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Thread: Hi All!

  1. #1
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    Default Hi All!

    Hi there people,

    I am also new to the forum, and I must say it looks like there are lots of Laser mad people in here, which is great! I am based on the Isle of Wight (Southern England )

    Thanks to Laser Steve for introducing me to the forum and also got me started with Lasers after flogging me his Lexel 88!

    I also have a Spectra 2010 8 Watt Argon, which is a royal pain in the arse!

    I am hoping to go into using some DPSS stuff soon, but in the meantime would like to get to know some people on here and learn a bit more about certain areas!

    One question i would like to ask first off, does anyone have a trick to efficient alignment of a PCAOM?

    Cheers All,

    Alex

  2. #2
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    Hi Alex and welcome to the forum.

    This is THE place for laser addicts, loads of helpful advice, encouragement and witty banter

    Are you coming to the UK meet?

    Jem
    Quote: "There is a theory which states that if ever, for any reason, anyone discovers what exactly the Universe is for and why it is here it will instantly disappear and be replaced by something even more bizarre and inexplicable. There is another that states that this has already happened.... Douglas Adams 1952 - 2001

  3. #3
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    Hi Jem,

    yes I and my partner in crime are hoping to attend the meet next weekend, I may even bring some bits and pieces up to sell, would seem like a good opportunity...

    Also looking forward to seeing what other kit you guys have!


  4. #4
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    Smile

    Hello Alex! Welcome to PhotonLexicon. Hope you like it here.

    With regard to your PCAOM alignment question - do you have a bragg mount for it? I'm sure you realize that the angle of incidence for the incoming beam is crucial to aligning the PCAOM. Polarization angle is also important.

    Dream Beamz has a very nice mount for his PCAOM that makes adjusting these two angles very easy; not sure exactly who made it (Newport maybe), but you might want to PM him and ask.

    Adam

  5. #5
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    Jan 2008
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    Hi Adam,

    for the welcome.

    After looking at a basic tutorial I found on the net before about aligning them, it advised to start with the PCAOM tilted downward with the incoming beam entering and slowly tilt upward until you have the desired wavelengths, however I'm convinced it's not that simple, as I had it setup the other day in the workshop and had a reasonable out, without any ghosting, but the mount was offset at a angle and not straight,- the beam was entering the bottom left hand corner and coming out the middle right hand on the output window.

    By the way, how much output would one expect to loose using these devices, i have been told to expect around 75% of the total output of the laser head in question (In this situation a Lexel 88)

    I have considered ditching the Modulation and using a Z Galvo for blanking and actuators with Dicros on for colour change, but apparently, the Z Galvo's can be just as much hassle to setup and you will still loose a degree of output similar to that of a PCAOM

    Also thinking of getting the Lexel regassed as a whitelight (Argon/Krypton) with a new set of optics of course, can anyone advise at all? as much as we would love to splash out on some DPSS stuff, we just can budget for it at the moment!

    A

  6. #6
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    There are a few members here that can be of help advising/actually refilling your tubes. Mixedgas is one, search the forums, you will find plenty of info!

    And yes, Welcome to the forums! Enjoy!

  7. #7
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    One other question I have about the Lexel 88, it came with a step-down tranny, even though the AC in is 220v, basicaly it steps the voltage down about 10volts, surely the lexel psu would run straight off 230v without the transformer? I am asking as i'm afraid to try it in cases it screws the exciter (I'm assuming the fact it came with the laser would indicate it is required) although according to the web, the lexel supply should accept anything from 190v - 245v...

    Help appreciated..

    Alex

  8. #8
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    What type of supply do you have for it? The supply I had for mine had a buck boost transformer built in and was very easy to adjust for input voltages. If I recall correctly, the most important thing behind having it had to do with the cathode filament voltage/current and to prevent strain on the passbank. You really want to keep the cathode voltage/current within a real tight specification and the difference between having 190VAC to 245VAC was enough to cause problems. At least thats how I remember it, last 88 I had was about 8 years ago....

  9. #9
    mixedgas's Avatar
    mixedgas is offline Creaky Old Award Winning Bastard Technologist
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    Assumintg you have a 88a or 88D analog supply, you have some issues you would have to address before removing the buck/boost. Are you refering to a external transformer in addition to the internal one? If so, maxima mea culpa.

    A beginning note, tube voltage plus the voltage accross the passbank transistors MUST by physics equal rectified line voltage!


    So if you have a 245V line, you have a 155 to 160 V tube, and no buck/boost transformer, that means the passbank sees 80+ volts and goes kaboom, taking out up to 12 expensive transistors in fast pulses and blowing the two passbank driver transistors across the room. The Passbank must see no more then 60V, the green arc on the front panel meter when set to monitor PB voltage. As you turn the current down, the passbank voltage increases, causing more stress. look up transistor SOA (safe operating area) on google. The transistors often fail shorted, and if badly misstapped too high, more then one will fail, causing a overcurrent trip when you press start and possibly blowing a one or more mains fuses internal to the unit, those fuses are 20-40$ each right now, and a high mistap usually takes out a main rectifier diode as well. A low mistap is hard on the cathode and the tube may not obtain full current. Too low a mistap and the tube will not see enough voltage to start.


    Second, the tube cathode tranny is set up so the cathode is at 1150C temperature, 2.8 or so volts and about 25-30 amps. Too cold, and the cathode sags, Too hot, and the cathode blows out and or sputters cathode material into the windows. hence the 3 setting tapswitch on the front panel. The cathode transformer gets its 110V from a internal buck/boost transformer tap,


    HERE ARE YOUR SETTINGS FOR A TYPICAL 88A or 88D SYSTEM
    Your milage may vary as Lexel did make a Euro version, but they are rare and would have similar taps.
    I'd have to drive 575 miles to my friends shop to look up the euro transformer part number, but you can bet its similar.
    ---------------------------------------------------------------

    Buck/Boost Transformer
    Measured Voltage Orange Wire Blue Wire Action
    ------------------------------------------------------
    190-203 VAC TB2-1 TB2-3 Boost
    203-215 VAC TB2-2 TB2-3 Boost
    215-227 VAC TB2-1 TB2-1 Even
    227-238 VAC TB2-2 TB2-1 Buck
    238-245 VAC TB2-3 TB2-1 Buck


    Filament Transformer

    Turn on "Line" circuit breaker. Measure AC voltage between TP5 and TP6 on front panel. SWITCH OFF "Line" circuit breaker before changing switch S10:


    Voltage less than 116 VAC: Set S10 to position "A".
    Voltage between 116 and 126 VAC: Set S10 to position "B".
    Voltage more than 126 VAC: Set S10 to position "C".
    If less than 108 or greater than 135, consult manufacturer.
    Each tube has its own test sheet - use those settings instead if available.

    ----------------------------------------------------------------------------------


    Sorry for the sarcasim, but that internal transformer is there for a reason, I just worked a 12 hour shift, and I'm tired. If you post a picture of the inside of your supply, I will tell you what you have. For higher European line voltages (relative to the US) a external step down may not be a bad idea. If that is the case, and your talking about a external transformer , we can talk (went back and edited this) But the internal one needs to stay and be properly tapped.

    Steve Roberts
    Last edited by mixedgas; 01-28-2008 at 18:48.

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