Lexel 88a pulsed operation

[ronny]

Hi,

there is a simple method to check a given ar+ tube on sams laserfaq(http://laser.k3pgp.org/Notebook/Lase...ps.htm#apspit1).

Can i use the starter which is already mounted in the head for this test? Idea was to power the magnet with about 150V, this will power the starter too and then periodical enable the starter with the relais.

Anyone tried this before?

thx!
ronny

[yaddatrance]

To save you some premature dissappointment. There is a 99.9999% chance the optics will need to be walked to
get a beam.

The only thing you really need to check is that the tube is intact (ionizes) and that you have a clear bore.
If you get a good clean ion glow (purple light) and you can shine a HeNe all the way through, then the tube
is good and you're going to be able to get it to lase. If it hasn't been run in a long time, it will be overpressure
so you may need to "kick" it with an external starter.

The "health" of the tube after you get it to lase would then be determined by the power output after it is fully tuned.

Than I woud run around looking for a real power supply. Gas lasers are traumatic enough even using certified
power supplies, but here's a guy who built his own SMPS http://perso.orange.fr/redlum.xohp/laser/lexel88.html

To answer the questions directly. Unless the tube is overpressure, the built in starter will work. Find out the max
voltage the magnet will take and run it at that. (Make sure it's well regulated and limit current!!!) The magnet
guides the ion channel down the tube. So the lowest number that gives good power is the normal setting, but with
hard to start tubes, max magnet is necessary.

Relays are fine if they are rated for it.

P.S. after you get the glow, and need help walking it, let us know.
P.P.S. Oh yeah, in case it wasn't clear... Current control is the most important thing about a laser PSU!... The voltage range are more suggestions, but without precise current control (specifically if you have overcurrent) you can cause cathode to sag from overheating, and that will block the bore. That is the most easiest way one can turn a laser head into a boat anchor.

[ronny]

Ok, understand.

The problem is that i get some heads and some different laser psus and i dont know about the state of all components. Thats why im looking for any "easy" way to check one thing after another.

All the guys said "it should work" but no one really knows about and i assume (as you mentioned) the optics arent 100% ok and some parts are overpressure.

I have for example an ZPS-2 psu (as i know its an lexel original one) but dont have any infos on it and no idea how can i check this w/o risk a tubes life.

So my first idea (after ive seen the pulse stuff on sams site) was the test with the starter to ionize the tube just for a moment - but ok when im note sure about the optics i will not see anything.

ronny

[yaddatrance]

Can you post a pic of that PSU? I'm not familiar with it.

[ronny]

this one:

http://www.ewoks.de/laser/psu1.jpg
http://www.ewoks.de/laser/psu2.jpg
http://www.ewoks.de/laser/psu3.jpg

It seems this one "just" controls the tube current (and feedback control of the light sensor (stability?)). There is no driver for the magnet or filament.

ronny

[yaddatrance]

Interesting. That seems a few design generations newer than an 88
and looks a little small for an 88 supply I won't say it wouldn't run
an 88 at all, but I can definitely say you won't get full power out of one
with it.

If you decide serious about using that PSU, then we can probably steer
you through modifying it to safely work, at least enough to run in idle mode.
You'll definitely want to crack it open and take careful pics of both sides of
all the PCBs you can get at.

[ronny]

ok

This one is water-cooled (i think its not visible on the pics).

I already started to open it and clean it so no problem to make some pics.

ronny

[dave]

That is a OEM switching supply for sure. We have one here, running out ALC909 single phase It does up to 32 amps, so you will definitely get full power out of the 88


You will indeed need a transformer for filament and magnet. Florian from ABSee laser sells these seperatly, so drop him a email..


I have all the details here for converting it, if you need them. Its actually a very easy process, it has voltage outputs for input and output current, as well as a input for current control..

Iv got the schematics as a photocopy, ill try to scan them in after the new year..

Dave

[yaddatrance]

Nice! Who sells those PSUs? If they do 30+ amps into a tube, single phase, I want one
Send me details on it, I have a couple heads I might convert over, since they currently
use 3-phase.

[dave]

Speak to Florian @ ABSee laser. He is a great guy, always very friendly and helpful

http://www.absee-laser.com/index.html

Since they are a switch mode supply, we can have our 909 running quite happily at 22/23 amps, off a 220v 16A breaker