Initial run - Streamers too short -is there a test I can do?

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Initial run - Streamers too short -is there a test I can do?

Postby brain » Sun Oct 26, 2014 3:34 pm

GOt the unit running, after the following:

  • HCT14 died after accidentally hitting pins 7 and 8 of the *21 driver with the meter probe at the same time, and I think took out the 7805 with it. Replaced with spare 7805 and LS14 (for now, was in the parts box, will order HCT14 from Digikey)
  • HCT74 dragging pin 4 of HCT14 output high. Replaced with Ls74 (again, will order proper part)
  • Initial test gave humming but no sparks. Had to switch the driver ICs to get unit working
So, unit works, but underwhelmingly. streamers are 1 inch long at max PW. My guess is that something is done in (either the drivers or the IGBTs). But, before I go tearing the unit apart, I am wondering if there is a "nominal test setup that will generate best case effects (tying a specific ground plane to something, etc.).

I am leery tearing into the unit, replacing all 4 parts, putting it back together, and having the same effect, and then finding out it's just the lack of a ground plane or something like that. I ask because I pulled out a 4' flourescent tube from the basement, and when I put the tube near the breakout, I get nice large streamers (only about 4 inches, but very wide) with the tube nicely lit. So, it does seem the power is there (the sound level also increases significantly in the process).

Jim
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Re: Initial run - Streamers too short -is there a test I can

Postby Alex » Wed Oct 29, 2014 10:22 am

LS series chips will not work.
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Re: Initial run - Streamers too short -is there a test I can

Postby brain » Tue Nov 18, 2014 12:01 am

Thanks for the update. I purchased HCT replacements, and things are working well now. Unit is currently disassembled getting more coats of poly, as it was arcing a bit.
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Re: Initial run - Streamers too short -is there a test I can

Postby brain » Thu Nov 20, 2014 7:57 pm

No amount of poly fixed the issue, but I did cut a round "shield" out of plexi that I silicone'd to the primary tube, and all is well. I recommend everyone do that, as it's trivial to do, and solves the problem for good, as far as I can tell.

Jim
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Re: Initial run - Streamers too short -is there a test I can

Postby Alex » Thu Nov 20, 2014 10:13 pm

good to hear!
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Re: Initial run - Streamers too short -is there a test I can

Postby brain » Thu Nov 20, 2014 10:23 pm

So, just for clarity, why don't the LS versions work? Too slow? Not enough drive current?
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Re: Initial run - Streamers too short -is there a test I can

Postby Alex » Fri Nov 21, 2014 12:31 pm

it's fast enough but yes I don't think there's enough drive current
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