If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Jamie Cansdale wrote ...
Xray wrote ...
Your flyback probably won't work now that you've shorted out those windings. By doing so, you've created a direct short dircuit across those windings which would prevent the transformer from producing high voltage. It will likely draw a lot of current from your ZVS driver and damage the FETs.
If you are getting corona or arcing on those extra terminals, try to insulate them by covering them with heat-shrink tubing, and then coat them with a thick layer of Silicone. Wait until the Silicone is completely dry before powering your ZVS up again.
That's what I thought initially as well. I'm now wondering whether the sparking was actually due to capacitive coupling and not because the terminals were taps of the high voltage winding. The other terminals are maybe for the original primary winding, the CRT heater and other voltages the monitor it came from needed. I wonder if it's better to have these all tied together, rather than having charge that isn't being used moving around inside the transformer?
If the charge isnt used then its not really moving. Being present and flowing are two different situations.
I think your making this way to complicated, first undo the dead shorts youve soldered on the horseshoe. then try to find the pin the fat HV wire arcs to most vigorously, that pin will be the secondary return for the secondary. (im thinking youve chosen thewrong pin for the ground)
Most people dont have the problems your describing, so im suspicious of your setup.
Registered Member #3904
Joined: Sat May 21 2011, 10:32AM
Location:
Posts: 28
Patrick wrote ...
Most people dont have the problems your describing, so im suspicious of your setup.
I'm just experimenting with an old, half dead flyback, trying different things to see what happens. I've had it spewing corona with a 555 and arcing with a with a ZVS in the past, so this time I wanted to try something else. ;)
I wondered what would happen if I treated the primary like the primary of a tesla coil (with a spark gap and a few bottle capacitors). To my surprise it worked and there were sparks between the high voltage terminals. As I moved the terminals apart, the terminals at the bottom started sparking. This is when I soldered all the terminals at the bottom together to see what would happen. In this configuration I started getting 1 inch sparks (not arcs) across the high voltage terminals. The sparks were so loud, I thought they might be capacitive discharges, but in hindsight I guess 1 inch sparks are just loud. :)
I've since hooked the flyback up to my function generator and high voltage probe to see what's happening. I set the function generator to a 300kHz, 15V sine wave (its resonant frequency). The function generator has an output impedance of 50ohms, so there's very little power here. With the pins at the bottom all shorted I was seeing only a few volts on the scope. When I desoldered the pins, it was suddenly off the scale when using a x1000 probe! (see attached)
When the function generator is set to 10V, there is nothing on the scope, but at ~15V, spikes of 50kV suddenly appear! The frequency of the spikes increase with the voltage, but at 15V they're appearing at 2.5kHz. Can anyone explain what is happening here?
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Jamie Cansdale wrote ...
I've since hooked the flyback up to my function generator and high voltage probe to see what's happening. I set the function generator to a 300kHz, 15V sine wave (its resonant frequency). The function generator has an output impedance of 50ohms, so there's very little power here. With the pins at the bottom all shorted I was seeing only a few volts on the scope. When I desoldered the pins, it was suddenly off the scale when using a x1000 probe! (see attached)
When the function generator is set to 10V, there is nothing on the scope, but at ~15V, spikes of 50kV suddenly appear! The frequency of the spikes increase with the voltage, but at 15V they're appearing at 2.5kHz. Can anyone explain what is happening here?
You might be seeing LC or RC time constant behavior here. Not sure i fully understand your setup though, and 300kHz is pretty high for the typical flyback, so you might be seeing unusual results from that alone. If your resonating the secondary i guess you could be getting very high pulses in the 50-60kv range, this is not typical though.
what is the HV probe your using? is that the HP 34111A one? Do you know what the internals are on the high bandwidth probes like that one?
Registered Member #3904
Joined: Sat May 21 2011, 10:32AM
Location:
Posts: 28
Patrick wrote ...
You might be seeing LC or RC time constant behavior here. Not sure i fully understand your setup though, and 300kHz is pretty high for the typical flyback, so you might be seeing unusual results from that alone.
300kHz is high, but it's consistent for this particular flyback. In the past it behaved like a typical flyback, but something has now changed.
Patrick wrote ...
If your resonating the secondary i guess you could be getting very high pulses in the 50-60kv range, this is not typical though.
I've used this exact setup plenty of times in the past to find the resonant frequency of various flybacks, but I've never seen this behavior before!
Patrick wrote ...
what is the HV probe your using? is that the HP 34111A one? Do you know what the internals are on the high bandwidth probes like that one?
I'm using one of these (which is only rated for a 30kV pulse). I wasn't expecting such a high voltage to appear!
Registered Member #3904
Joined: Sat May 21 2011, 10:32AM
Location:
Posts: 28
I've attached what the trace looks like with a known good flyback. This one has a resonant frequency of 340kHz (I think monitor flybacks tend to have a higher frequency than TVs). You can see a nice consistent sine wave going from 1.65kV to 1.73kV.
I then attached a bottle capacitor between between the high voltage terminals of the flyback with the strange spikes. I was curious to see whether the diodes were still working and it would hold its charge. When I connected this one up with the capacitor attached, the waveform suddenly looked very much like the known good flyback (see attached).
It looks like there is an open connection where the flyback's capacitor once was. I'm still not sure how to explain the spikes that appear at a much lower frequency than the input waveform. Do you think this will be something to do with the diode's voltage drop?
Registered Member #3904
Joined: Sat May 21 2011, 10:32AM
Location:
Posts: 28
I think it must be the flyback's capacitor that's on the blink. It has mysteriously started behaving like a normal flyback again. Maybe the spikes were caused by it sparking inside the capacitor?
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Jamie Cansdale wrote ...
I think it must be the flyback's capacitor that's on the blink. It has mysteriously started behaving like a normal flyback again. Maybe the spikes were caused by it sparking inside the capacitor?
Now that would expalin alot! I was wondering what could what we see in those screen caps.
Registered Member #3904
Joined: Sat May 21 2011, 10:32AM
Location:
Posts: 28
Patrick wrote ...
Now that would expalin alot! I was wondering what could we see in those screen caps.
It appears the problem was actually with my HV scope probe. When I looked at another flyback, I started seeing exactly the same spikes. I then looked at the output from a NST and they were there again. :(
Can anyone recommend a HV scope probe that won't break the bank? The HVP-15HF probe I have wasn't exactly cheap, but name brand HV probes all seem terribly expensive. I'd been happy with the HVP-15HF up until now and I wouldn't want to be without one!
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Dangerous ZVS Driver 'floating' at 30kV+ ungrounded - Safety advice please!
