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johncohn

Sat Mar 12 2011, 07:17PM

Registered Member #1848 Joined: Sat Dec 06 2008, 03:24AM
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Posts: 15

BryanD,
Are you using the bridge as a full wave or a half wave bridge.. I'm pretty sure you want the halfwave. picture your bridge as it's component 4 diodes and wire them the way the discrete diodes would have been wired.. that means you'll only be using 3 of the tabs on the bridge.. not all four.. Get what I mean.. If not.. I can draw it for you.
-jc

johncohn

Sat Mar 12 2011, 07:22PM

Registered Member #1848 Joined: Sat Dec 06 2008, 03:24AM
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Posts: 15

Folks,
Here's an update.. I checked out the advanced modulator.. it's working fine.. I've started to work through the resonator board with a scope . It seems the strike zorched at least U1 (a lowly 74HC14) and U5 the UCCC3731 negative going gate drive. Can anyone see how a primary strike (which is what I assumed happened) .. could take out U1.. or U5.. I can imagine.. I guess that a catastrophic failure of the IGBT's could have sent a nasty HV pulse back through the gate pulse transformer.. but I'm baffled how that would have propagated back trough to U1.. Any clues ?
-jc

BryanD

Sat Mar 12 2011, 07:55PM

Registered Member #3528 Joined: Sun Dec 19 2010, 12:44AM
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Posts: 14

Hey Johncohn,

I tried your recommendation, and everything is working A ok now. Thank you very much! Now on to the rest of the testing :)

BryanD

Tue Mar 15 2011, 11:52PM

Registered Member #3528 Joined: Sun Dec 19 2010, 12:44AM
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Posts: 14

Hello again,

I've ran into a problem with testing the IGBTs, and was wondering how others went about it. I tried measuring the Vge (step 6 on page 90). I tried researching how to do it properly, but came up empty once again. I've connected one probe to the gate of one IGBT and one of the emitter screws of the same IGBT. I left the ground clips of both probes disconnected from everything. I added the two inputs and inverted one. All I get when I do this is a bunch of noise. I also have all the proper inputs, modulator and signal generator. Do you have any idea what I've done wrong here? I seem to have problems with these differential measurements :P

Whats really weird is the first time I measured the first IGBT there was lots of noise but I was able to make out the appropriate signal, and was even able to measure the rise and fall times, which were ok. I moved on to the second IGBT in the same fashion, but got nothing but noise. So I moved back to the first IGBT to see if I can catch the differences, I ended up getting nothing but noise on that IGBT now. Since then I haven't been able to get anything out of either one.

Could it be something wrong with my CT or am I just measuring wrong again?

Thanks in advance,

Bryan

johncohn

Sun Apr 03 2011, 08:45PM

Registered Member #1848 Joined: Sat Dec 06 2008, 03:24AM
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Posts: 15

Just an update.. the primary strike I had seems to have taken nearly out every piece of silicon on y resonator board.. the 74hc14's, the opto-isolator on the HV sense, both gate drivers,.. and it's still not working. I have a mysterious problem with the current feedback circuit.. the signal from the current sense circuit... or the signal generator I'm using for test.. is not propagating completely through the U1 74hc14 hex schmidt trigger.. I have a nice square wave on pins 1.. it's inverse on pins 2 and pin 3, but only a low swing noisy mess pin 4 .. ugh.. I have had to patch many broken tracks caused by desoldering. . my one recommendation to everyone starting their project now is to to SOCKET EVERY CHIP !!!
-jc

UnionTesla

Mon May 02 2011, 01:41PM

Registered Member #2685 Joined: Sun Feb 14 2010, 07:23PM
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Posts: 11

Hi, I am curently constructing the minibrute and was wondering if there was a specific gauge of wire you used for the high current bus labeled in the schematic?

UnionTesla

Mon May 02 2011, 03:39PM

Registered Member #2685 Joined: Sun Feb 14 2010, 07:23PM
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Posts: 11

Hi, I am curently constructing the minibrute and was wondering if there was a specific gauge of wire you used for the high current bus labeled in the schematic?

raysf

Tue May 24 2011, 01:27AM

Registered Member #2845 Joined: Mon May 03 2010, 06:40AM
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Posts: 12

The high current wire wants to be something like 8ga or thicker

rjdel

Tue Jun 28 2011, 03:03AM

Registered Member #2633 Joined: Sun Jan 17 2010, 06:25PM
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Posts: 3

Ok..been away from this project for a while, but I am glad t be back at it.

Mechanical is pretty much done, and electronic in 95% done...just a few things left!

I have a few question about the addendum for the Mini-brute:

1. Item 1 in the REV-A section refers to the manually placed C32 as 10pF, while the schematic and parts list refer to it as a 100pF. ??

2. In the REV-A section, item 4 states that C81 and C82 are correct in the schematic but that they are not on the PCB. My PCB actually does have C82. Just curious if this is a typo in the addendum, or if I am somehow mistaken (very likely!)

thx.

Uspring

Thu Jul 07 2011, 04:17PM

Registered Member #3988 Joined: Thu Jul 07 2011, 03:25PM
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Posts: 711

Hi guys,

I'm new to this forum and recently got my minibrute kit. I've a couple of
questions, you may be able to answer.

1.) I'm using a different secondary, than the one Dan describes. It has the same
diameter but a higher resonant fequency (about 240 kHz). Instead of decreasing
primary inductance, I thought of decreasing primary capacitance by adding a 4th
set of caps in series to the standard 3.
I've done a simulation, which tells me, that for a given current limit, it is better
to decrease capacitance instaed of inductance. Right?

The secondary I want to use has its connecting leads on the inside of the
tube. I was wandering if there might be a problem of discharges inside
the secondary. Can I use some plastic foam or other to avoid this. Anyway I'm
wondering, why the standard minibrute doesn't discharge right down into the
strike rail. That seems to be the shortest way.

2. Instead of threading the primary through the holes of its support,
wouldn't it be easier to make slits?
I'm aware that there might be magnetic forces due to the high current.
IMHO they would tend to lengthen the primary and make it contract so slits,
open to the outside, should work.

Thank you for your thoughts.

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