Liconix 4240N tuning

[GooeyGus]

Ok so I finally got all my power supply issues worked out on this liconix laser. It has 442nm optics and is the 'dual cathode' head. Really really neat laser.

Anyway, After aligning the optics, running it for about 25 hours, and making sure everything else seemed good to go, I'm only getting around 20mW of 442nm light.

The head has about 3000 hours on it, so I'm pretty sure it has a bit of life left.

Anyway, I know there are ways to adjust the Cd heater among various other things, but I'm not one to just start turning pots for the fun of it

So I was wondering if anyone has any info regarding the pot assignments on the control card in the head. Also, I was hoping there would be a shunt or something somewhere to check tube voltage and current. There are around 5 or 6 test points on the control card but I have no idea what any of them are for.

Thanks!!

[mixedgas]

I PMed you with the name of a friendly guy at a maker of hecads.

There is something in the FAQ about the ratio of two yellow lines in the sidelight.

Otherwise I dont have a clue, except helium diffusion when you turn on the helium heater is irreversable. Heat makes it leach from the HE resivoir through a thin glass window into the tube, and thats a one way trip.


Steve

[dxs]

Hi GooeyGus!
So how did you finally solve your PSU problem? You got a spare hv module, or had it repaired?
Please share if you get any informations on the pot / test points assignment.
Otherwise, the guy we talked about when you asked me if I knew someone with a spare PSU has the informations you want (if you can reach him).
Thierry

[GooeyGus]

Ahhh yes... the great power supply Saga.

Well.. as everyone knows my first one worked great for a day and then half of it was dead when I tried to start it the next day. After a few hours of troubleshooting sparks were flying out of one of the transformers and then the fuse would just blow every time the key was turned.

I decided to keep it around for spare parts, but I didn't even feel like trying to fix it.

Fast forward a couple months, I couldn't find a 4240PSU ANYWHERE. Melles griot wanted $750 for a full rebuild with 1 year warranty, which is actually a pretty decent price if you ask me. Anyway, I had decided to send it in, but I wanted to go for one last ditch effort. I sent messages to anyone on ebay that was selling anything related to HeCd lasers. To my amazement, I actually found a guy with a 4240PS who was willing to sell it!!

So the supply was delivered to my house. I plugged it in and started her up. It ran perfectly! After running for a full day I put it all away and went to bed. The next day I went to start it, one side fired right up but the other side wasn't doing anything.... but right at the last second the other side clicked on and everything was fine again. It ran for about 5 hours with no issues, so I went into the kitchen to get some food. I came back and the laser wasn't running but the PSU was still on. Uh-oh. I tried several times to get it going again but only one side would fire.... I was very angry at this point. It seemed as if the exact same thing had happened with this PSU. But, after trying for a couple hours, it just clicked on out of nowhere. It ran just fine the rest of the day.

The next day only one side would fire, again. The other side wasn't even trying. I decided to pull all the power transistors, test them, and clean and re-seat them. After I did that it started right up! Problem solved, right? Wrong.

The next day the same thing happened. This time I pulled out the HV modules and swapped them to see if the opposite side would work. I turned it on and both sides worked again. This wasn't the result I wanted as I knew I didn't fix anything. It worked great the entire night. Fixed, right? Nope... try again.

I started it up the following day and the same side continued to work, while the other was dark. This was a good sign as it told me that the HV module was NOT the problem. At this point I decided to work my way backwards. the next circuit in line before the HV modules were the PWM cards. I pulled these out and swapped them. FINALLY I got the result I was looking for. The opposite side now worked and the side that was working before remained dark. So I grabbed a PWM card out of my 'parts' PSU and swapped it in there. Both sides worked! I took out the replacement and put the original back in, only one side worked! I put the replacement back in and both sides worked again. It has worked flawlessly ever since!