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Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Here is what it all looked like before it went to hell :)
For spark size reference its a 80mm diameter secondary form.
So this is what happends when you THINK your power bar / extension cord is grounded and you plug in the ground from the secondary.
I have been pushing 1kW into this SSTC, the breakout point tilts and suddenly I see 10 cm streamers from the antenna towards the toroid o_O
I quickly turned off power and checked things visually, looked fine, so powered it up again, no problems, after about 30 seconds at full power the 5A fuse in my variac litteraly vaporises, its 6A breaker trips, my 10A service breaker trips and the apartment went all black, this was before I discovered what was going on in the power bar.
So now I have a destroyed halfbridge, a possible fucked up variac that trips the breakers at new fuse inserted and I feel a bit pissed off :(
The grounding had been arcing to phase and neutral in the power bar
Please let this be a reminder to everyone, double check, double check.
Registered Member #1169
Joined: Wed Dec 12 2007, 09:16AM
Location: Portland OR
Posts: 251
Guh! This happened to me last week when I noticed my secondary grounding to other parts in the coil. So far I have a dead half bridge, toasted variac, and a melted extension cord.
Banned on 3/17/2009. Registered Member #487
Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617
Last week I forgot to reconnect my secondary ground and it arced the bridge and fried one IGBT. Its best to keep the earth ground lines far away from all other things if possible. Last year I designed a board and had a trace for the earth ground and it caused all kinds of problems.
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
The exploded mosfet
Two new mosfets are installed instead of the two that failed and one exploded.
I have scoped the control circuit and got 2.5V square signals out of the 74HC14.
Changed UCC drivers for new ones, signals are fine alternating.
555 is responding beautifully to changes on the potentiometers.
But at the mosfet gates I have a static very noisy sinus like 10 to -10 signal just going and going no matter what the rest of the circuits outputs, the GDT gives a little noise.
74HC14 is the only thing I did not have in spare, but it "might" be fine, its 2.5V squared pulse, I seem to recall it was 5V before the incident with sparking antenna, waiting for new ones from thailand atm.
Registered Member #575
Joined: Sun Mar 11 2007, 04:00AM
Location: Norway
Posts: 263
There absolutely seems something to be wrong with the 7414, the output should be 5 volt. The 7414 has several inverters so maybe some other channels work.
Banned on 3/17/2009. Registered Member #487
Joined: Sun Jul 09 2006, 01:22AM
Location:
Posts: 617
MadsKaizer wrote ...
Here is what it all looked like before it went to hell :)
For spark size reference its a 80mm diameter secondary form.
So this is what happends when you THINK your power bar / extension cord is grounded and you plug in the ground from the secondary.
I have been pushing 1kW into this SSTC, the breakout point tilts and suddenly I see 10 cm streamers from the antenna towards the toroid o_O
I quickly turned off power and checked things visually, looked fine, so powered it up again, no problems, after about 30 seconds at full power the 5A fuse in my variac litteraly vaporises, its 6A breaker trips, my 10A service breaker trips and the apartment went all black, this was before I discovered what was going on in the power bar.
So now I have a destroyed halfbridge, a possible fucked up variac that trips the breakers at new fuse inserted and I feel a bit pissed off :(
The grounding had been arcing to phase and neutral in the power bar
Please let this be a reminder to everyone, double check, double check.
it kinda sounds like you might have GFI breakers in your box that don't like the RF stuff.
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Tom540 wrote ...
it kinda sounds like you might have GFI breakers in your box that don't like the RF stuff.
Funny thing is, the GFI breaker have yet not tripped, its always the 10A breaker, but now I have moved to a seperate 16A service so I no longer kill the entire apartment :)
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Hopefully this does not count as a double post :)
I spend somewhere near 14 days faultfinding this mysterious little creature of a sstc, couple of minutes to hours every day. Every IC have been replaced, carefully scoped all waveforms, new mosfets and everything. But it still refused to even oscillate a tiny bit.
Only until someone on irc suggested me to take a look at my gate resistors, and sure enough, I had a dead 5 ohm resistor laughing at me :/ after a quick change it was working again!
The it was time to build a audio modulation, went with reachings modulator as I love the strikes of sound rather than a CW flame.
So it didn't work at first either, some smoke due to tiny chinese resistors and whatnot :) got all that fixed and its output was suddenly working flawless, but hooking it up to the sstc driver board only made my mosfets explode once again at only 100Vbus. I never quite found out why this happend, but without a drive signal to the UCCs the current on the input was very high (4A+) at only 30VAC in.
Puzzled I spend the whole day scoping everything looking for something that wasn't normal except the signal never seemed to override the 74HC14. This was due to using two seperate supplies for the driver board and audio board.
If anything I have learned that when something is not working, quickly take the scope, put it in the closet and check all the basic simple stuff first :)
I am "unfortunately" in the middle of my final exams, really should be writing on that paper instead of all this funtime stuff :D so more details and such will have to wait another 14 days and ill write a thorough page about my experiences.
Till then, please enjoy a piece of classical beauty
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Here we have a lot of fake extension cords (european plugs) which do not have the Earth internally connected to anything... This has been a shocking experience for me after using it as a HV ground
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Here is some HD footage of a melody medley:
And some more HD footage of the coil behaving strange in interrupted mode, a new case with some actual shielding of the driver circuits hopefully helps out these problems:
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Mini SSTC, the birth, the teenager years and the bursting rock'n'roll mid twenties!
Its best to keep the earth ground lines far away from all other things if possible. Last year I designed a board and had a trace for the earth ground and it caused all kinds of problems.
