Old spectra physics ~35mW HeNe laser

I have an old spectra physics HeNe tube of unknown pedigree... got it off eBay in the mid 90's, and it ran great for a while, but it's been in storage a good many years and doesn't currently start. Since I haven't used it in ages and it's taking up space, I was thinking of bringing it down to SELEM to see if anyone wanted to give it a good home. I'm going to spend a little time trying some of the tips in Sam's HeNe repair page, but if that doesn't work, is it still worth anything if it won't start?

I can post pictures later this weekend if there's interest. It looks like one of the embedded units without a nice external case.

Zap it with AC. Does the tube even light? Is it up to atm?

Running, they go for between $800 and $1500. Dead, they're useless.

Roger. Well, sounds like it's worth cleaning off and poking a little to see what the story is. I won't have time for that until Saturday, but I will come back here and update after I get a chance to clean and try a few things.

Thanks!

Better tell Sam he needs to bring a known good PSU with the right connector.
The big PSUs die as often as the tubes do.

Steve

I had one of those on the top of a 4' high stack of laser filled crates after a show once, riding another foot off the ground on a fork lift on the way to the dock as I walked along side. The driver of the lift saw a girl he wanted to talk to, hit the brakes, and I saw that head roll off the top, slam into the concrete floor and roll out another 8' before it stopped, tube intact.

LUCKY AS HELL! :)

Send pics of cathode; if getter is bad forget it.

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Originally Posted by Eidetic

The driver of the lift saw a girl he wanted to talk to, hit the brakes, and I saw that head roll off the top, slam into the concrete floor

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AHHHHHH! Noooooooooooooo! I think my heart just stopped...

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and roll out another 8' before it stopped, tube intact.

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Whew!

Adam

I am planning to take the outer shell off Saturday and get a better feel for what the issues are... I will report back! The weekend can't come soon enough. :-)

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Originally Posted by tribble

I am planning to take the outer shell off Saturday and get a better feel for what the issues are... I will report back! The weekend can't come soon enough. :-)

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it's always weekend... somewhere.

why wait? ;)

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Originally Posted by tribble

I am planning to take the outer shell off Saturday and get a better feel for what the issues are... I will report back! The weekend can't come soon enough. :-)

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Be careful to pull the cover as straight off as possible, watching the anode pin wire so it doesn't hit as you do. Old anode pins are brittle and weaker. Be REAL careful when putting the cover back on!!!

It's a Spectra Physics model 907! Various tags on the assemblies indicate it was putting out about 31-32mW when I acquired it. I never measured the power myself. No power meter.

The getter is suspect, but in the dark the tube does blink that familiar pink glow when the PS tries to start it shortly after initial poweron. Some pulses only go about a foot from the anode. The third or fourth one usually lights the entire capillary but doesn't catch. Then it goes dark for a while, but the process typically repeats after a 5-10 second interval. I have not left the PS energized for more than 90 seconds at a stretch or so. I can hear some very faint ticking sometimes during the starting attempts. I have not yet tried to clean the tube or the frame, but plan to wipe the tube down with some alcohol and cotton balls. I have a vague memory of something power-supply-related occurring on a bench somewhere and things becoming iffy after that, but that could just be wishful thinking. The ground wire may have come loose and then brushed the frame, arcing slightly. Unsure why a ground wire would arc in those circumstances, but that's the memory, faulty as it may be.

There are heavy rubber boots around the glass tube holding the ballast resistors. I'm afraid if I cut them off to clean them I won't have anything to replace them with. Whatever sealant they used to glue the boots on is a dark, crusty affair now. The ballast resistors are 27Kohms each, and there are three.

The PS that came with it is marked 5000 VDC at 11-12mA. The PS part number is 900880059. It's a solid black potted brick type. ("My God... it's full of electrons!")

Pulling the Alden connector apart immediately after unplugging the power supply results in a bright blue and audible spark across the pins of the tube side of the plug. At least there is some significant capacitance there...

There are some dark brown patches aligned with the magnet pattern near the anode end of the tube.

I'm hopeful that this may just be a hard-to-start tube that needs cleaning, maybe some ballast resistor work, and a new PS.

Does anyone coming to SELEM have a HeNe power supply suitable to drive this tube?

Best,
Mike


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I found this page on cleaning and alignment of this laser, but I am not about to attempt brewster or mirror cleaning:

http://donklipstein.com/laserhtr.htm#htr907ca

Sounds dead to me. The brown stains in the tube, and crusty ballast seals indicate lots of use. Clean it up and hang it on the wall! :th_wink:

I concur with Bob if the getter is no longer silver/black but has turned white of disappeared. The brown bore crud and pink color Vs Salmon sound like end of life tube. The power supply may be OK; have to try with a good head. :) The ballasts seldom fail unless they crack. I have seen one cathode ballast glowing white hot from a crack...the tube started to flicker and I bet the power supply was hating it...:)

Just saw the picture; the tube is bad.

Well, nuts. Can it be refurbished / repumped? I am sad. It was a nice laser. Lovely beam profile.

Cambridge Lasers in Fremont, CA probably has tubes for it.

IDK if the color is that far off, but after messing with it for a while, I just could not get it to catch and stay lit. I may bring it to SELEM anyway and give it to someone who has use for the frame or other parts, or if anyone is interested in poking at it.

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