Can I use a 40w PSU with a 50w tube ?

[Jonathan]

It probably is...
In general if you have a device which requires 50W, but you're only using 70-80% (i.e. 35-40W) then you're operating within the rating of the power supply. So unless there's some other rating in the PSU that changes, it's fine.

Edit: Regarding rests, if you're talking about the laser then if it's just a thermal thing then switching off for 30mins every 3h is the same as running continuously at 83% power... which appears to be the case for you anyway.

[Want2build1]

Yes, Jonathan, I'd usually agree with your logic.

However, this is how I understand it so far, the tubes have a recommended trigger and running voltage. The power is controlled by PWM, so the voltage doesn't change for a tube and PSU pair. But higher and lower power tubes require a matched PSU. The tube lengths are specific to each power level. The 40w and 50w seem to be very close, so I am assuming it will be ok. (you know what ASSUME means ! ).

I wondered if a lower trigger and working voltage in the 40w PSU would be enough to run the 50w tube ... think, putting a small engine in a big car ! ... if it does manage to fire the laser .. might it shorten the life of the PSU ?

Just picking brains, before I try it anyway ! lol

unless , of course, anyone has a valid reason why I shouldn't :)

[Want2build1]

OK .. short answer is yes :)

My K3020 arrived today ... with a dead tube :(
but !
I wired up the PSU to my 50w tube and it fired up ok :)

I've ordered a 40w PSU £60 inc post ... and will report back further, when I test it.

[Want2build1]

PSU 2 died today
PSU3 fitted today (another 40w)
PSU4 ordered (60w)

30mA panel meter hooked up to keep an eye on things !

[Want2build1]

cut a full day ... no problems ..

obsevations ..

added a mA panel meter to observe tube power output .. stayed constant at 18mA throughout

PSU transistors were getting hot to the touch
Took side panel off the machine and pointed desk fan at it ... stayed cool
Will add extra cooling permanently :)

will keep you updated :)

[Want2build1]

another update ... 40w suply worked ok, the short time it was installed.... and will keep as a backup :)

Fitted the 60w PSU that arrived yesterday ... very impressed with it ... fro Cole-Tech ... ordered fri, arrived Mon, and looks like a decent bit of kit ! :)

1st test output 25 odd mA ... so had to reduce output to 63% to get a safe 20mA (Which I guess , in theory is the max I should push through ? )

done several hours with it so far ... it's cutting approx 40% faster than the original PSU (but I didn't have a mA meter hooked up) ... so all goo so far :)

all happy here :)