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Thread: Experimentonomen´s first argon.

  1. #11
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    diachi, yes, but you need to dissipate 500 watts or so on the heatsink, maybe more.

    Steve
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    Sound like i need to buy more parts, a 50-90V 5W zener, some 1ohm 250W resistors, sheesh screw it im better of just buying a psu.

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    You can dispense with the 1 ohm resistors...
    It just makes life a little easier (10% less dissapation) on the fets.

    The SP tubes are close enough to a uniphase to hack a uniphase head for the wiring and ignitor.
    Perhaps my tone of writing is too negitive.

    Why screw it??, anybody can hook up a box...... few can say they have built their own psu.

    Steve
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    Your not negative, i just thought i could simplify things alittle, tho im gonna skip the digital and light mode part.

    Heres a revised schematic, lets see if i got it right this time:

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    [QUOTE=Experimentonomen;132020]Your not negative, i just thought i could simplify things alittle, tho im gonna skip the digital and light mode part.

    Heres a revised schematic, lets see if i got it right this time:


    Thats a lot better, you can ditch the 11RA 90 for something a bit less expensive, mouser sells VISHAY parts for about 5$ that are similar but a lot less expensive. . Idea is having a whopping huge die in a metal package for a uniform field. ie a 400V 40 amp or something like that in the metal can/ screw stud based parts.

    I think your ready to get started. While not always first quality, usually electronic goldmine has nice cheap surplus TO-247 fets. The most expensive thing will be the silpads, but you can get those on the bay.

    Oh and about a 4"piece of plastic rod to keep your finger off the ignite switch. My ignitors use the cheap gas gap 96 cent telecom protector things that fire at 250V. Then I switch the boost supply. Makes fingers and switches last longer. If I need to, two in series works. Oh and the zener goes from source to drain on the fets. Some designs have it so when it fires, it pulls the gates high even if the OPAMP is off, but that is a lot of work.

    The two transistor schmidt trigger on the lexel 88 PSU diagram at the FAQ is easily adaptable , that might be a future overcurrent shutdown.

    I'd say find a surplus suitable AL plate with fins and your good 2 go.
    Steve
    Last edited by mixedgas; 01-14-2010 at 13:00.
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    I have a whole sheet of silpad material I also got some proper heatsinks. I also have a whole tubes of them IRFP450´s, tho i only have some 15V zeners that i dont remember if they are 1W or 5W but i could string 4-5 of those in series to make a temporary 60V zener until i´ve got a real one, i´ll also add the 1ohm 250W resistor when i´ve gotten one of those.

    My ignitor wont have a switch like that as it really is one of these: http://cgi.ebay.com/ws/eBayISAPI.dll...=STRK:MEWNX:IT

    How that zener is supposed to go is bugging me a bit, in the bjt passbanks it between the collectors of the main transistors and base of the driver transistor and it has that 100ohm resistor in series with it.

    I have also thought about using a large heavy heatsink i have with four 2N3716´s on it, using a 2N3019 as the driver transistor.

  7. #17
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    Quote Originally Posted by Experimentonomen View Post
    Your not negative, i just thought i could simplify things alittle, tho im gonna skip the digital and light mode part.

    Heres a revised schematic, lets see if i got it right this time:
    Hi, you could try also my simple PSU, I developed for the same Spectra Phisics argon tube.

    http://www.repairfaq.org/sam/laserasc.htm#ascmc1

    Regards
    Mario

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    Thats basically what i had before the discussion with mixedgas.

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    I feel stupid for asking this but i have never dealt with argon psus before.

    This question is to mixedgas, would these for for that zener to protect the pass bank ? And how about i put one between drain and source of each fet, or should put one between all drains and gates with a 100ohm resistor in series or should i just do it like in the last schematic ?
    http://cgi.ebay.com/10-P6KE75A-75-V-...item22f969cfb7

    And for the blocking diode i plan to use one or two of these instead of that 1N1190 because i have two i front of me as i type this and i also have the proper heatsinks they screw into:
    http://pdf1.alldatasheet.com/datashe.../SKN20/12.html
    Last edited by Experimentonomen; 01-15-2010 at 11:14.

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    The work continues:






    The day i finished the box, i got an offer for a whole SP-161B laser head minus the tube and fan for only 150AUD including shipping, so i only add my tube and a suitable fan, this leads to the yellow box getting ditched, yep you heard right, despite beeing 3 days wasted i rather have a genuine SP161B head than some ugly diy.

    Today i started working on the psu, first up is the linear passbank.

    The heatsink, probably way undersize but i´ll try it and see, i´ll just put a stronger fan on it if it overheats:



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