low amps) that sort of voltage can cause cardiac arrhythmia leading to the same end result. Chinese PSU's are well know to have poor or no current limiters, a dead short could easily provide far more than the 20 - 30Ma the psu will normally give out.

best wishes

Dave

[daniel coyle]

Thanks to both of you. Very difficult figuring things out. I want to be careful of course AND want to make sure I am not missing something obvious and amateurish in my troubleshooting before spending money I don't have to spend. Do you guys know what sort of voltage should be coming OUT of the Power supply when the machine is running but the laser is not being activated, and what sort of voltage should be coming OUT of the Power Supply when the laser is activated. After having a fire I am in no rush to have another problem and not in good shape to throw money away either.

[daniel coyle]

I guess what I am asking at this point is if there is a way to diagnose the Power Supply? Safely. And is there anyone in the states who sells parts for a machine like this? Shipping from china will cost me as much as the power supply.

[Dave Sheldrake]

In theory yes, the HV end can be measured but NOT with anything other than a properly designed ballast and specialist equipment. You can measure the BLACK wire end with an ammeter for current but not voltage.

On the HV end the voltage should read 0 (ZERO) when the tube is not powered (firing) but again connecting a voltmeter is going to end badly.

Looking at the damage to the tube the cause of no fire (beam) is more likely to be a damaged tube rather than the PSU, it is possible a knackered tube has killed the PSU but a hard thing to test without having swap out parts available.

There are other issues that can crop up, failed door switches, failed water flow meter switch that will all cause the tube not to fire.

Have a word with John at Hurricane Lasers or Ray Scott at Rabbit, both are in the US and may be able to help with a PSU.

For safety sake I'd rather not go in to too much detail about testing PSU's as the end results if you make a mistake can be fatal. Cascading problems are always the worst, you never end up knowing which or what part is faulty. Some PSU's have a test circuit but to be honest given the overall apparent issues with the tube at the very least I'd be dubious about trying it.

Honestly my friend, you really need to ditch that tube, I understand it's a couple of hundred bucks of trouble but 20 thousand volts near a leaking water supply isn't good in any way. I blew a tube when fitting a new 80 watt, turned round in the shop and forgot the thing is 5 feet long and smashed the end on a door frame. A few colourful words and kicking the drinks cooler made me feel better but I ended up just having to suck it up and try not to make the same mistake again.

Looking at in in a cold way, is your life worth $250?

best wishes

Dave

[daniel coyle]

Dave

Thanks for the reply. Really appreciated. So, I am ok with moving on from trying to make this tube work. I found out that I was not made aware that the tube is, while unused, at least 3 years old, so it could be dead from the shelf life or the crack or ...? I would still like to know if the PSU works and I do have a couple 100 Watt Reci tubes that I could connect to it. Is that a reasonable way to determine if the PSU works? Also, there is an ammeter on the PSU. Is there anything I can do by paying attention to the ammeter?
I have tried to contact John (couple days back by email) at Hurricane but no response yet.
Any thoughts on putting the 100 W tube in just to test the PSU?

[daniel coyle]

Well, the rep at Laser World got back to me and this is what she said about how to test the power supply

The method of testing the laser tube is well or not:
Make the positive and negative wire of the laser tube together

and then let the machine work, if the laser amperemeter of the power source box
show more than 20, and then the power source will be OK.

Sounds like I am supposed to contact the neg and pos wires and then pulse the laser button. Is this safe?

[Dave Sheldrake]

NO


I'm just off to the Docs Dan but I'll post back in a while, DONT connect the wires together.

[walter hofmann]

don't do this you destroy your power supply.
just connect a tube like it should be and fire a test with the test button from the laser power supply.
greetings
waltfl

[daniel coyle]

Thanks Dave, Walter. Will pulse the tube as you said, Walter, and see what the ammeter reads. Will let you know.

[Alexa Ristow]

Looking closely at the pictures, it seems as if there is water between the inner and outer sleeve. If this is the case , then is it not likely that the tube would have totally de gassed. Once degassed, the tube would no way of creating an electrical circuit between the two poles at all. Even if you do fire the tube, the Ammeter will still register an open circuit (0Ma). I think that the safest route would be to replace the tube in any case. this will eliminate one variable and allow you to test the power supply by pulsing the tube. A normal household or hobby level multimeter is dangerous when in the hands of someone who is not versed in High Tension electrical systems. Death kind of gets in the way of laser projects.

[Dave Sheldrake]

Sorry I had to shoot off Dan

Connecting a tube will show if the PSU is faulty OR if the tube is faulty or possibly both. A faulty tube will cause no power to flow through but could result in an arc to earth if the PSU is fine. Using the PSU test button (if it has one) will rule out a faulty flow sensor or door switch, it won't rule out a faulty tube or PSU.

To test the PSU alone you need a ballast to fire the PSU into while measuring the return amperage.

To be blunt, anybody who tells you to dead short a PSU is an idiot plain and simple. You could blow the PSU at best or damage the ground circuit and kill yourself if the PSU isn't current limited.

When doing the test with the PSU test switch, make sure the tube is fitted into the properly grounded machine as a faulty tube will result in an arc to earth / ground by the path of least resistance, if that path is you then it's not going to end well.

best wishes

Dave

PS: Hiya Walt (Exsecratio from the Zone)

[daniel coyle]

Sorry I had to shoot off Dan

Connecting a tube will show if the PSU is faulty OR if the tube is faulty or possibly both. A faulty tube will cause no power to flow through but could result in an arc to earth if the PSU is fine. Using the PSU test button (if it has one) will rule out a faulty flow sensor or door switch, it won't rule out a faulty tube or PSU.

To test the PSU alone you need a ballast to fire the PSU into while measuring the return amperage.

To be blunt, anybody who tells you to dead short a PSU is an idiot plain and simple. You could blow the PSU at best or damage the ground circuit and kill yourself if the PSU isn't current limited.

When doing the test with the PSU test switch, make sure the tube is fitted into the properly grounded machine as a faulty tube will result in an arc to earth / ground by the path of least resistance, if that path is you then it's not going to end well.

best wishes

Thanks again. Cherry on top of all this is that my bike got stolen from my fenced in yard today!

So, I still cannot get anything to register when I hit the laser button. The tube, as was said, might be old and lack gas for conduction. Would this prevent the ammeter from seeing current flowing out of the power supply when the laser button was pressed? I replaced the tube with the old tube from my last machine. This tube survived a fire without cracking or any apparent damage (I have no way of knowing if it is still good other than visual inspection.) the plastic cradles it was on got hot enough to melt away halfway. This tube did not inspire a response in the PSU's ammeter either. I am wondering now if it is the PSU or the signal to the PSU or what else could it be? It doesn't really make sense that the PSU is broke. IT was never used. I feel like I am maybe making some huge amateurish mistake and pressing the wrong button or just misunderstanding the chinglish directions. I turn on the machine and hit the LASER button and look for a pulse or an ammeter spike. Anyway, I am not sure I know what you mean by "ballast", Dave. I would really like to figure out what, if anything, is the deal with the PSU (which i had no reason to suspect in the first place - it was the tube I was concerned about). No wiring schematics came with the machine so I am going to try and run those down as well.

BTW - thanks to everyone for helping. i could have destroyed my machine or myself if those of you who took the time to answer my questions had left helping me to someone else.

[Dave Sheldrake]

Would this prevent the ammeter from seeing current flowing out of the power supply when the laser button was pressed?

Yup it would as there is no circuit, bit like connecting the live to a lightbulb and expecting current to show on the neutral if it was left in thin air. (or connecting a battery to one side of a meter)

I am not sure I know what you mean by "ballast", Dave.

Not something to muck about with, it's basically a connection between the wires that can deal with the power without causing a dead short. effectively something to suck up all the power being put out so that the amps can be measured safely at the BLACK wire. Sadly there isn't any amateur equipment that can test the HV end (RED wire) and tests like that can be dangerous, VERY dangerous.

On the PSU itself there should be a button market "TEST" or a small hole marked "TEST" pushing that bypasses all the interlocks and sends current direct to the tube without checking for any errors. That will narrow it down to PSU Fault & Tube Fault or PSU OR Tube Fault. it won't tell you which one is the problem just that there is a problem with one or the other.

It doesn't really make sense that the PSU is broke.

I don't *think* the PSU is the problem, I think it will be the tube BUT that is just *think* I have no way of telling from the available information. The PSU may not have enough power to strike an arc in the bigger tube OR it may be the PSU is damaged, in reality the only way to test it would be by fitting a new tube rated for the PSU you want to test or having an HV specialist test it for you.

Rule out door switches etc first, if there is a test button on the PSU try that first then we can see where we go from there. (a 2 bucks switch is a lot cheaper than buying PSU's and tubes) if there is no test button on the actual PSU drop back and we can see where to go from there

best wishes

Dave