power dropped suddenly

[jarrodl]

I'm glad I found this site. It seems like a wonderful place for information and to buy replacement parts. Now to my problem.

My nearly new red sail x700 50watt laser went from 62watts at the tube a few days ago to 31watts today.(checked with a borrowed synrad digital meter) I have only used it a few minutes since it was reading 62watts. It seems like it did it overnight. It is running off a 120v to 240 volt step up converter. I dont know what the current was when it was running properly since it didnt come with an amp meter,( I found one on here and am going to buy it and put it on it so I can monitor current) but I put my mulitmeter on it and it showed 8mA of current. From what I read, it should be 25-30mA. One think I noticed the last time I used it. I was playing around with engraving a photo for the first time. It started engraving and after a few seconds the display went blank but the engraving continued until it was finished. After it finished, the controller reset itself and came back on in Chinese. Luckily I remembered the menu choices to change it back to english. It did this both times I tried the photo engrave. The next time I used the laser is when I noticed it didnt have enough power to cut the 1/8" acrylic that it was cutting easily before. The laser has less than 1 hour of use. It was bought by an individual that couldnt figure out how to use it and was essentially new when I bought it, although it is a little over a year old so no warranty. I had only used it to cut up until I tried the photo. I have run it less than an hour. I tried it again today and it was 5.5mA. I took these readings with the test button on LPSU to rule the controller out of problem
I figure it could be the tube or supply. Is there a way to test to know for sure? Could it be a ground issue? Is the ground wire from the LPSU supposed to go to the machine frame?
If it is the power supply, could I buy one made for an 80w RECI so when my tube dies I could upgrade?
Any help with this would be greatly appreciated.

[Tech_Marco]

First of all, it is a bad approach by using a 110V -> 220V stepping up transformer for the machine. What is power rating of the transformer? You better to have a 1000W step up transformer for a 60W system. In my experience, even 2000W and I won't say it is too much!

Second: you need to make sure that there is a good grounding from your machine to the AC output grounding. And, make sure it is a true grounding!! You have fresh screen and that telling me that you have grounding issue or losing cable.

For some LPSU (laser power supply) with bad quality capacitor, it won't be stable and it provide less and less current after certain time of usage. So many power supply manufacturers are trying to cut cost by using under rated Cap. "Ming Yu (铭宇)" from JiNan province is one of that who is using low grade and underrated capacitor in their power supply and ended up very defective rate, possible 20~25%. I was seeing a bunch of those dead power supply stack up in the warehouse where my friend was reselling.

There is actually no 50W laser tube in the market. If your tube is 1.0M (3.3ft) with 50mm (2") diameter, chance is that it is a 40~45W tube. The max current it could run on is about 18mA. If you apply 25~30mA to the tube, you're sentence the tube to 'dead' penalty. It won't last long and you could prepare the "Last supper" for the tube and say Goodbye.

For your reference, a true 60W could let you cut through 5mm acrylic at speed 10~12mm/s (roughly). It is hard to tell whether the problem is from the LPSU or from the tube. If the LPSU can delivery enough current, say 18mA and the tube still can't cut, the chance is that the tube is bad.

Hope this help

Marco

[jarrodl]

Converter is 1000va. I'm not a big fan of it either . I wired a plug straight to my breaker box to get my 240v. The current now measures 10mA and power of tube is about 38watts. Still not as high as before. I'm sure it was overdriven before, but shouldn't it be running about 20mA? It is a 39.5inch tube. Is there any way to tell if it's the tube or supply that's not working properly?

[jarrodl]

I am using a digital multimeter for my reading. Not sure how accurate it is. I ordered an analog one from this site. It may show a different reading. It seems odd that if it is made to run 40-45watts at 18mA that I am getting g 38watts at 10-11mA. I'm still not sure what changed overnight. I have checked all my connections.
I ordered the 30mA meter. It it just as simple as hooking it up in series with the ground wire on the tube? No shunt needed?

[Techgraphix]

It's not that simple, you also have to look at the polarity of the meter so it will turn to the right side...
So yes, it is that simple..

No shunt needed?

No shunt needed!
Kees

[jarrodl]

Ok. I found my problem. That burnt tracing goes to the ground side of the AC input and the ground side if the HV transformer as far as I can tell. My next step is to fix it. Could someone tell me how to safely drain the power off this so I can work on it? Also, what size wire would be sufficient to carry the current that the copper tracing was carrying as I have no way to repair with another tracing. This time I will use my handy dandy amp meter I got from light object to set my max current lower.

[Techgraphix]

With a handy-dandy multimeter you can check the voltages on the main capacitors.. If thes are within acceptable levels (near 0V) it is save to work. Other components like resistors, diodes, solenoids, transformes etc etc don't store energy. Normaly capacitors will loose their stored energy within minutes else you can just shortcircuit them with a (insulated) wire.. Yes it will spark and give a quite big crackle if they are charged enough..

Strange though.. I see a trace burnt that looks to be mounted to the frame on both sides (the holes) , so both sides should have the same potential and no current should flow there.. Or one of the components connected somewhere halfway drew so much current that these traces vaporized... I think you have a more serious problem then.. Unless your a master in electronics and can find and solve the cause, i would just replace the whole board.. Else it will get tricky.. Your working with real leathal voltages in such LPSUs

Kees

[jarrodl]

I fixed the trace, but it didn't fix the problem. The fuse going into the machine blew . It only lets one leg of the 240v in. So everything still works on the other. I guess that would explain why I am only getting half poer. I don't understand why the ground would cause that to happen. Marco, do you still do repairs on power supplies? What's the average turn around time?

[Tech_Marco]

Yes, I'm doing repair LPSU that I imported. Can you shoot me a picture of the front of the LPSU so I can determined if I can handle it. If it is buying from us, most likely I can fix it. It should take me less than few hours if parts available.

Marco

[Tech_Marco]

BTW, your tube is a 40W tube (39.5" = 1000mm). It is NOT a 60W. At most, it may output 50W if it is a good quality tube. In general, you don't want to apply more than 18mA for the 1M (1000mm) laser tube.

Plus, make sure water is under 25'C so that it last longer.


Marco