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Re: [TCML] microbrute DRSSTC

On 1/1/2013 2:53 PM, Joe Mastroianni wrote:

Hi Alton,
Ok, well, then it if all that is ok then it sounds like you may need to work on the tuning.  You will need to wind or unwind the primary coil wire to see if when you get a breakout arc.  What I do is I turn up the variac slowly.  If the coil is tuned, by the time you get to 25V output on the variac you'll see at least a little breakout on your breakout point.   Pay attention to the sound of the arc.  If it "sputters" (you'll know it when you hear it) you are not tuned correctly.  That sputtering sound is badness.  If you don't correct it you will eventually blow up the IGBTs, so keep the voltage low until you correct it by tweaking the tuning.

What I wound up doing was to wind or unwind the primary helix by 1/4 turn increments, using heavy tape to secure the primary coil wire in each position.  Other than using an oscilloscope and signal generator there's really no great way to check the tuning other than turning up the Variac moderately and listening for breakout.  If you don't get a breakout arc, then turn off the power, adjust the coil by 1/4 a turn, and try again.  Once you do see a breakout arc you might have to wind as much as another 1/2 or 1/4 a turn in or out to get it right.  It's a trial and error process that takes some time.

The other possibility is that you need to reverse the way the primary wire is going through the current sense transformer on the board.  That is, if you have the wire threaded from the direction of the center of the board, through the CT, to the outer board edge, you may have to take the wire out of the CT, and then put it through from the outer board edge inward toward the center of the board.  Nothing is going to work if the current sense direction is reversed.  Unfortunately, it's hard to tell apriori which way is going to be best (it depends on which direction you wound your coils), but it's easy to switch.  But it's a digital thing - it will either work or not. There's no "almost" with that, like there is with tuning.

Happy new year and hope you get it working.

Cheers,
Joe


On Jan 1, 2013, at 11:55 AM, W5als wrote:


Hi joe
     Yes the buzzing is there just like it should and yes the controller has a pulse coming,
I also try another controller to. I check the IGBT's and did not find one shorted
I will check them again. If they short it should blow the fuze. The over current light
Come on when I the controller up to 80% because R23 is set at .7 volt. I also have
the break out point on it. I also try using the varic today it still doesn't work.
I have some detail picture if someone want to look and see if I did something wrong.
Email me direct and I can send them to you. Thanks for all the help.
Alton

Sent from my iPad

On Dec 31, 2012, at 5:46 PM, Joe Mastroianni <joe@xxxxxxxxxxxxxx> wrote:


Hi Alton
I have successfully built one of those MicroBrutes.  Mine works fine.  I have blown up a whole lot of IGBTs, though, messing around with it.  But that's my fault.  I'm sure Dan will help you out when he gets back from the holidays, but maybe this will help.

- Before you apply any voltage at all to the tank circuit via your variac (you are using some kind of variable power supply to the tank, presumably - this is of course separate from the power supply for the control circuitry) turn on the control circuitry (you'll see the blue LED light up) and then turn on your interrupter.  With no power at all to the tank - you should hear a very high pitched and faint, sharp, buzzing sound. The sound will oscillate in time with the interrupter, so if you vary the interrupter frequency or pulse width, the faint buzzing will change, too.

- if you hear no buzzing, nothing is going to work so don't bother applying the tank voltage.

- the Overcurrent LED should not be on (I think you said it was).  If this is on, and you've adjusted it properly (set it very low in the beginning) then something is amiss in the overcurrent latch and you should check that out.  If you can adjust the variable resistor to get it to turn off, that would be a good idea....

- if the overcurrent is NOT on, and there is no tank voltage, and the control supply is on, and the interrupter is on (and you've checked the interrupter output to make sure you have some sort of actual pulse coming out), and you STILL don't hear the buzzing, then I would check the IGBTs.  Dismount them and measure the impedance across the terminals.  If the IGBTs are blown there'll be a dead short between any pair of terminals.  Frequently, just one will be blown.  You have to check both.  If not...well, then it's somethingelse.

- I have found the sequence I have to use to get it to work (actually, the same sequence for any DRSSTC) is - turn on the control voltage.  Turn on the interrupter.  Then slowly increase the tank voltage via a variac.  See if anything happens.  If you just slam on the tank voltage by plugging it in to a 115V outlet, you are liable to blow up an IGBT unless your coil is perfectly, absolutely wonderfully tuned.

- I find I can get 1' to 1.5' arcs from the MicroBrute with only 70V input when things are tuned well.  Tuning includes worrying about what's around the coil.  If you run the coil on your workbench with loads of metal stuff close by, the tuning will be affected.

- You need to use a breakout point.  In the beginning I just rested a small nail on the toroid.  Later I made something better but it's easiest just to get something pointy on there to form an arc.  Though be careful - you only want ONE pointy thing.  If you have multiple pointy things, like if you didn't put the tape on smoothly enough, it will try to break out from all those places and you won't get any big arc, just a whole lot of tiny ones.

Hope some of this is useful

Joe


On Dec 31, 2012, at 2:42 PM, W5als wrote:


Hi Tom
   Thanks that may help me out will call him Wednesday.
Thanks
Happy New Year to all
Alton

Sent from my iPad

On Dec 31, 2012, at 1:58 PM, CanalRay@xxxxxxx wrote:


Alton: Here is a direct dial to eastern voltage research from Dan
McCauley's current business card. Hope this helps. 1-856-599-8375.

Good luck,

Tom


In a message dated 12/28/2012 10:51:00 A.M. Eastern Standard Time,
w5als@xxxxxxxxx writes:

Hi
I am building a microbrute drsstc by  eastern voltage research and
i am have problems
and need some help. I  finish it yesterday and was trying to fire it off
and got nothing so  by
the book i reverse the polarity through the current transformer that
didn't work.
All the voltages are right check them 3 times the LED's  light up, the
over current led come
on when I ramp the PW control up. I  took the board out check all solder
joints and check
ever IC twice to  make sure it was right. I tested ever diode and they
were good, ever  cap.
was check twice, I ever check the controller and wave from twice, i  even
compare the wave form
to another controller i have. I even ohm the  primary and secondary out
they were good.
Unless the IGBT are open i  don't know what else it could be. Also no
blown fuses neither.
I am not  the best at this but i did have a radio/TV repair shot for 27
years so  this isn't new
to me. I can send detail pictures if someone can compare to  there's. I
will thank anyone
for the  help
thanks
alton
W5ALS
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HI Joe
I have reverse the wire through the current transformer did not help. the one strange thing is on the 5amp fuse side it pull no current at all through my variac with a current meter on it. I have also tried tuning it too never pull current or get a arc. I still think something in or around 
the IGBT's is just not right.
alton
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