JDSU Argon laser stripping and cleaning.
By Leslie Wright
Ok you have just bought yourself a used argon laser, you take it home and plug it in, and as the seller says it lases well, but the beam quality is abysmal! Instead of a perfectly round spot, you are greeted with a fuzzy beam, that is surrounded by halos of optical "noise". The optics are obviously dirty.
This is not unusual among second user argons. Often they are run in dusty, or smoky environments, I think the ones out of nightclubs are probably among the worst.
The cylindrical JDSU heads are a pain to clean, because they are quite compact, however dust and crud rarely gets past the little window in the front of the head, that picks off a bit of light for the photocell, so this is what I will be showing you how to extract for cleaning.
There are a number of differences between heads of different years, so this is presented as a guide!, screws and suchlike may be in slightly different places, but the general layout is the same.
First of all if there are any labels present covering the join at the ouput end, they need cutting along the join they cover with a sharp knife, as it is this plate we will be removing first. Once these stickers are cut, remove the three screws (they may have allen heads) around the edge of the tube, closest to the output end, and gently ease off the end.
The front of your tube will look something like the picture shown above. The little black structure to which the screwdrver is pointing, is the photocell housing, that contains the little window. It may be possible to remove the photocell housing in-situ, but since we are in, we will check the OC mirror for dirt anyway. So remove the other three screws around the edge of the tube, right next to the row you previously removed, unplug the little plug off of the circuit board, and gently ease out the plate holding the photocell and circuit board. It is attached to the laser at the back by an earth wire, so you will need to remove the cap-head that secures this, once the plate is mostly clear of the housing.
Above. Removing the plate and disconnecting the earth bonding wire.
Now that we have the plate on the bench, there are just two screws to remove, either side of the photocell housing (shown above). The photocells legs are usually pushed into two small sockets on the board, but they will pull out, just take care not to bend the legs.
Above is a rear view down the barrel of the photocell housing. You can see the window in the middle. To clean this window, I suggest a quick blast of canned air, or dry nitrogen on either side. In the case stubborn dirt like the deposits from fog machines or cigarette smoke, try one or two drops of PURE alcohol (It must be the purest stuff you can lay your hands on! Lab grade is OK, spectroscopic grade is better, definately NOT the junk from your local harware store!) , on the window. Once the alcohol has been on a while, and before it evaporates, remove it by shaking the housing vigorously to remove the excess. Repeat as many times as necessary, until it looks clean. (If you look through it and you find it hard to tell whether or not there is glass in it, then its clean enough!) Avoid the temptation to stick things in there to clean the window with. If you scratch the window, even with a soft cloth, the damage will be irreversible!
Finally inspect the OC mirror, it will probably be clean, in which case leave it alone.
Refitting is the reverse of the above. Re-seat the photocell housing back on its plate, being careful to insert the photocell legs in their holes, and secure it with its screws. Offer the plate back up to the argon laser, and secure the earth bonding wires, and plug the plug back into the socket on the circuit board. VERY gently ease the plate back in to the housing. The plate seats arounnd the OC mirror, so if there is ANY resistance when pushing it in remove the plate, and try again, or you will bend the mirror mount.
Align the plate with the holes, gently twisting the plate if necessary, and replace the screws. Repeat the procedure for the final metal plate, and the job is done!
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Copyright © 2007, Leslie Wright, All Rights Reserved.