UK Laser Meet #3

[Laserman532]

Pat
I suspect it didnt boom on start as It was dry inside the connector at this point. There must have been some moisture in the umbilical sheath as the connector was bone dry - I checked this and dried it thouroghly and between all the cables as far as possible up the umbilical. This has to have been caused by water and the only place it could have gotton to the connector was if there was residual moisture in the sheath. So when I set up, the laser would fire but we had water flow issues that meant it would only run for a few moments at a throw.
Eventually we got water flow sorted and the head fired up. It ran for maybe 5 mins it may be more - It didnt seem longer than that. As I said I suspect that there must have been moisture in the sheath that then sweated to form the droplets that caused a short that shut it down by flipping the front panel breaker. On trying again the mains breaker flipped so I didnt get as far as the start pulse after that. I hope this makes sense.

So I need to strip the connector out and examine the slices? I could not see any actual arc traces when I examimned earlier, though I would be lying if I said I had examined it thoroughly at this point. It was more just a general black dusting on the cable insulation and the insides of the amphenol connector shell halves. I will take a proper look tomorrow and look for the slightest run of arc trace - hell there must be one as it did obviously short out! I knew this was a bad bad thing to get the connector wet - In transit the water and the power connector are always sealed in separate bags and put as far away in the case as I can get them to keep them from coming into contact.
If it didnt see a start pulse - which it didnt in the wet state (I had a pretty good idea of the consequences of that occuring) then what are the key things appart from the oreo slices that I need to pay particular attention to?

Thanks for the heads up - despite it being bad news - I would rather know what Im in for in advance than find out the hard way and have to try and catch the bits as they fly past my head !

The Irony is that the outer sheath has NEVER been properly anchored into the conector housing - hence how I was able to get water in there, so I had taken the opportunity to close this off properly and had pushed the outer sheath into the rubber boot on the connector housing to seal it all for the first time since ive owned it! I guess there may have been a chance of that moisture venting and not getting to whrere it did if I had left it open -

Rob

Rob, couple of things...what happens is when people dont drain the head and they hook the two hoses together for transportation (i dont do this) What happens is water drips or splashes fall on the pin end of the connector and water "wicks" through around the pins and into the connector parts and between the two "oreo" pieces, which is where the arcing occurs, you wont see it until you remove the round spring clip and removing the "oreo" that is showing. No worries about pins being messed up because there is another "oreo" holding them together. (i hope i explained that well enough for you)

Please check this for me...Open the head cover and tell me if there is ANY evidence of water leaking from the "anode t block" and touching the magnet housing. (basically a "wet short" between the anode and magnet) Without seeing it...this sounds more like a possibility because you said the laser started...then dropped out. The best way to test this is to...hook up head and flow water and look for a slow drip to occur between the anode t block and magnet (the anode t block is the shiney metal part that the red wire is bolted to. This problem is WELL KNOWN as the "sacraficial anode" problem or electrolisis of the anode block.

let me know.

pat b

[stanwax]

Hi Pat

I see what you mean there has indeed been arcing between the oreo pieces - one pin is actually melted away - its one of the wires that is connected to the light sense photodiode. I traced it back and 3 wires go into a shielded cable that connects to the PD in the head. The wire that is nearest the ground pin (fat green cable - which in the head is grounded to the chassis) is the one thats broken and the earth pin itself has a piece of its collar eroded away.

As I had never heard this term 'oreo' before I assumed it was the material the blocks are made from - a quick google however gave me a different answer...A biscuit! sorry a cookie.

The chared surface of these blocks does seem to clean up easily though there are clearly 'eroded parts'. I will need to strip the pins out and see how well I can clean this up obviously I want to remove as little material as I can. I assume this material is selected for its mechanical but also electrically insulating properties - is there anything of similar electrical properties that one could use to remake the part - I have a lathe and as long as I can accurately place the pins this would not seem a tough thing to make.
If I unsolder the wires, I assume the pins will push out forwards away from the wires?

I will take some pix later an let you see the damage. To me it looks pretty messy and you may well agree, or you may say - 'hey I've seen much worse than that!'

Thanks for all your input

Rob

[stanwax]

Hi Pat
See attached images of the 'oreo' slices
for anyone who does not know what we are looking at this is the main connector at the end of the umbilical from the head where it connects to the SP265 exciter.

First image is of the pins head on showing the carbon blackening and areas that I have been scraping gently with a blade.
Second is the outer part with the stub of the burned pin showing in the lower centre of the image.
Third image - shows the pins again but side on - you can see the hole in the Ground pin quite clearly its the large pin at the back that is most sharply in focus.


I hope you can see clearly enough from these images

Rob

[Laserman532]

rob, fix the ground problem, dont worry about the photocell. (people sometimes blow those pins by referencing photo cell to ground if i remember correctly) If i were you I would buy an old 164,165 or 168 laser and rip the umbilical apart for parts. not worth making a piece or just replace the whole umbilical (if you are comfortable with removing the tube (total job is about 2 hours). I think the material is bakalite not sure tho. You really need to remove ALL carbon traces before reassembly.

Like i said, i dont think this is your real problem tho, It really sounds like a water leak between anode and magnet to me...maby so... but i cant see the laser... YOu see...the laser started and ran for 5 minutes. It is either the anode water problem, flakey interlock circuit, or flakey water flow or a flakey breaker (all of these issues will trip the inductor on the 4th leg of the front panel circuit breaker) Do you have a proteous flow switch? and is your water source (pressure and flow) SOLID???

Ya see... the laser starts and runs thats my clue. (this is a good thing...a bad thing is when it goes boom...

luck to ya

pat b

[Laserman532]

I was posting my last response before i saw these pictures... You are screwed, you will not be able to fix this with any reliability for future operation. You need to get another umbilicle, or umbilacle parts to fix this. This is pretty bad. ( I would try to buy an old laser head somewhere cheap and wreak it out for parts)

i am sorry, you will be able to clean it up but once arcing as bad as this has occurred it is almost impossible to remidy these parts. Check with brian at cambridge lasers, he may have something laying around. Sorry to be bearer of bad news but thats not a good thing.

I have done many of these repairs and the good thing is that your PS are good and so is your PT...this is just a little bump in the road

I still want you to check the anode to magnet issue i have been talking about.

[Laserman532]

I am sorry...I need to be more optomistic for you...YOU CAN DO IT ROB!!! I KNOW YOU CAN!!! I have to remember that I had access to repair parts so it was easy for us ...just replace it, no biggie...I forget that some people out there (you) are more resourceful than myself and due to the lack of parts you have to rely on your stealthy physic, cat like reflexes and alien intelligence. Yes you can "clean it up" But when i was doing shows..."my lasers had to be perfect" and VERY RELIABLE. You can do it!

[Insanity]

Guys,

Going back to the original conversation about a 2 day meet. One of lectures and one of lasering:

I am by no means saying that I am a guru, but know enough to have created my own workspace in Live Pro.

If you want to go down the route of training, I am a training consultant in my real job. I teach everyone from Sales admins to engineers the ins and outs of telecoms, Internet and private data networking all over the world. So have the ability and qualifications to make something very complex understandable to anyone. With the knowledge you guys have, my job would be easy and I would learn a lot too.

Therefore with my real world experience and fairly good knowledge of Live Pro, I would be happy to provide some form of Live Pro Training session.

Let me know and I will put something together. Would have done it last Sunday, but didn't want to turn such a friendly meeting into a scout camp.

I can buld an itinerary and add pretty much anything you might want to learn.

PS: I don't mean this to sound cocky, but love to help and share what I have learned.. I worked out how to build projectors from you guys, so feel I would be giving something back....

Mark

[Poso]

This sounds interesting.

[andy_con]

sounds good to me. im sure i could get up the cam and film it.

slight problem august might not be good for me !!!

[stanwax]

so we dont continue to hijack this thread - the SP168 fault discussion will now jump here - http://www.photonlexicon.com/forums/...3520#post43520

Rob