[kwiktsi]

My Chinese K40 laser broke today. There is part that looks like a big resistor that is hollow down the center. It has two wires attached to it- one in from the supply and a blue one out to the tube. It burned through today and arcs when power is applied so I obviously need to replace it- what is it called and where do I find a replacement? Also, is there anything that could have caused this to happen that I should look for? I have noticed it has been down on power for a while now, is it possibly related? Thanks in advance.
Joe

OK- spent some more time googling and found it to be the ballast resistor. Now, where do I get a replacement?? Thanks again.

[Fred27]

It's a 50W wire wound resistor - 50k if I remember correctly. I successfully replaced mine. I'll dig out the details of my replacement when I get a chance.

[kwiktsi]

Thank you. Please let me know when you find the info, I need this thing up and running . Thanks.
Joe

[Fred27]

This is what I used. It looks very different but works fine. I didn't connect the case to anything, just used the existing bracket to hold it in place.

http://uk.farnell.com/jsp/search/pro...-bf9f-00001000

[kwiktsi]

Great, thanks for the info, it gives me something to go by!
Joe

[herby08]

hi joe
this resistor size depends on the machine and motherboard, I remember that in one of my k40 it was a 3,6Kohm and in another was 5.8kOhm. but if this was burned out there is a source problem, probably the tube is gone and or the laser powersupply, replacing just the resistor does not help it will probably burn out again.
what kind of laser power supply do you have ? a couple picture would help to more exactly determine what is going on, also a descrption what you did as it burned out
how much power and speed etc.
greetings
waltfl

[kwiktsi]

Thanks for the reply. Upon further inspection, I did notice the blue wire was burning through and arcing to the chassis in one spot, so I don't know if that caused it or not. The resistor is a 50w 50k, now that I took it apart, I was able to see the numbers on it.

I was cutting something on max power because it has been down lately- took 15 passes at 6mm/sec on max power to cut through 1/4 birch- used to take no more than 4 at 8-10mm/sec! On the last pass, it started making a buzzing/arcing sound from under the control panel so I shut it down and that's when I saw the resistor. It has been getting weaker lately and I don't know if it is the tube going or now that I saw it, the blue wire arcing or the resistor going that has been the cause of it. The resistor is cheap, I was planning to toss one in and see how it performs then go from there if need be.

Here are pics of the resistor, I'll have to get some of the power supply and such. Thanks.
Joe

[Fred27]

That looks very similar to what happened to mine. I hadn't noticed a drop in power but was cutting on low power anyway. I had seen arcing to the case.

[kwiktsi]

Has yours been working well since the resistor was changed?