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Thread: JDSU 25ML Advice

  1. #1
    Join Date
    Apr 2017
    Posts
    5

    Default JDSU 25ML Argon Advice

    This forum was recommended to by a member in the LP Forum. I have an issue with my 25ML system that i am hoping for some advice. I will go thru what has happened and the tests I have performed. This will be a lengthy message so please bare with me.

    I have a Uniphase 2114 -25ML Power supply which is 20 years old and a 2211-25ML Head which is 25 years old.

    The laser was shipped to me from about 800km away. When it arrived the packaging was in good condition and both parts were wrapped in bubble wrap very well.

    I plugged it in and turned it on. After the 30 second timer it ignited on the first tick and showed a nice cyan beam. After a few seconds i could smell a burning electronic component from the Power supply. I turned it straight off. I snifffed the power supply and the smell was very weak and almost gone. I suspected nothing serious. I turned it back on and first tick the beam was on. Again the burning smell so I turned it off. I didnt know at the time but the seller had it in Light mode and the light setting pot was on maximum.

    I diss-assembled the power supply. I noticed a darkened area near the Anode output terminal on the top PCB. Fully removed and checked. It was a 10v 5w zener had failed. This zener was connected to the output of a small bridge rectifier. The only component on it. Appears like some sort of protection circuit.

    I bought a new Zener and installed it. Tested the bridge rectifier and is was fine. I tested other componets and could not find any other faults. All the PCB's look in excellent condition.

    Re-assembled the power supply. Turned it on. After the 30 second timer it ignited first tick. The beam appeared much dimmer now. I sniffed the power supply. No odd smells. Seemed to be running fine. But, after 30 seconds the beam went out. Ever since then I cant get it to ignite again.

    Tests I have done.

    Checked the filament voltage. It was running at 3.5 volts. Way to high. I found the switch for supply voltage was set to 220. I have 240-250 in Australia. I put the switch in the 240 volt position. The filament voltage is now 3.1 volts. At spec according to the manual.

    Checked filament while heating. A nice orange glow. Filament shape looks good.

    Removed the igniter board and checked it. I replaced the 10 uF 200 vdc cap for the trigger just to be sure. I applied 150 vdc to the board while I connected the ouput to a large CFL tube with a 65k ballast resistor. The CFL tube flashed about twice a second. Ignitor board seems to be working well.

    Re-assembled and tried starting again. I can hear the igniter ticking about twice a second. But no ingnition of the plasma.

    Tested the Anode voltage. About 170 vdc at the Anode output terminal inside the power supply. Then I put my oscilloscope on the Anode voltage at the power supply and looked at the waveform while it tried to ignite. Each time the igniter ticked I saw a small drop in Anode voltage. Varying from 10-30 volt drop from the 170v peak. The drop varied from about 1-10 ms then back up to 170 v.

    I tested the tube by connecting a 6 inch HeNe power supply to it. Their is a purple glow inside the tube with the Hehe supply connected. This was with the filament etc turned off.

    This is were I am at. From the tests I have done it appears their is not enough current flowing in the tube at 170v to maintain a plasma.

    This tube is old and looks abused. Their are burn marks around the center of it.

    I dont have another power supply or tube to be certain which is faulty. Currently my feeling is the tube is the problem.

    Any suggestions as to what I can try next would be much appreciated.

    Charles
    Last edited by Mosc007; 04-29-2017 at 22:57.

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