Trying to resurrect a CNI 589nm pointer.

[DJZ]

Hi all, ok, I purchased this pointer here about a week or two ago. I knew full well that it was dead but was looking for a challenge. I've got the thing disassembled down to the driver and pump diode. I'm suspecting that there is an issue with either the pump diode or the driver. Being a 589nm laser, I figured the output of the pump would be somewhere between 500mW and 1W. Well when I place anything at a focal point of the pump diode it doesn't burn it at all (I don't have a meter anymore). So I was kinda thinking the pump diode was dead. Well here's the output of the pump diode thru my camera, I would have expected something else other than what appears to be a clean output from the pump diode, it just appears to not be ouputting the power required for the rest of the pointer. So, I've checked diode current, 550mA. My oscilloscope is out on loan, however, to the best of my ability I can say that the pump diode is not being pulsed, though I have another 589 just like this one that is pulsed.

I have no idea if the pump diode is 1W or 2W rated, if 2W, it would seem that the diode is currently sitting below threshold and perhaps that part of the circuit that should cause it to pulse isn't working. What do you guys think? Am I on the right path here? I'd rather be working on an ION, but this has been an interesting experience!

 

[DJZ]

By the way, here are some additional pics of the dissected pointer.

 

[Helios]

Interesting! I am afraid I cannto help as I have not tried fixing a DPSS nor do I know much about c-mounts but I cannot wait for someone else to chime in so I can see some of that gold beam!

 

[Pontiacg5]

First, if you have another pointer like that one measure the current draw on the batteries and compare to the dead pointer. If they are close I would call it a diode problem, if it was extremely one way or the other I would say it's the driver. Either way, knowing the current draw of a similar working pointer would make it easier to guess what sorts of pump diode you have there. From there you can try driving the diode with another driver to make sure it is good.

You probably wouldn't be able to tell if the pump was being pulsed or not. You might try sweeping it in front of your camera to see if you can see the dashed pulsed output. Try a long exposure shot and a very quick sweep across a wall. Seeing as it has a large multimode output though whatever pulses the camera might pick up may just overlap each other making the output look CW, if that makes any sense...

 

[DJZ]

Hi Pontiacg5, the dead one reads around 650mA while the working one reads around 850mA. The more I think about it, the more I suspect this is indeed a problem in the driver. I tried tweeking both pots, one does tweek diode current while the other does nothing at all (I suspect this may have been duty cycle or pulse frequency). I need to find out which op-amp does what, it might be easy enough to turn this on CW without the pulsing just to test the pump diode. Anyone have a schematic of this driver?

 

[Pontiacg5]

I've never seen a schematic for a CNI pointer, I would say that finding one would be hard if not impossible. You would probably have more luck finding a used driver or completely replacing it with something else.

That driver does look like it's seen better days. Did you rework all of those traces or was that done by someone else? If you haven't tried already I would touch up a few of those solder points to make sure contact is good everywhere.

Sorry I can't help any more with the schematic, I've never worked on one of those pulsed CNI drivers before!

 

[Meatball]

What is the spec'd output of the this pointer? A 500mA driven C-mount pump does indeed sound low initially.

 

[Cyparagon]

^Most of the CNI greens used to have 1/2W c-mount pumps.

My 589 draws 1.06A. It draws less that that on crappy batteries, and stops lasing altogether under 700mA. How much does your battery voltage sag under load?

The output pattern on the pump looks healthy enough.

 

[Things]

Have you got another driver you could test the diode on? No point troubleshooting and rebuilding the whole driver if the pump diode is dead

How much did you pick this dead pointer up for? I'd love something like this to muck around with. I've realigned green lasers fine before, yellow would be interesting to try.

 

[rangedunits]

It was around 100$

 

[GooeyGus]

I would just rig up a simple LM317 driver to drive the pump with and see what happens.

Like you and others mentioned, the output pattern of the diode looks good. Give her some more juice and see what happens!

If everything starts working, then you can worry about getting the CNI driver to work again.