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Thread: My ILT is *flashing* at startup. whats causing this?

  1. #1
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    Default My ILT is *flashing* at startup. whats causing this?

    When I was at SoCaLem this last weekend, I acquired thru a trade, an ILT 5490A.
    I got it home & powered it up & it started the first try. I let it run for a couple hours not knowing when the last time it had been run. The next night when I ran it, I let it run at the *recommended* max current level & let it run for 2 hours. The next night it flashed about 8 times(igniter pulses) then lit. I ran it at idle for 5 hours. the next night it had a harder time igniting. It took 30 pulses to get it to ignite. I let it run for 5 pulses each time before turning off the key & resting it for a few seconds. I read on Sams that the tubes don't like the start pulse as it blows off chunks of the cathode filament each time it fires. It now is having a harder time starting taking up to a minute to start.
    What is causing the tube to be hard starting? the fan is a squirrel cage fan ,the same one I used on my 60 X, sucking air out thru the top. The cooling is adequate, I believe, unless I really need the patriot or Comair-Rotron pancake fans.
    Is this a sign that the tube is at high pressure? Or is at end of life? Is the start current set too low? What is the cost of re tubing an ILT? And finally, if I use a violet wand from the early 1900, will it fry the starter card in the head & items in the power supply if I use it to start the tube.
    Thanks,
    Nate.
    Last edited by Vidal Wolf; 02-13-2011 at 19:13. Reason: Punctuation.
    Will there be three phase!!!!

  2. #2
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    Quote Originally Posted by Vidal Wolf View Post
    The cooling is adequate, I believe, unless I really need the patriot or Comair-Rotron pancake fans.?
    As long as the air coming out of the squirrel-cage blower is not hot (read: above 150 degrees F) you have adequate cooling.
    Is this a sign that the tube is at high pressure?
    Maybe, but it also could be low pressure, and thus end of life. Especially considering that it ran just fine for a while, and then started giving you fits, I'd be thinking low pressure. Usually a high pressure tube will get better with time, not worse.

    Can you safely measure tube voltage while it's running? That will tell you a lot. (Lower voltage = low pressure, higher voltage = high pressure) You'll need to log the tube current as well...

    Make sure you use a battery-powered meter to check it, and don't let the starter pulse hit your meter or it will be toast. If you're uncomfortable checking the tube voltage, DON'T DO IT. You can get the shit shocked out of you if you do it wrong, and if your meter isn't isolated you can damage your PSU...
    Is the start current set too low?
    Older tubes usually like to be started at higher currents. What are you trying to start it at now? (7 to 8 amps should be fine, but if you're down around 5 amps, crank it up a bit.)
    What is the cost of re tubing an ILT?
    Probably not worth doing. If you can find a cheap tube on E-bay, that's one thing, but buying a new tube at retail is going to be prohibitively expensive. If it comes down to re-tubing the laser, start looking on E-bay for a used head. (A 60X tube will also work.)
    And finally, if I use a violet wand from the early 1900, will it fry the starter card in the head & items in the power supply if I use it to start the tube.
    If the HV gets into the PSU, yes. There is a section in Sam's laser FAQ that deals with this. Check it out. (The ALC 60X and the ILT 5490 are nearly identical.)

    Adam

  3. #3
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    I have a complete 5490 series some place, if not its bigger cousin.

    Set it to idle, at about 5-6 amps, and let it set a day, running 24/7 One of two things will happen, it will clean up, or it will start to die. The passive gettering mechanisms in the tube do not like max current. Just let it run, no start/stops. Make sure the hot air from the fan is exhausted and not recirculating, and that any hose on the fan is very short, except for enough to guide the hot air away.

    track the tube voltage.

    If you have a ampclamp and can get at the cathode wires, we can make a good guess at plasma health, also if it has the cathode jacks on the side of the head, some do..


    Steve

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    Default Thank you!

    Buffo, Mixedgas, thank you very much for the information. my ILT does have the jacks on the side of the head & I will run it this weekend and do exactly what you have suggested. I have stuck the fan on a short riser for better stability & the hot air is not recirculating back into the head. One thing I did not mention is that the power supply is an older black model 400 power supply. is this a possible cause for alarm? or start failure? it has no controls on it other than a port for a remote,keyswitch and connection for the laser head.
    I will keep you informed on what the outcome is. I personally am mildly curious to see what happens when a tube goes low pressure. if it does die from depletion then I would be sad, yet satisfied that I got to run a tube to the very end.
    Stay tuned!
    Will there be three phase!!!!

  5. #5
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Assuming its all lines or prism (prism is inside, turn the rear vertical to tune), the optics are clean (don't try that at home on a ILT) what is the ratio of green to blue? if its visibly green when scattering off smoke, usually they are healthy. As the tube dies, 488 dominates. black psu = no problem, as long as the current control knob works.

    Steve

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