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Help needed with MiniBrute

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StevenCaton

Sun Jan 04 2009, 05:58PM

Registered Member #1845 Joined: Fri Dec 05 2008, 05:38AM
Location: California
Posts: 211

First light!

Thats great to hear! I am actually going to be finishing my mini brute within the next couple of weeks. Good luck with tuning!

d20180

Sun Jan 04 2009, 07:37PM

Registered Member #1828 Joined: Sat Nov 29 2008, 03:00PM
Location:
Posts: 55

Having fun with 6.3A!

HV Enthusiast

Sun Jan 04 2009, 10:32PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

Excellent. Move the break-out point to the edge of the toroid also. I've found that you almost always get better performance in this fashion.

d20180

Sun Jan 04 2009, 11:09PM

Registered Member #1828 Joined: Sat Nov 29 2008, 03:00PM
Location:
Posts: 55

Oh well, it was fun while it lasted. (Then again, I was on my last fuse.) CR51 shorted out to the copper shield. It needs more than 3/16 clearance. What would you recomend as a safe distance for HVSAMPLE or the big caps to ground?

d20180

Thu Jan 08 2009, 11:16AM

Registered Member #1828 Joined: Sat Nov 29 2008, 03:00PM
Location:
Posts: 55

Would it make any difference if I reversed the connections to the primary? (connect the MMC board to the bottom of the primary and the neutral to the top) This would make my wiring a whole lot neater/shorter.

HV Enthusiast

Thu Jan 08 2009, 01:11PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

d20180 wrote ...

Would it make any difference if I reversed the connections to the primary? (connect the MMC board to the bottom of the primary and the neutral to the top) This would make my wiring a whole lot neater/shorter.

You could do that, but you may need to reverse the current transformer polarity. Of course, you'll be checking polarity anyways the first time you power up.

d20180

Sat Jan 10 2009, 12:57PM

Registered Member #1828 Joined: Sat Nov 29 2008, 03:00PM
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Posts: 55

The copper shield and any shielding for the Gate transformer should be earth grounded correct?

d20180

Mon Jan 12 2009, 10:46AM

Registered Member #1828 Joined: Sat Nov 29 2008, 03:00PM
Location:
Posts: 55

Why would CR51 keep blowing? (diode schottky 40v 1A) R126-r124 measure 47k together. Flames are not good. I thought it was arcing to the copper shield so I moved it to the other side of the 1/2 pvc. Now there is a burn mark on the PVC. Any ideas?

HV Enthusiast

Mon Jan 12 2009, 06:46PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

d20180 wrote ...

Why would CR51 keep blowing? (diode schottky 40v 1A) R126-r124 measure 47k together. Flames are not good. I thought it was arcing to the copper shield so I moved it to the other side of the 1/2 pvc. Now there is a burn mark on the PVC. Any ideas?

You probably have CR51 in backwards. Its only a protection diode to clamp the voltage going into the optoisolator.

Or you have the HV+ and HV- installed backwards. Think diode and the current path that will travel with voltage applied across it.

The copper shield doesn't have to be grounded. You can do so for safety if you wish, but its not necessary for proper shielding.

d20180

Thu Jan 15 2009, 12:04AM

Registered Member #1828 Joined: Sat Nov 29 2008, 03:00PM
Location:
Posts: 55

Thanks,

Stupid question session

I just got another beautiful set of boards for the 2nd coil. They came in one piece, how do you normally separate them? (snap, shears, dremel, bandsaw? the set I got 2nd hand were already separated)

How should the Minibrute respond.

PW stronger popping
PRF higher rate
Variac small to long sparks up to ~30-35% then stops

I can up the pw then the OC light comes on, can get it to turn off by upping the prf, to a point then it comes back on.
If I up the PRF 80-95% is when the coil really starts to kick but then the 6.3a fuse evaporates.
Should the OC light come on? I have been trying to set it so it just barely flickers. (U21 pin 2 @ 2.588v)
I shouldn't have to turn it up that high, should I?
I checked the advanced modulator I think it's correct (if I read the scope right it tops out around 275 and 100ms in the correct area on the dial)

I believe that I am messing up or have a messed up IC's when checking them.(u2 is suspect) I went through several U1's (my variable voltage source is a little too variable I accidently sent 20V through the isense twice setting the display(very touchy dial at that load.)

If things don't work right this time around I am going to try replacing all the chips at once.

This weekend I have the right fuses and spare parts.

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