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Plasmasonic II build

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Herr Zapp

Fri Sept 25 2009, 04:24PM

Registered Member #480 Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644

Indiana -

I was just scrolling through this thread, and noticed a possible discrepancy in your secondary data. I have no idea if this has any bearing on your functional problems, but I thought I'd bring it to your attention.

In your post of Aug 6, you provided some details of your secondary: 18.25" length, #26 AWG wire, and approximately 1400 turns. The turns count appears to be about 25% too high. The calculated turns count for 18.25" winding length of #26 AWG is closer to 1050 turns. The difference between 1050 and 1400 turns is pretty significant as far as resonant frequency.

Regards,
Herr Zapp

indiana

Fri Sept 25 2009, 05:12PM

Registered Member #2009 Joined: Tue Mar 03 2009, 07:07PM
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Posts: 43

Dr.- No, there is not a fan on the gate drivers themselves. However, I do have 4 fans in the box. There is a good amount of airflow over them, but still right now they get burn you hot after about 20 seconds.

I just wonder what on earth happened to them. They were working fine before with no heating issues at all, and now this.

Do you think the ramping on the waveform is due to a blown IC?

I'll replace the IC's and then maybe heatsink the new ones.

Herr Zapp- The 1400 turns is an approximation. I counted the number of turns in an inch and multiplied (after I lost count in a tangle match. ;)) However, I've not calculated the resonant frequency mathematically. I ran a signal from a function generator through it and monitored it with an oscope to find the resonant frequency.

I feel very confident that my resonant frequency is in the correct ballpark. Also, I tuned it up before I built the new primary coil form and found that the starting frequency was close enough to light a neon bulb. I then tuned it in until I got the highest spark output.

Thank you for looking into that tho. After all that's gone into it I just want it to work!

indiana

Fri Oct 02 2009, 02:33AM

Registered Member #2009 Joined: Tue Mar 03 2009, 07:07PM
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Posts: 43

I poked around and finally figured out what the culprit was.

The new cap that I put in there to lower the frequency range was a dud. One of the leads was broken ... pretty sure I didn't do anything that would have broken it... Then again who knows?

It must have been arcing somehow, and it was making it kick out a frequency up around 800 kHz. That's why the drivers were heating up.

Discovered this after I replaced the drivers of course... new ones were heating up as well.

So, I replaced the cap, and now it's sending a proper signal.

I put some music through it, and could see the modulation clearly on the scope. I turned the cd player all the way up, turned the gain all the way up, but still it wouldn't go into the red at all. Just barely lit up the last green LED.

I put a toroid on top as well as a loop of wire, and when I tune it and turn it up I get a great corona off it, with lots of hiss and little streamers jumping off about 5 per second...

And music so quiet you can't even hear it over the fans. AuGh!

What could be wrong here?

I tune through the bias, and there's a narrow band in the middle of the possible adjustment range where there's static, and just before the static a place where the music is the "loudest" which is still practically drowned out by the hiss of the corona. Other than that, there's nowhere in the adjustment range where you can hear the music at all.

Watched Dan's video again, and the amount of volume he's getting at the same LED meter range is hundreds of times louder than mine at the same LED indication.

The area where you can hear it is right around the 25% duty cycle with no signal, 50% with range. Maybe a little above that.

I've also coupled the coils more closely, and dammit it just seems like it should work. dammit.

EDIT: just checking over everything with a fine tooth comb and I found something...

In note 1 on page 2 of the schematic it says to leave c21 open. However, in the schematic c21 is a 10uf cap and it's c23 that says "see note". Right now, as per the note I have it open. And, I have no more of those caps on hand. Tomorrow I'll go and get one, but could that be causing the problems? What is the purpose of that cap?

HV Enthusiast

Fri Oct 02 2009, 10:09AM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

wrote ...

And music so quiet you can't even hear it over the fans. AuGh!

What could be wrong here?

Tuning is off. You need to retune everytime you use the coil. Also, are you using the big loop for discharge, or just a piece of wire. The more surface area you have, the louder as well.

wrote ...

I tune through the bias, and there's a narrow band in the middle of the possible adjustment range where there's static, and just before the static a place where the music is the "loudest" which is still practically drowned out by the hiss of the corona. Other than that, there's nowhere in the adjustment range where you can hear the music at all.

You have to adjust your bias and tuning to get the right combination. Mostly trial and error. The instructions should give you a good idea of what to do.

wrote ...

Watched Dan's video again, and the amount of volume he's getting at the same LED meter range is hundreds of times louder than mine at the same LED indication.

LEDs don't mean anything. You tune the sensitivity of the LEDs to the particular source you are tuned too. They aren't absolute. They are relative to your reference level you set.

wrote ...

The area where you can hear it is right around the 25% duty cycle with no signal, 50% with range. Maybe a little above that.

I've also coupled the coils more closely, and dammit it just seems like it should work. dammit.

You just need to work on tuning and setting your bias point. Also, try different audio sources as well. Your CD player could be very low output.

wrote ...

In note 1 on page 2 of the schematic it says to leave c21 open. However, in the schematic c21 is a 10uf cap and it's c23 that says "see note". Right now, as per the note I have it open. And, I have no more of those caps on hand. Tomorrow I'll go and get one, but could that be causing the problems? What is the purpose of that cap?

Follow the notes on the schematic. They are most accurate.

Before you worry about audio, your output arc should be quite big and bushy at full power. For example, your electrode consists of a solid piece of wire 15 inches high off the toroid (center). Then attach a 12" piece of fine strand wire to the end of this 15 inch solid rigid wire. With full power supplied, most of that 12" fine wire should be full of corona and swinging around like crazy. If you aren't getting this, then you need to go back and look at your circuit.

indiana

Fri Oct 02 2009, 05:36PM

Registered Member #2009 Joined: Tue Mar 03 2009, 07:07PM
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Posts: 43

During these tests I tuned it perfectly using the same methods I've outlined in earlier posts. Taking into account the new toroid, and the discharge loop which looks very similar to the one in your videos.

I had set the tuning of the coil to maximum spark output, then played through the entire range of the bias without any good effect. Should the coil not be in perfect resonance? The only combination I have not tried is taking the coil off perfect resonance and then tinkering with the bias.

I've tried 3 different cd players now.

Follow the notes on the schematic? I've mentioned before that there's at least one error in the notes, and you said then to go with the schematic. Are you certain that the 10uf cap should not be there? If in the notes you mean cap 23, which is the same type of error as the other one, c21 should be there.

What is the purpose of that cap?

My output arc is quite big and bushy at full power. It looks like the output on your video.

The only thing that's not there is the music.

I just read this over, and it sounds a bit terse. Not how it's meant to come off. I'm happy to do whatever it takes to get it to work, and I appreciate the help. I'm just trying to figure it out.

EDIT: Are there particular cd players that you have used and you know to work?

HV Enthusiast

Fri Oct 02 2009, 06:40PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
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Posts: 3068

If the output arc is there, but the music isn't, then you do have the coil biased properly, or don't have the levels from the CD player set properly.

If your arc is really big, then i'm guessing your bias is set too high and there is "no room" for it left to modulate properly, so you really aren't hearing anything. In this case, you would lower the bias a bit.

indiana

Fri Oct 02 2009, 06:52PM

Registered Member #2009 Joined: Tue Mar 03 2009, 07:07PM
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Posts: 43

1) is there a cd player you know to work? I'm having a hard time searching cd players based on their output voltage. Right now I'm just researching which one is "loudest".

2) what is the purpose of the capacitor across the audio input? there is a .1uf, and a 10uf. In the notes you say leave the 10uf off. In the schematic it's on, and a different capacitor (the high end roll off cap) is noted to be left off. should the 10uf be there or not?

3) I've tried the entire range of the bias with no good effect. the cd player is turned all the way up. When I measure the cd player signal with the oscope the signal is only positive, and it peaks at about 1V.

indiana

Fri Oct 02 2009, 10:23PM

Registered Member #2009 Joined: Tue Mar 03 2009, 07:07PM
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Turns out it's really difficult to find a cd player made now that has a 2V output.

All of the companies are putting out avls circuits that limit the volume. Makes for inferior sound quality, and not as high a voltage output.

I don't know if that's the case for the cd players I have right now, but it's making it tough to find a cd player that's up to the task. ipods certainly won't do it.

Might be the case that a preamp is necessary after all.

EDIT: oops, sorry about the double posts there.

EDIT 2: Well, I have great news, and not so great news... I found another cd player, and started playing with the tuning. It turns out that you actually DO have to come off perfect resonance a bit to get the sound quality to improve. I found the best sounding spot on the bias adjustment (which was very quiet at full resonance) and then tinkered with the frequency until it sounded sweet.

At first I tried it with the 10uf capacitor in line (u21) it was working fine, the sound quality wasn't as good as on dan's vids, but definitely decent. much better than before. still sounded static-y, but overall pretty clear.

Then I removed the 10uf cap, and the sound did actually seem to improve a touch, but only for about 3 seconds before something went POP, and there was a flash somewhere, seemed like it came from the big capacitor. It blew the fuse on my variac. So, I replaced that, but when i went to try it again, the dial of the variac it "stuck" and made a smoking smell. Which caused me to turn it off immediately, of course. I checked all through the connections, and everything LOOKS to be ok. Checked the fuse on the variac again, and it's not blown the fuse...

And when I turned it up it should have gotten high enough to light the fluorescent bulb... but no action on the coil.

So, I checked the variac with a light bulb, works great. Disconnected the cap and did a resistance test on it, the cap starts at zero ohm and slowly builds a charge from the VOM. So, at first glance it seems like the big cap is ok.

Then I touched the two wires which run between the bridge rectifier and the board positive and negative feed, and they show a dead short.

I'm still getting a clean signal at the test points before the gate, so the ic's are all right...

Have I blown a fet? or the bridge? What would have made it blow like that?

I'm thinking to myself though, I pulled that cap out without turning it off first... I wonder if i gave it a little static shock in the process? In retrospect seems like a pretty obviously bad idea. I wanted to hear in real time how it would affect the sound quality.... maybe should have thought about that one a second longer.

EDIT 3: All right, found the culprit. A blown bridge rectifier. Now off to buy a new one...

EDIT 4: Man you guys really getting the play by play now. :) Put in the new bridge rectifier, only to discover that something still wrong. Took the board apart and followed my nose to the burning smell. :) Which arose stinkingly from the two blown mosfets. Have two new ones on order now.

quinn

Thu Nov 05 2009, 12:53PM

Registered Member #2460 Joined: Thu Nov 05 2009, 12:18PM
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Posts: 6

Hi all,first i am sorry for my english is very poor .I am a rookie in Musical Tesla Coil.I just try to build the same plasmasonic II board and want to perform the push-pull mode,but i have a question that how can i adjust the duty cycle to 25% with no signal input?I adjust R24 but i saw the width of the pulse from the gates never changed on oscilloscope,is this right?and without audio signal input it just look the same as indiana's photo above,when i connent the cd, the gates' waveform on oscilloscope was still the same,is this right?

And where should the Pin3 of TL494 be connected to?

HV Enthusiast

Thu Nov 05 2009, 07:28PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

quinn wrote ...

Hi all,first i am sorry for my english is very poor .I am a rookie in Musical Tesla Coil.I just try to build the same plasmasonic II board and want to perform the push-pull mode,but i have a question that how can i adjust the duty cycle to 25% with no signal input?I adjust R24 but i saw the width of the pulse from the gates never changed on oscilloscope,is this right?and without audio signal input it just look the same as indiana's photo above,when i connent the cd, the gates' waveform on oscilloscope was still the same,is this right?

And where should the Pin3 of TL494 be connected to?

pin 3 isn't used.
With no signal applied, your coil will still oscillate and signals will be output from the tl494. the duty cycle should be about 25%.

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