ALC68 strip down & clean - Help please

[chad]

I had one of these many moons ago. If everything was peaked up just so I could get about 3.2 watts out of mine for a short time.
I also retrofitted it with a pair of heavy duty squirrel cage fans. I could run it at 1.5W pretty much all day and the fans would keep it cool (enough). If I ran it at 2 it would start to smell like burning things.

There was something funky with the power supply. Every once in a while it would start to make a buzz and the power would drop. I kept a roll of gaff tape handy to whack the supply and it would go back to working correctly. I spent I don't know how many hours with a scope and meter trying to find that intermittent problem. Never did.

Good ole gaff never failed me though..

Chad

[buffo]

We had a working HGM5 at SELEM 2007, thanks to Jeff (Have_Unlockled). An HGM5 is basically an ALC 68 tube with shorter brewster stems. And as Chad and Aijii mentioned above, while the tube may be capable of 3-4 watts, that's for intermittent use only. With stock cooling, you're good up to a watt or so CW. 1.5 watts is *really* pushing it with the stock blower.

Jeff had a pair of *huge* 220 volt squirrel-cage blowers hooked to his HGM5 via a pair of ~6 inch diameter metal ducts. The thing sounded like a jet engine! But with those two blowers sucking lots of air through the head, he was able to run the laser continuously at 3 watts. The air temperature exiting the pair of blowers ran pretty hot though - 165 degrees F.

Personally, I don't think I'd want to push the tube that hard - even with all the extra cooling. 2 watts is probably more realistic, but even so you'll need lots of extra air flow to keep the tube cool.

Adam

[smogthemog]

Thanks for all the information guys. It's all gone in and is very helpful.

I have the head all stripped down now and am about to go off to work with a large bin liner of bits ready to be bead blasted. As you can see from the photo's it did need it, it was filthy!

The second photo shows the damage to the fins which would quite badly reduce the airflow.

[LesioQ]

Hey, I see this head has a tickler on the anode brewster stem! Perhaps there's also one more on cathode end. I suggest You be careful there when handling & connecting, as this is the favorite place to catch a leak.
As for the rubber collars - in higher power lasers these like to be vented from time to time as ozone is generated inside, causing undesired absorbtion intracavitally.

Piotr.K

[mixedgas]

Do you have your copper "hot dogs " or sausages? ie the important dessicant assembly that keeps the windows and mirrors dry ?

remember to shake and bake the silica bead dessicants, ie heat them in a oven to ~150 c , shaking very once in a while for about 2 hours. Then hold them in a pair of pliers and heat uniformally with a propane torch till you see "waves" of copper oxide changing colors as you move the torch around. Then set them on a brick to cool. If you have a piece of ~6 mm dia 6 cm long glass tubing you can slide on the ends, you can see the water come out and condense on the glass.

The manual calls for washing the brewster stem "o"rings in isopropyl alcohol before reinstalling. If you need new ones, they are made of "buna N"

Steve Roberts

[smogthemog]

Thanks for that Steve. The 'O' rings look to be in very good condition, they came off quite easily in the end after I first thought they where stuck but it was me being a little too hesitant.


Can an ALC68 be re-gassed and re-OC/NR mirrored to produce white light??

[QUAZAR]

Did that laser come from Sid Kamani?

[smogthemog]

I got it from a chap in Peterborough called Tony.
Ebay username: laser-vision206

[QUAZAR]

Ahh, OK.

Its just that it looks suspiciously like one I sent to Sid Kamani (Laser Animation) for repair. They are/were based in Grantham. I never heard back from him afterwards.

FYI, the one I sent in was painted black. The power supply had rack mounting ears on one side only. Where the cathode connections are on the tube, one of these had broken off, this was the repair I required doing.

Please look at the power supply, the resevoir caps in particular. Are they blue, as opposed to the normal grey ones? Have they been wrapped in tape to make the diameter wide enough to fit the cap mounting clips?

Dont worry if this does appear to be my old one, you wont loose it. My beef is witth someone else.

[mixedgas]

yeah, they can be whitelighted. BUt why, 2 of marconis maxy modules, 1 polarizing cube and a beam combining prism and your almost there, although the diode red is rather deep red,.

probably 350-400 mW while light , based on the exceptional one I did a few years ago, but a 40/60 chance of failure if the cathode cant take seeing air. Ie 40% chance your gonna loose it unles syou pay for new cathode and brewsters. Whitelighting with a excess red KR mix can drive the tube voltage down, so you can run it a little harder. I rate them as 350-500 mW CW argon unless you boost the fans to 4 big ones. Then its a 750-800 mW argon.

the $#%^ optics are 250-350$ a piece X 2 WHEN I can get them. only reason to do it is the yellow and violet lines.

so $225 x 2 maxys
40$ chinese pol cube
$120 or less in KM1s or clone mounts
25$ piece of high grade pass blue/green dichro from ONE STOP LASER
~40$ switching psu for maxys
GAWDAwLFUL amount of shipping $$$ (greedy oil companies)

VS ~1000- 1500$ german hack and pump fill job (probably 2-3K$ for new cathode AND BREWSTERS IN A REAL REBUILD
500-800$ worth of optics (if you want NO green just violets , blues, reds , yellows I can fix you up right now with medical optics for ~180)
+ Nasty EU shipping and import export tariffs.
Its easier to send it to HB laser right now then to pay transatlantic shipping.

ONLY REAL JUSTIFICATION IS IF YOUR OWNING a 12 CH AA Electrooptic (france) PCAOM, then you should consider it!

Steve