Plasma Speaker issue / High Voltage / Forums

Forums

4hv.org :: Forums :: High Voltage

« Previous topic | Next topic »

Plasma Speaker issue

1 2 next

Move Thread

LAN_403

ZakWolf

Mon Mar 24 2014, 11:30AM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

I built this

a long time ago with great success but eventually broke it... fast forward 2 years, I did some work on it got it to run but the SG3525 gets hot now with 12v in a matter of seconds

What could cause this? how can I lessen or prevent the heating?

Thanks

Antonio

Mon Mar 24 2014, 03:16PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Verify first if the power supply is working, with 12V at the regulator output.
Disconnect the 1 uF capacitor and see if it still gets hot. If it does not, the IC is ok. Disconnect then the primary coil and verify again. If the heating does not occur, the mosfets are ok and something is wrong with the transformer.

Alex M

Mon Mar 24 2014, 03:43PM

Registered Member #3943 Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552

Does the IC still get hot with the gate drive transformer disconnected? I had this problem and it was the gate drive transformer core that wasn't suitable.

Before I swapped the core to a more suitable one I managed to somewhat cure the heating by increasing the number of turns.

ZakWolf

Mon Mar 24 2014, 09:08PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

im using a computer power supply for the 12v, also i think you are right Alex. I had some issues with the old one and changed it out with what i thought would be better i will add more turns and see it that helps.

ZakWolf

Mon Mar 24 2014, 10:52PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

so i had a go at rewinding the GDT with 17 turns now which helped a little but it still gets very hot really quickly. I dont understand because i had a box of ferrite cores of all the same kind just different sizes and i am using the one that worked before like a champ.

I did notice that the voltage regulator (15v regulator) was hot it doesnt have a heat sink but its only passing 12v, could one of my caps around the SG3525 be dead and shoring out cause a high current draw and the chip to short ?

Sigurthr

Tue Mar 25 2014, 01:01AM

Registered Member #4463 Joined: Wed Apr 18 2012, 08:08AM
Location: MI's Upper Peninsula
Posts: 597

A shorted cap on the input of the chip wouldn't cause any power dissipation in the chip, but a shorted cap on the output side of the chip could. I'd check the dc blocking cap on the output side of the chip to see if it went DC short.

Also, having an improper GDT core can certainly cause issues if it saturates. This is why in SSTC use we don't recommend unknown/reclaimed cores.

Alex M

Tue Mar 25 2014, 06:24AM

Registered Member #3943 Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552

Are you using a 15v or 12v regulator? And if its a 15v are you saying that it is only supplying 12v?

What happens if you disconnected the gate drive transformer's primary coil fro the IC all together, if the IC still stays cool with the GDT disconnected then that will certainly be an unsuitable core.

Fair-Rite 5977006401 Type 77 Material is a good choice for a core and at 12v 14 turns of bifilar twisted bell wire gives very nice drive waveforms and the chip only gets slightly warm.

Bifilar means that all of the conductors on the core are twisted together and helps to improve coupling and reduce leakage inductance (bad).

thedatastream has written an awesome guide on winding good GDT's

And so has Uzzors2k

If you just want to get some singing arcs then for now you could try cramming like 30 turns onto your current core, it should cut down on most of the heating but will give not so optimal gate drive.

Regards

ZakWolf

Thu Mar 27 2014, 08:41PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

Hey thanks alex, I still have to try replacing the 1uf cap capacitor its an old one from radio shack and i have a good replacemnt.

Yes im using a 15v regulator because the higher voltage improves the audio, but currently for testing im using 12v.

My windings are bifilar wound and i will try to look for a better core

thanks again

Alex M

Thu Mar 27 2014, 09:03PM

Registered Member #3943 Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552

Cool, let us know how you get on when you do.

ZakWolf wrote ...

Yes im using a 15v regulator because the higher voltage improves the audio, but currently for testing im using 12v.

Really

How much of a difference does it make? I wonder what causes that, a hundred nanoseconds of decreased FET switching time perhaps.

We need the master of flybacks and circuit designer Jan Martis (Dr. Dark Current) to explain that one lol.

Or do you mean 15v instead of 12v to the whole of the circuit including the bridge and transformer?

ZakWolf

Sat Apr 05 2014, 05:33PM

Registered Member #3114 Joined: Sat Aug 14 2010, 08:33AM
Location:
Posts: 608

I will let you know how it turns out I have just been loaded with college :( no time.

I mean I power the "low voltage side" with 15v and the bridge with 45ishVDC produces really nice clean powerful audio with certain flyback.

How come the audio isnt always as good with a homemade FBT vs one from a tv ?

1 2 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob