Laser on all the time

[John Hulme]

This thread has been edited for the FAQ- any continuity issues are mine. Gene

I have just purchased a second hand laser, it is the same model featured in the early RDWorks videos. I have installed a new tube, the problem I am having is the tube is firing constantly, hence lines all over the workpiece because the tube does not go off when it it not required to operate. I have the water pump connected to a power supply, not to the machine output (the plugs are different). The new tube came with wires already fitted so only needed taping, a strand of wire contacted the machine casing causing an arc, could I have destroyed the power supply. Any thoughts please. John

[John Hulme]

Hi Pete, I initalise the laser the head goes to the start position. I turn the laser switch on to begin the operation. The laser only stops firing when I turn the laser switch off. I can not send a pulse because the laser is always on. Sorry if this sounds compicating.

[Jeffrey Aley]

So - if I understand correct:
- power the machine on and intialize with no problems

- when you intiate operation of the laser to pulse ..it stays on

Did I capture the isssue above correctlyTrue or false

Hi Pete, since your Boss laser might be slightly different, let me point out how (my) Chinese Blue & White is wired.

There's one switch that turns on the low-voltage power supply. This powers-up the RuiDa controller and the steppers, and therefore causes the machine to initialize (find home, etc.). I even use this mode when setting up my jobs and do the "Go Scale".

There's a second switch that turns on the high-voltage power supply. On my laser, the extraction fan is also hard-wired to this switch.

I believe the original poster is saying that when he turns on the HV power-supply, the laser is always on. It is not responding to the "laser on/off" signal that comes from the RuiDa controller. IIRC, this is a common failure mode for the HV power supply.

Regards,

-Jeff

[John Hulme]

Jeffery, this is correct. I turn on the laser control switch, then I turn on thelaser switch. The laser fire up immediately and sends the beam to the workpiece even though I have not started to run a file. Jeffery, do you think this is a power source problem. Surely the beam should not fire until the program file calls it to cut or engrave.

[John Hulme]

Thanks gentlemenn, the power unit is not very expencive, about £80. I will purchase one and let you know how I get on. Once again, many thanks.

[Jeffrey Aley]

Thanks gentlemenn, the power unit is not very expencive, about £80. I will purchase one and let you know how I get on. Once again, many thanks.

Anecdotal evidence (in other words, not my personal experience) shows that some of the cheaper HV power supplies have a very slow slew rate. In plain English, that means that there's a noticeable delay between when the controller says, "turn on the beam" to when the beam is actually on.

Based on this, my advice would be to avoid the cheapest-priced supplies and get something in the middle of the price-range.

One person who I trust has said that the MY-JG 50 is a very poor-quality power-supply, and recommends the HY-T 60 instead.

Good luck!

-Jeff

[Tim Mellor]

Without seeing or knowing about the specific Laser if you are getting a Beam that doesn't switch on when asked and is stuck on the 'HV part of the Power Supply' itself is unlikely to be the culprit.

I would be looking to either the output stage (less likely case) of the controller which is used to genertate a logic level (generally 0-5VDC) which is then sent to the input side of the Power Supply. If you know of someone with an Oscilloscope this is easy and safe to test and eliminate. If this output is locked high or low (depending on the logic the PS needs) then the PS will stay locked on.

Or what is more likely is the input switching side of the Power supply has a blown component. If you have a tame Electronics nerd at hand this is also fairly easy and safe to test by simply disconnecting the HV Transformer (this almost certainly will be fine so keep it) and looking at the signal that would be going into the HV. Worst case you are only dealing with mains voltages at this point. What you will be looking for is a component that has failed to a short circuit which happens or potentially that shorted component has taken out others. Chances are if you lift the lid on the power supply you will see where the magic smoke was released.

Lift the lid on you PS but be careful of touching a Capacitor they bite and can hold charge for quite a while

My PS with the lid off.

[John Hulme]

Hi Jeffrey, I'm guessing the 60 in HY T 60 relates to the wattage. My tube is 50W, would this unit be ok?

[Jeffrey Aley]

Without seeing or knowing about the specific Laser if you are getting a Beam that doesn't switch on when asked and is stuck on the 'HV part of the Power Supply' itself is unlikely to be the culprit.

Just to be clear for those who are new to all of this, what Tim is referring to is the stuff INSIDE the HV Power Supply. Within that box, (which he pictured), there's some low-voltage circuitry, and then a big transformer (the big white thing at the right of his photo) that turns mains (line) voltage into several thousand volts.

One could fix it (if you're qualified), or one could just replace the whole "HV PS" box. Personally, I'm qualified, but lazy - I'd just replace the whole thing.

Regards,

-Jeff

[Jeffrey Aley]

Hi Jeffrey, I'm guessing the 60 in HY T 60 relates to the wattage. My tube is 50W, would this unit be ok?

Higher wattage supplies are fine. Lower wattage supplies are not.
One might have problems if you go with TOO high a wattage (e.g. a 100W supply for a 50W tube) because you might have problems programming a low-enough output for etching thin materials (e.g. paper). I'm not sure about this.