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Re: [TCML] microbrute DRSSTC
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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