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Thread: Coherent GEM CO2 laser RF cable lengths.

  1. #11
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    Ahh, thanks. I had ran across their site while trying to dig up info on the RF cables.

    Saw a whole thread there about Bell laser and Evergreen mixed in. Is evergreen no good anymore? I seem to remember them being the go-to guys for getting tubes redone.

  2. #12
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    I had a quote from photovac -- for my 100w they said $500 just for eval, and then typically $6500 for a refurb. It was years ago but I got a quote from Bell Laser for $1500 and there is the guy in Connecticut on ebay who says $1000 for a 100w gem.

    Have any of you use these vendors? The price from photovac seems especially egregious, I think coherent would do it for less that that

  3. #13
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    Coherent has stopped supporting these lasers so that means whoever can service them can pretty much charge whatever they want. And do so. I talked to coherent through work last week trying to get a manual for this specific model I have and they don't even have manuals anymore.

    The guy in CT is Evergreen Laser which has been refilling laser tubes of different types for decades now. Found on forums where people have sent in their GEM heads to be refilled and had great luck. Others no so much. So I am a little confused to what's going on with that.

  4. #14
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    If itís a match issue try a 2M ham tuner. 600w 100mhz what rms peak to peak? Make sure the tuner can handle the load. Might be easier to roll your own. Can you drive the load through the cable to a dummy load? Put a Bryd watt meter in like and measure the reflected and forward power. If it looks good repeat with the actual load. If the reflected in low your cable is good. Trim as needed.

  5. #15
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    I was looking at a laser for a COVID emergency project. . Before I shot my mouth off and recommended a purchase I'd regret, I went down to look at Photovac. Only an hour and a half from here. Like, I said, suitably impressed by the care, quality, and testing. Not to mention the PhD who perfected the RF Co2 was the owner's friend and mentor. SYNRAD sales sent me to Photovac for a used laser. THAT speaks volumes.

    Turns out die cutting slices large clear plastic sheets far faster then 250 Watt lasers on gantries. I needed a real high quality laser to replace the very short lived Chinese dual tube system. Sale didn't happen in the end as die cutting the plastic was just as precise and beaucoup faster.
    If we went with laser I would have bought from Photovac in a heartbeat.

    As for Evergreen,

    Real easy, ask if the Fostini family ((Spelling? Old Memory!)) still own Evergreen.



    Steve
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  6. #16
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    Interesting, I got this 100w tube for a song to I might give a try with evergreen since worst case is I need to start fresh with another surplus tube. The 30w synrad in my laser cutter is down to about 7w after it warms up so I need to figure something to pretty soon

    Also - macona I have a bird 8230 load (2500w -- requires water cooling for extended operation above 200w but for testing it will do fine on air at 1000w for a few minutes) if you are interested to borrow it. I believe you were in the US somewhere?

  7. #17
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    Quote Originally Posted by krazer View Post
    Interesting, I got this 100w tube for a song to I might give a try with evergreen since worst case is I need to start fresh with another surplus tube. The 30w synrad in my laser cutter is down to about 7w after it warms up so I need to figure something to pretty soon

    Also - macona I have a bird 8230 load (2500w -- requires water cooling for extended operation above 200w but for testing it will do fine on air at 1000w for a few minutes) if you are interested to borrow it. I believe you were in the US somewhere?
    I have a friend at PSU that has a 1500W load and another buy offered to give me what looks like a military version of the old cantenna that I can have so I think I am good to go. Thanks for offering though!

    I talked to a guy at work, we integrate much bigger Coherent Diamonds in the PCB machines we sell, and he said they can have diffusion issues if the heads are old.

    I am going to get a chunk of LMR-400 which is what I believe is the speced cable for the head and make up one more cable to double check. The power supply does show forward and reflected energy but thing thing is that if the power supply detects a mismatch it kills the power, so it's hard to tell whats going on.

  8. #18
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    I remembered we had an old Coherent Gem-Q600 at work, it's an old 60w q-switched CO2. Yeah, weird...

    Anyway it is also excited at 100MHz so I measured the length and it came to exactly 4.6 meters just like the chart so I am ordering some more wire and ends and going to give the cable a second try. Ill just make it half length.

  9. #19
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    What ever you do have a written agreement, I've heard of too many Co2's perpetually disappearing during rebuild / shipping.,

    Steve
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  10. #20
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    Hmm, thats odd.

    Well, i sent them a message through email and ebay monday and i have yet to get a reply. We'll see what happens.

    I got the RF dummy load, waiting for mineral oil to show up to fill it. It's a variant of the old cantenna.

    -Jerry

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