Lexel 95 - working fine, but questions

[mophead]

Hey Y'all,

I've a couple of questions about this Lexel 95-4 some of you all saw (and fixed) at SELEM this year.

It works just fine, plenty of power, nice beam specs, ect...(once I got the tap settings closer to correct) But I have a couple of questions if y'all don't mind.

1. It doesn't seem to like lower power levels. The lowest it will go is about 1W or so. It doesn't matter if it is light control or current control mode. 1W is the minimum it will do. Mind you, I'm not complaining about power but for the things i'd like to learn about right now, that is too much power.

2. The beam coming out of the business end is nice, tight and bright - best i can tell. There is a small beam coming from the HR -- at a distance of 3-5 feet, it is actually 3 dots. Does this mean the cavity is not in good alignment, and if not, should it be corrected from the front, back or a little of both?

I think I spent too much time at SELEM playing BBQ dude and not enough time paying attention to the reason we were there.

Also,

Gogu just sent me a couple of AOM's to check out (Thanks man!!!!). I'd really like to play around with those and me scanners a bit, especially since the premierlaser's thread......


Yeah, a beam table would be sweet, but with the space I have, 2-4W is WAAAAaaayyyy too much power for now.

Ideas?


Something tells me i'm going to be looking for a Kr ion to go with the AR I already have soon... Damn money pit hobby.......

[mliptack]

Something tells me i'm going to be looking for a Kr ion to go with the AR I already have soon... Damn money pit hobby.......

You're not looking already?

Unfortunately I cant help you out with that question, but either way, do you have any pictures? I would love to see 'em, as I'm sure many others would too.

Best regards,
Max

[mophead]

but either way, do you have any pictures? I would love to see 'em, as I'm sure many others would too.

This is all i got for now. Haven't had a chance to get the AOM (just came this afternoon) and scanners going yet. Hope you enjoy.

[buffo]

I think I spent too much time at SELEM playing BBQ dude and not enough time paying attention to the reason we were there.

I hear you there, pal. This is why I think we need to re-think the whole concept of SELEM. Is it fundamentally an event where we go to watch laser shows? Or is it a repair, show and tell, kibitz and fix my laser projector sort of event? Is it a laser information seminar, or is it a big party? We've certainly proved that when you try to make it into all of these things at once, people get burned out and everything comes off half-assed.

I've been thinking about moving the presentations to a separate event. And maybe it would be smart to just have everyone meet at Pizza Hut for lunch. (Or someplace like that.) Don't get me wrong - your BBQ was awesome, but it also meant that you and your wife spent the whole day in the kitchen on Saturday. Not sure at all what to do about the repair side of things...

I guess this really belongs in another thread, but since you brought it up it got me thinking again. Sigh...

Yeah, a beam table would be sweet, but with the space I have, 2-4W is WAAAAaaayyyy too much power for now.

If it will only idle down to a watt, you could always put a neutral-density filter in front of it to attenuate the beam even more. Heck, even a pair of sunglasses would be better than nothing.

Adam

[mixedgas]

Lexel that wont turn down, but also regulates, thats a new one......
There is no I min in current mode, it should drop down to zero and loose the plasma ignition/

Sounds like the protect zener on the passbank is conducting or the psu has been modded. I'd also look at the metal "bathtub" cap in the head, because if its open circuit, the ignite pulses will start to drill into passbank parts.

Need 2 think about that, give me a day or two.

Steve

[Laserman532]

1- not too concerned about power output...what is the current (in amps) at minimum knob position. There would be a trim pot on some PCB somewhere where you can set minimum operating current level, just as there is a trim pot somewhere on some PCB that sets max current (steve can get this info for you)

2- the hr might have a slight wedge to it to prevent some kind of etalon effects. you may be seeing three dots due to multiple reflections in the hr substrate each one getting progressivly dimmer. little spots separation...less wedge...more spots separation...more wedge

it is a 2 minute job to walk the mirrors with respect to each other to see if ya go up or down in power. walk each axis for maximum power...want more power...move the plasma tube around.

[mixedgas]

Quotes are in Technicolor....

1- not too concerned about power output...what is the current (in amps) at minimum knob position. There would be a trim pot on some PCB somewhere where you can set minimum operating current level, just as there is a trim pot somewhere on some PCB that sets max current (steve can get this info for you

)

L95s DO NOT have a min current circuit.


2- the hr might have a slight wedge to it to prevent some kind of etalon effects. you may be seeing three dots due to multiple reflections in the hr substrate each one getting progressivly dimmer. little spots separation...less wedge...more spots separation...more wedge

Lexel uses a little wedge. 1 spot off the main beam is typical for older lexel optics. its the reflection from the output face of the mirror.


it is a 2 minute job to walk the mirrors with respect to each other to see if ya go up or down in power. walk each axis for maximum power...want more power...move the plasma tube around.

Cant move the P tube on lexels. Fixed at the factory by using really good machining. A advantage of using cylendrical shapes for everything. Walking you can do however.

Mophead, if I remember right yours was one of the ones that needed the pivot screws adjusted on the mirror plate after we got done.

Steve

[Laserman532]

cant move the PT on lexels...sounds like a design flaw to me

No minimum current trim pot? What makes it idle...just the tube pressure, magnet parameter, line voltage, tap settings, room temperature, water temperature? sounds silly to me (i am sure you are right but it still sounds silly to me) there again...another design flaw.

dosnt moving the pivot on the end plate only change cavity length and in reality have nothing to do with x y adjustment (of course you have to peak xy again after moving pivot but that should have no real consequence of what he is talking about.

multiple spots is the wedge and multiple reflections inside the hr...want to get rid of them? sandblast the back side of the hr...they are gone. the wedge is there to keep the laser from getting lasing from the back side of the HR creating etalon effects...is my best guess...but hey...what do I know

IMHO - lexels were only slightly higher on the food chain than American laser or control lasers...both of them CRAP!!!

[mixedgas]

cant move the PT on lexels...sounds like a design flaw to me

No minimum current trim pot? What makes it idle...just the tube pressure, magnet parameter, line voltage, tap settings, room temperature, water temperature? sounds silly to me (i am sure you are right but it still sounds silly to me) there again...another design flaw.


NOT exactly a flaw, the supply is rated to control the tube down through zero plasma. You can turn the plasma out with the knob. I've seen them sustain at 3 amps. All you have to do is hit ignite if you drop out.


dosnt moving the pivot on the end plate only change cavity length and in reality have nothing to do with x y adjustment (of course you have to peak xy again after moving pivot but that should have no real consequence of what he is talking about.

At Selem he didnt quite have enough adjustment range to fully walk the tube, so we got him near lasing and tossed him aside for doing the next 11.
I didn't have my bore centering adjuster rig with me. On a Lexel, you use a 15 mm diameter brass PIG with a .6 mm hole down it to course align the plates with the tube, using a hene. You can then drop in ANY tube and Any magnet and need no more then a half walk to full power. Somebody had turned the wrong screws or walked the resonator around a scratch on his head. Normally they are locked by a compression clamp.

IMHO Its a plus, NOT a flaw. The factory made the tubes inherently centered during manufacture. I saw the jigs to do this. Better machining, because the magnet forms the outer cooling wall, the ceramic part of the tube is the inner. The ceramic is clamped with rubber Orings at the anode and cathode ends of the magnet. You can get away with this with precision machining of the ceramic and magnet. Plus he has internal gas returns and his anode seal is air cooled and dry. During brazing a centerless ground tungsten rod runs down the center of the bore, forcing the segments to align.

This works great unless you have Florida water, which eats the brass.

If Lexel would have ever bothered to fix the damn fused silica brewsters, they could have burried SP. They tried at the end, making the "CQ" brewster, and Brian has UV grade crystal quartz on his Cambridge made Lexels now. Brian has massivly updated the design, and I'd love to own a modern 95L.



multiple spots is the wedge and multiple reflections inside the hr...want to get rid of them? sandblast the back side of the hr...they are gone. the wedge is there to keep the laser from getting lasing from the back side of the HR creating etalon effects...is my best guess...but hey...what do I know

Lexels only sandblast their cheaper optics, he may have a OEM hr. Or he has one of the few older OCs with no AR coat on the output side.
I'd urge him to only sandblast the HR's center, due to the way Lexel mounts them.


IMHO - lexels were only slightly higher on the food chain than American laser or control lasers...both of them CRAP!!!

Pat,

We can have that argument once you admit the I90 is better in reliability per watt then the old SP glass/beo tubes. Notice I did not say better in Noise or pointing stability, there is reason you rarely see etalons for Coherent's 1 meter class lasers. I know what that reason is, because I retrofitted I90s with etalons by Lexel and Sp.

Don't get me started on the 20xx and later series monsters with the bizarely huge power supplies. Or Beamlok, which is great in concept, but the execution is poor.

To your credit, you never had to deal with Beamlok or the UV 2050s with the active piezo controlled unstable by design resonantors.

This is all a moot point with the new sealed mirror water cooled tubes. Ie Star IIs, Sabres.

Steve

[Laserman532]

this argument (discussion) would be better off if it were a drinking game

the I90 is a fine laser I have never knocked the "big c"- too complex for the normal "laser tech" tho IMHO. Frankly, over designed pushed into market while law suites were flying back and forth. Invar resonator great! Pointing stability good, price was too high. I feel prematurely ejaculated into the marketplace.

20XX remember when you were dealing with the SP metal ceramics "in production" I had been dealing with them for about 5 years "under development" in labs with secure entry So I have experience...and have been in meetings where yelling happened. ahhhh good times, it was my job to evaluate products which had been handed down by gods

you and I know that the etalons were to narrow the linewidth of the mediums, the open cavity allows all sorts of fun things to happen such as etalons, mode lockers and cavity dumpers as well as frequency doubling.

Sealed mirror cavity designs??? I dont like them because of above statement.

are you drunk yet? hell...Im getting there

next week...dye lasers, ultra fast dye lasers, ring lasers, PDA's & OPO's