Tube / power supply mis-match

[Dave Vigness]

So, how far apart has anyone gone? I seem to remember someone saying they ran a 40W tube on their 100W supply for a while when the tube died. If so, how long did you do that, any problems?

My PS for my 80W is acting up near as I can tell. I may have a line on a nine month old supply, but it's for either a 130W or a 150W. It has the spot for the access to the trim pot to turn it down, so I'm hopeful I can use it on my 80W if it comes to that. Turning it down by percentage through the controller would be almost a 2:1 change from my current set up. Doable, just have to be careful and make sure to set the max percentage.

[Tim Mellor]

There is more to it than simply reducing the percentage. I don't know enough about Laser Physics but I would also worry about the Voltage the supply is capable of. A very quick glance at 80W supplies shows some of them at 24-25kV while some 150W supplies push toward 'claimed' 50kV. If the internals of your tube can't handle the voltage peaks and it causes arcing bye bye tube

As someone with an Elec Eng background with limits on Laser Physics knowledge I would say WAIT.

I currently have paper and spec sheets out looking at what supply to get for a Reci 100W W2 and the Chinese so called spec sheets are

fryingpan.gif

[Dave Vigness]

Yeah, the specs give the max current. I know I have read posts, either here or one of the other forums, where somebody ran an old 40W for around six or eight weeks on their 100W supply. Granted it was an old tube that they were using in a pinch. I'm also unclear as to what turning down the trim pot actually does.

My head says that 'turning down' the supply via the controller is a stop gap akin to using a dimmer on the ceiling light. Buuuut, I don't know that for sure. And getting any kind of reasonable solid answer from a supplier is beyond hope. They are too afraid of responsibility / liability. I'm not familiar enough with lasers to know if the beam is generated on a combination of voltage and current, or if the voltage is a semi constant and only the current is varied.

I have a lot more research ahead of me, I was hoping somebody here had been through something like this before. So far the PS seems to be hanging on, it just has a little trouble 'getting up in the morning'. The first bit of operation is a bit weak and then everything settles in.

[Tim Mellor]

Re watching this one of Russ's. Not sure if there is any clues in it but I will time stamp it if I see something https://youtu.be/5CoTrLNUWTM

RDWorks Learning Lab 97 Understand Your HV Power Supply via Florida

Warning here but sort of us we both understand the Tube might go South due to the potential available https://youtu.be/5CoTrLNUWTM?t=2300

[Dave Vigness]

Yeah, From what I'm picking up, the voltage is relatively constant for a given wattage of tube over a small range. It's the current that turns the output power up and down. The only question then is what does the trim pot adjust, the current or the voltage.

[Tim Mellor]

The 'Potential/Voltage' would still remain my concern as the Supply when first trying to trigger the Laser can hit that peak by design. That is the place where initially you can damage coatings and surface. The over current is then problem number two and can be dealt with by changing the PWM from the controller trying to hold it below the point at which damage occurs at this point the voltage is then 'in theory' at a steady state but in practice most likely still spiking above the existing smaller supply.

[Dave Vigness]

Yeah, I had a feeling it was going to be one of those - it sounds good but it doesn't work ideas - but you never know if you don't ask.

[Dave Vigness]

New wrinkle:

Got an email from a guy that deals with Cloudray and had asked a similar question. He got a bad ChiEnglish response, but this is the gist of it.

Seems you can use a larger power 150W supply on a 90W, but loose control precision. I'm assuming the loss of precision is the expected power output scale need between the 90W and the 150W

If you use a power supply to small, 90W supply on a 150W tube, you work the piss out of the flyback and it dies an early death.

[Tim Mellor]

The lack of precision is only a controller thing in that the PWM it sends off to the Power Supply will be say 55% of 100% assuming 55% is full power (so 550 possible settings instead of 1000 points) which doesn't really matter much at all as no one really uses the decimal point after the power that I can think of.

It is what the transient response of the power supply is to an on signal which is some of what thew video talked about in that is it an aggressive or tame (SLOW) response to that signal. My Electronic Bench power supplies I use for example all never exceed their set point when turned on but some of the cheaper ones are known to spike well over any set point (transient) in this case they are prone to randomly blowing up low voltage micro controllers in particular.

[Dave Vigness]

LOL, and your neighbors don't like the smoke signals, or is it the creative language when it happens... LOL

I'm just glad I have the option if I need it. So far the PS just needs a few seconds to get to work. Most of the time it's more like micro seconds. If I'm just cutting shapes, on the very first one it's like I put a bridge in. After that it behaves just fine.