Tube / power supply mis-match

[Tim Mellor]

I do try and avoid the colourful language, last time of note the neighbors heard was when I got stung on the eyelid by a Bee. 'Mummy Mummy Tim said a rude word' was heard from the neighbors youngest In truth there was several and it may have continued for a while

As the voltage on the micros has come down over time so has the tolerance to voltage spikes. General Electronics like Laser supplies (24V Controller and the Laser ones) have gone switchmode which brings it's own set of issues including I suspect frying the odd Laser controller due to transients and ripple into them from budget supplies without proper filtering. Some of the controller ones can be fixed for the sake of $20-30 for a better supply (still switchmode) but given the nature of shave the pennies because the Westerners will only spend X we sometimes get what we deserve.

I was having a bit of a think about this and controllers and in conjunction with having a new build to do it might be a good time to have a dive into best wiring practices, supplies and avoiding or correcting some of the dodgy bits on others Lasers. So I might break out of the main build log into separate threads.

[Gene Uselman]

I think that a most excellent idea. I have been following this thread and finally used a mirror and flashlite to take a picture of the HV power supply on my machine. I have a 130w tube and my HVPS is a HY 150W by jnhy co. I have always wondered why I reach the top safe current for the tube at 45% power according to the controller- have always suspected the tube and PS were mismatched.

[Dave Vigness]

In some ways it makes sense. You need X amount of power to drive a 75W tube, and while not truly lineal, you would need X x2 power to drive a 150W tube. If a PS is designed with Y number of steps from 0% to 100% regardless of the max output, then a 150W step would be twice the increase of a 75W step.

I do not even begin to, or want to, understand the functions behind a flyback system. I am glad to hear, all be it indirectly but from a good source, that a company like Cloudray service department says PS over tube = good but sensitive. Tube over PS = smoke signals.

I also found out through another source, not as high on the totem pole as Cloudray, but not in the moat either, that the trim pot on the laser PS is on the 5V input. I have no idea if it caps the input and could be used to limit your max output, or if it reduces the input 'spreading out' your 0-5V across a say 0-3.7V spectrum. That would be something for you to give a try Gene, as you hit your max mA at such a low point. Tweak the trim pot and see if it changes your mA / % limit point. If it doesn't, it's a cap.

I will say it was a pleasant surprise given the extremely low quality control of the chinese laser cutter. I was all prepared to verify information I already had in that you could go up, and I assumed down, only one notch between tube and PS, and then only after verifying the KV specs. Before my decision to start on a whole new frame to transfer most of my electronics and such into, I looked at tube replacement options for my 80W. My MYJG80R power supply was plenty strong for my 80W, and by the specs and the SPT web site, SPT verified by email that I could safely go up to SPT's 90W tube, but no further. They specified the MYJG80 specifically on the web site, in other brands it would require a 100W supply.

Armed with the PS over tube information, I can comfortably pick up the larger PS if it becomes available and not worry. I am also comfortable in knowing that my current 80W supply will have a use powering a smaller tube instead of gathering dust down the road as well. Now I just have to decide on building a larger machine for just the large tube, or am I going to give myself a challenge and build a dual tube machine. I do not have a lot of extra space, hence the dual tube idea even being floated. And the 6445G is set up to control dual tubes with a measured off set... Hmmmmm

[Gene Uselman]

Cloudray actually has a POT setup for the PS and I was ordering some other toys so I have one coming my way. I bought directly from China and knew next to nothing about it back then... I ended up with good components, so maybe all those years of living right [ ] paid off.

[Dave Vigness]

POT Setup, as in how to adjust?

[Gene Uselman]

Potentiometer- yes- with the wiring and plugin for the...? Maybe it is for the controller now that I think of it. Don't get old... not pretty.

[Dave Vigness]

Too late

[Gene Uselman]

Story of my life.

[Tim Mellor]

I have had a good search of the forum and couldn't find a distinct topic on Matching Tubes to Power Supplies and why you should keep it somewhere in the ballpark. So I am adding this ramble and some potted thoughts here as to Matching Tubes to Supplies and allowing a bit of a safety 'fudge factor'.

1: Tubes don't die from not having enough Voltage to Trigger but WILL die from having to much current in a Triggered State.

2: Coatings on Tubes, Wires, Connectors and anything in the High side from the Power Supply can and will be damaged from to much Voltage causing arcing or insulation breakdown. Current here is not the problem less than 1mA at 50kV on a 20kV designed component will likely cause arcing or breakdown. So use an appropriate fudge level over the Tubes Trigger voltage but keep it sensible.

3: Using a power supply capable of grossly supplying an over current feed for the Tube in use increases the risks of killing the Tube. Keep it sensible and allow an appropriate fudge here too. To much fudge and you need to choke the supply down in percentage terms so you loose resolution and efficiency.

So how much fudge factor to allow?

Some of this is based on what I see 'some' Chinese companies do with more conventional Switchmode Power Supplies for non Laser use. It is NORMAL to see a design stripped of as many components to save a few cents and it is NORMAL to see the ratings of components pushed to and even above maximums. So bearing this in mind DON'T push your power supplies right to the limit.

What this translates to as a User is we should view claimed specifications for both Tubes and Power Supplies with Caution and healthy skepticism as to their actual truth.

[Tim Mellor]

Example Case and my current one and some of the thoughts to whittling down the list.

Picking a power supply for a Reci W2 Laser Tube. 90/100W. I did have a look at SPT as well and at the end of the day it was a bit of a coin toss and a gut feeling thing more than data to go down the Reci path.

Reci W2 Laser Tube
Trigger Voltage 24kV
Operating Voltage 18-19kV (differing figures online)
Safe Maximum Current 25mA
Peak Current 28-29mA (differing figures online)
Reci's own manual with some slightly different figures again http://recilaser.com/en/uploads/soft/20 ... 295042.pdf

Some of the options: Cloudray as a source and likely to be the supplier of choice for me but look around and add some others if you think they are worth a look.

Power Supplies I consider a NO

HY-C only offer an 80 or 150W version the 28mA maximum of the 80W is to marginal for the tube and the 38mA of the bigger one is overkill.
https://www.aliexpress.com/item/3258144 ... 31e4ooPhyB

HY-T only offer an 80 or 150W version the 28mA maximum of the 80W is to marginal for the tube and the 38mA of the bigger one is overkill.
** Seems they are badging the old 80W 28mA as 100W 'plus' https://www.aliexpress.com/item/3258371 ... 31e4AScVAv

Yongli YL-U1 & 2 similar reasons to above 28mA maximum for the smaller one and 35mA for the larger one (possible but still likely a no).

Power Supplies I am looking at MAYBE

DY13 nominal 100W 28mA 40kV and used a bit to partner with the W2. I would like to have a bit of space with the current for load factor reasons.
https://www.aliexpress.com/item/3258206 ... 31e4siIqhs

MYJG-100W 30mA 28kV. If the 28kV is a trigger voltage or maximum then is is a bit marginal IMO so some more research needed. Built in LCD.
https://www.aliexpress.com/item/3272173 ... 31e4OR2DLW

Power Supplies on the SHORTLIST

W120 35mA 40kV has about a 20% fudge factor on current nominally a 100-120W supply so would allow for a small tube increase later.
https://www.aliexpress.com/item/3258145 ... 31e4tOITzy

HY-Z100 45kV 32mA nominal 100-120W slightly less current but has some nice features of an external LCD display and a useful form factor.
https://www.aliexpress.com/item/3278305 ... 31e49tdyY1

ES100 45kV 32mA nominal 100-120W very similar to the HY-Z100 form factor without the LCD.
https://www.aliexpress.com/item/4000162 ... 31e4x7NViA

I will add some links here in the next little while but fell free to pick holes in the reasoning or add others for consideration