Just recently replaced my k40 tube with a true 40w and now im getting that small squeal that i’ve heard people mention before. It sounds as if its coming from the power supply, but other than the sound, it seems to still be running fine. Anybody have some thoughts on if i should be worried or not? Thanks in advance for any insight.
you may need a new PSU - sounds like this one is being over taxed by the higher draw of the new tube
i was afraid of that. was hoping that maybe the mA’s could be adjusted on the PSU (if the sound was an issue at all, that is)
my power supply does say 40w on it though so technically it should be just right for the new tube. or am i wrong for assuming that?
Just because your car engine can spin at 9000 rpm does not mean you will constantly be driving it like that.
Get it? 
Are you saying that most power supply’s are rated at a higher wattage than the tube you want to run?
Or should be rated higher…
It should be. I wouldn’t want to run my PSU at full power to sustain the tube. I’m not saying you can’t do that, but just like with running the tube at full power, you will shorten its life dramatically, the same will happen with the PSU.
Gotcha. Yeah that makes sense. I should also add that it only makes the noise when on occasion when cutting. Engraving seems to be fine. I’ll look into new power supplies. I guess I assumed that 40w tube and supply would be made to go hand in hand. Now that I’m thinking about it, could a lower watt tube be overdriven by a higher watt power supply?
Yes, but not recommended.
By overdriven I meant to say driven too hard. Like in a bad way
The PSU supplies the power the tube demands - upto the limit of the PSU, so no it wouldn’t overdrive the tube. I remember Light Objects selling upgraded PSU units to use when you use the full 40 Watt tube - you might check them out - the stock ones are somewhat marginal - even for the 32 Watt tubes
@greg_greene , saying a PSU will not overdrive a tube is an invalid statement. A PSU can easily overdrive a tube, if the tube is less than the PSU. Take a 40W PSU, and a 35W tube, you can easily push the tube to 40W (and ultimately destroy it in the process.)
And plenty so called “40W” Chinese machines actually have a 35W tube in them with a PSU that can drive 40W …
So im having a hard time grasping this then. A 40w PSU isn’t quite enough for 40w tube, but if you have a larger power supply than tube it can destroy it as well?
I didn’t say an equivalent PSU isn’t enough. I said, you wouldn’t want to drive it at 100% to sustain the tube.
A larger PSU is better, and since you control its output, you can lower it to match the tube. and in the process extend the PSU’s longevity.
You can put a V12 in a Mini Cooper, doesn’t mean it will survive it. Similarly, you can put a V4 in a large dump truck, doesn’t mean the engine will survive trying to drive that thing loaded.
Basically, you can put a 100W PSU in the machine and drive it at 33% for a small 35W tube. No issues. Just don’t run it any higher.
Ah! Gotcha. Thank you
What does the current meter read?
What coolant are you using?
Current meter reads at normal powers. It has a really small bump in power when the sound happens, but nothing of any significance. I did notice now that the color of the beam inside the tube intensifies when the sound happens as well