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Registered Member #2385
Joined: Thu Sept 24 2009, 01:26AM
Location: Waxhaw, North Carolina (Or Charlotte near UNCC)
Posts: 26
Not really sure about this one, but I finally got around to building a fourth plasma speaker using a variation of Tobias' plasma speaker schematic. I had it working beautifully, ≈123kHz ≈50% duty cycle with a wonderful looking arc and very low distortion audio. It was also running nice and cool. This all happened on my first try for this schematic. Well then all things are usually too good to be true.....One week later after not touching it at all - literally hadn't touched it for a week. I go to test it again and well it didn't want to do anything... :( really someone out there has it out for me and every plasma speaker so far has done this to me... I thought maybe the TL494 was acting up or the driver went bad - they both work just fine - thought the diodes went bad ( well that wouldn't really matter much on this design but whatever) turns out they were just fine. Now I think its the Flyback, but when using the traditionally inaccurate method of using a multimeter/ohm meter it seems to be fine. Anyone have any thoughts on what it could be? I could post a video I guess.... but not sure if that would really help
Heres a basic run down of the circuit - if you go to Tobias' website or to my previous post on my last plasma speaker you can get a look at the schematic - you can also check out S m Baker's website which is really good - but If you already have a general map in your head of what it should look like then this should make sense to you
Instead of having a single supply, I have two - one is the supply rail on a bread board that supplies 12v up to 1amp - the other is a 12v power supply that can supply 12v up to 5amps. The lower amperage one is used for the TL494 driver side and the other one is used for the flyback/MOSFET side - the grounds/negative terminals of these supplies are NOT connected together. When I turn the supply on and then connect the positive to the flyback winding the LED on the power supply starts to blink and I get an intermediate spark on the Flayback that looks really weak every time the LED blinks ( Generally this means its trying to draw to much amps - in this case more than 5amps) , I can remove the snubber caps and it does the same thing, so I now the caps aren't to big for it to produce a spark. This is not a case where i had it working for a very long time, its only worked once - the flyback is from my previous plasma speaker tho. The output from the TL494 looks the same as it did when the plasma speaker actually worked, so i'm at a loss here guys.
For the life of me, I can't think of any reason why this thing won't work after working so amazingly well :( It gives me a very big head ache.
Registered Member #2385
Joined: Thu Sept 24 2009, 01:26AM
Location: Waxhaw, North Carolina (Or Charlotte near UNCC)
Posts: 26
Hey thanks for the reply!
I should probably also state that when it did work - By once I meant it worked really well for one day - I might have turned it off and on like 6 times that day and each time it seemed to work just fine - a week later it was a different story - I know very weird right?
Im going to try to use a single supply instead of two separate ones - and also I tried using another flyback, but that was inconclusive since the second flyback was also from a previous plasma speaker so it to could be bad lol. I'm going to provide a link to the schematic so ppl don't have to search for it.
I thought at one point is was the inductive kickback but the components are fine and i have tried multiple spares with the same results - I also thought maybe it was the second winding in the flyback( as in it could be somewhat shorted) :)
heres the link to Tobias' schematic( an older version that doesn't include the Snubber circuit.)
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Some more Plasma Speaker Flyback Problems
