Close to figuring out the issue but need help

That sounds odd as most of these are 220V… :thinking:

I’d prefer 220V as it’s half the current draw…

I wouldn’t order one until you check it. The lights on the motor driver are on, so it’s probably OK.

I see no white wires coming from the transformer… ?


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The white wires don’t come from the transformer. They’re the ones circled in my last photo. The person who sold me the machine said to check them with a multimeter but he didn’t tell me what they’re supposed to read.

Check them for what?

Is the device labeled where the wires connect?

Why would you suspect the transformer?

You need to understand what you are doing when they tell you what to do. It’s more difficult for you and more so for us…

Good luck


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The guy who sold me the machine thought the symptoms were of a bad transformer. My guess is he wanted to know what voltage I was seeing there to confirm that. The left white wire is labeled L and the right one is labeled N. I’m getting 238v at the white wires.

If I hold down PULSE for more than a full second, the fuse still blows.

My LED 15 on my RUIDA controller is solid red and LED 14 blinks. Based on my YouTube research that is normal. Just thought I would confirm with you.

I thought you stated it was a step-down transformer and you’re getting mains voltage?

The motor drivers are working so I’d expect the power system is working.

The led you are referring to are OK…

Not sure what to have you look for… I’ll have to think on it…


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I’m thinking bad power supply or shorted HV lead. I’d probably disconnect the LPS and see if the fuse still blows.

When it’s triggered, does it lase before the fuse blows?


I have replaced the power supply and have the same issue. What is the LPS?

I have unplugged the right green connector and pressed the TEST button. The laser fires doing this on my old and my new power supply.

Correct. The laser fires. If I hold PULSE down, it fires for about a full second or two and then the fuse blows.

There is probably nothing wrong with either ‘laser power supply’ or lps, this is the HV supply compared to the 24/48V supply used for the rest of the machine.

If it’s firing, then it’s ok, it would probably go ‘down’ quick if it was a problem within the lps.

I still don’t understand how this was supposed to work when you got it?


I believe this is actually a step-up transformer. The machine is probably a 220V machine and being used with 110V mains.

This phrase made me think it was a 120V machine plugged into a 240V mains…

When he read the supply voltage to the low voltage ps, at 240V, I snapped to the misinterpretation.

Notice my post 21…


I read the same thing but interpreted it as “converting my machine from using 220V to 110V”. I say this because Chinese or European market machines are often sold on ebay for North American buyers with transformers built-in. And the reverse scenario would be fairly rare.

I assume that’s why supply voltage is 240V since it’s been up-transformed at that point. Seems high if it’s indeed meant to be nominal 220V but not sure the specifics on this equipment.

With a transformer, it can’t really ‘fail’ by having more windings all of a sudden, a drop in voltage or smoke, but I’ve never seen an increase in voltage. I suppose it could short out in the primary and the ratio change.

I don’t know how many of these I’ve replace and never ran across one that upped the voltage… I have had primary failures, but there is usually a major current change from the primary side…

I commented that I’d rather have 240V mains than 120V like we here in the US. Another place they didn’t listen to Tesla… :frowning:


240V would certainly be more efficient and flexible and make international exchange a lot more convenient. I’d think we’d need a better plug standard than we have currently for safety reasons, however.

As far as the 240V out of the transformer, the simplest explanation is that it’s actually intended as a 240V system, not 220V. But if not, perhaps it’s actually meant for 100V (as in Japan) but being fed 110V or 120V.

That makes sense…

If it fails because it 2V low it must be bad… mains voltage varies a lot.

In the end, IMHO, who cares if the output voltage/current is what you need… if the output is a problem, then look here.

I try to start with the issue and go backwards looking for where the signal appears… the last part with no signal is the probable failure… This has worked for me entire life of fixing electronics.

I would have never gone down this road. I’ve seen no indication it’s a what I’d call a mains power issue…

The photo clearly shows the green led’s on the motor drivers, I’d assume power on the Ruida also … too bad he cut that off in the photo. That pretty much ensures he has a low voltage supply working…

I’d speculate if the lps is drawing the correct power and the fuse blows, then the fuse is too small…?

I still wonder why he’s had this kind of trouble with a ‘working’ machine.

From the limited information, I’d advise changing out the lps, since you push it’s button and the failure occurs…


I like @micrololin’s suggestion of disconnecting the LPS and seeing if the fuse still blows. If it only blows with the LPS connected that would reinforce the notion that the fault is with the LPS or a short on the high voltage side.

When it fires for a duration, it blows the fuse. What can you test on the lps without it plugged in?

No other signals change from the controller when you press pulse.

Clarify the procedure you suggest…


Missed this earlier. In either case, however, it’s not definitive if it’s the actual act of the laser firing or the act of pulsing for a prolonged time that’s the source of the issue.

I’d suggest unplugging the LPS and attempting to pulse for the same duration that would blow the fuse just to make sure it’s not anything upstream from the LPS. Simple enough test. If it doesn’t blow then finger pointing back at LPS or downstream.

There might even be something within the power supply that heats up. Works fine till it heats up then causes enough resistance to blow the fuse. Same with a high resistance short to ground.

The fuse started to blow after repairing the HV wire and power supply change. Even a loose connection at the HV wire splice could possibly cause enough resistance.