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Most spectacular failures

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LAN_403

Dr. Shark

Sun Apr 02 2006, 04:59PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

No clue. I don't think it was overcurrent, since none of the wires melted. Maybe a bad contact caused excessive IÂ²R losses.
The worst thing really is that I fried the scope probe tip, the black mess at the bottom

Electroholic

Sun Apr 02 2006, 05:01PM

Registered Member #191 Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720

looks like a ZVS
treminal strip overheated?
from bad connection

Marko

Sun May 14 2006, 03:58PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Something to revive the old thread (pity it's abandoned!)

I needed to bring my mini SSTC for a showoff (organised by school) and it was supposed to work withut pauses for few hours, and my royer SSTC would probably completly melt during that.

So I built a nice little clas E SSTC with antenna feedback, wich was far more efficient and reliable.

It came out nice, but topload was somewhat crappy (ping-pong ball in foil)

It worked well but sometimes popped a small cloud of smoke from the topload. I tought it is a bad connection under the poliester (but it would 'fix' itself quickly).

I brought it home and realized that ping-pong ball was actually burning, as underside of topload got quite black now.

I foolishly ran the coil like that (and even pimped the topload with a screwdriver).

In a moment plastic ball ignitied, and burst into a cloud of awfully smelling smoke, as very little air could go in trouugh a small hole under.

In panic I managed to throw the ball from the coil, it fell on the table and for about next 10 seconds a jet of dense smoke was emanating from it. It stunk the whole room with terrible smell.

I aslo fried 7815 regulators in the coil, probably with the probe or aligator clip, so coil is completely dead now

The 'spectacular' thing was how flammable the damned plastic is. Ball burned out completely with very little air, I ended with a crispy ball of foil with some char inside!

I cut the crispy topload in half, ball is turned into black stuff shown!
Maybe a way to make formerless toploads...

Dr. Shark

Sun May 14 2006, 05:42PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Yeah right! I was looking for this thread somewhere in the depth of page 7, and now it is here on top!?!

Anyway, this is my submission:

closer look:

I haven't got the slightest clue as to what happened. I was tinkering with my 220V mains driven Half-Bridge, and trying to figure out why I would not even get close to an inch of sparks. OK, I admit I got pretty hot arcs, but with little voltage, and also the primary got smoking hot, but this??? Glad it did not explode!

Marko

Sun May 14 2006, 05:48PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Can you pop it to see what's inside

I wonder if it would be more stinky than my exploding topload SSTC if it blew...

Dr. Shark

Sun May 14 2006, 06:00PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Here you go.
I took the jigsaw and cut it apart to see what had happened:

looks like some local heating took place in the high voltage windings, and also smells like it

Definietely not as bad as your ping-pong ball, though.

Now this really seems to be a tell-tale sign of internal arcing, and not just resistive heating. Really weird, since as you can see from the sparkgap distance in the pic above, no more than 30kV could ever have developed.

Marko

Sun May 14 2006, 06:10PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Looks like it jst lots integrity from melting, and maybe arced over later.

I guess gas developed made the buble, or just molten plastic shaped itself like that..

Dr. Shark

Sun Sept 10 2006, 04:55PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Here's another fun one:

again, if I knew how it happened I'd probably have prevented it... it just burst out in flames when I was messing with my cascade/marx setup, which was spraying ions from the ground return wire, so some HV punchthrogh might have been involved.
All further experiments stalled

PS. on a second thought: the xfmr is still too hot to touch, so it was probably overloaded for a significant amount of time. Why the ZVS driver and Flyback behind it did not even get warm is beyond me.

Avalanche

Sun Sept 10 2006, 06:04PM

Registered Member #103 Joined: Thu Feb 09 2006, 08:16PM
Location: Derby, UK
Posts: 845

Slight MOSFET failure here...

Tesladownunder

Sun Sept 10 2006, 06:49PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

This HV resistor array of 67 x 1.8K 2W resistors was subjected to 100kV but failed.
The burnout below lost only 4 of the 67 resistors. It was resurrected and extended to 100 resistors for total 160 kohm and immersed in oil in the container above. Despite the 6 inch gap between electrodes it still arcs across at times with this 100kv supply.

Peter

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