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
Ash Small wrote ...
Patrick wrote ...
.Yes I thought of that too!!! but ill use the denatured pint from the hardware store from what my college professors say, its about 10% water, 10% methyl alcohol (to prevent drinking, tax evasion), then 80% ethyl alcohol. This should be cheaper then drinkable alcohol.
You'll go blind
ArE you in fear i ell DRink It ! oOps ToO latee....
Registered Member #480
Joined: Thu Jul 06 2006, 07:08PM
Location: North America
Posts: 644
Patrick -
Although the trend these days in the surface-mount PCBA assembly world is to use a totally "no clean" solder reflow process, for boards that do get cleaned an aqueous cleaning process is almost universally used. After passing through a cleaning machine where the board is sprayed with multiple jets of hot water (with added saponifier) from all angles, it passes through several rinsing stages using very pure (high resistivity) deionized water.
I think a thorough scrubbing with a new, soft nylon bristle paint brush with warm mild household detergent/water solution, followed by a thorough rinse with warm distilled water, should remove all your fingerprint residue.
Also be careful about the flux-core solder you use, and what type of flux it contains. I've seen several MMC failures where the caps were directly mounted to phenolic or FR-4 PCBA material, and eventually failed due to surface tracking. The surface tracking appeared to be related to the flux residue that was left on the board. RMA (rosin, mildly activated) flux may require isopropyl alcohol or commercial flux removal solvent to remove it, followed by the hot-water wash process. Organic acid flux residue can be removed by thorough cleaning with water.
The biggest factor in surface tracking failure is probably component spacing, and awareness that the potential for surface tracking is affected by humidity, dust contamination, etc.
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Patrick wrote ...
but if i need 40 diodes in series then thats pretty long.
You can always wind them into a helix on a mandrel coil former, which you then immerse in a tube of dielectric oil, a solution which makes them shorter but fatter.
You see this solution used in C&W designs of the 1970s and 80s before monolithic HV Si diodes became generally available in current ratings beyond the milliamp or two needed for TV EHT service.
A refinement might be to use a mandrel with a cruciform cross-section - as one sees in some high power RF inductors - to minimise opportunities for surface tracking over the coil former.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Proud Mary wrote ...
Patrick wrote ...
but if i need 40 diodes in series then thats pretty long.
You can always wind them into a helix on a mandrel coil former, which you then immerse in a tube of dielectric oil, a solution which makes them shorter but fatter.
You see this solution used in C&W designs of the 1970s and 80s before monolithic HV Si diodes became generally available in current ratings beyond the milliamp or two needed for TV EHT service.
A refinement might be to use a mandrel with a cruciform cross-section - as one sees in some high power RF inductors - to minimise opportunities for surface tracking over the coil former.
I am considering this, to make a cross out of acrylic, but the spiral wont cause inducance problems? A 100kHz square wave is pretty fast and includes harmonics at the 5th order.
jpsmith123 wrote ...
If the diode strings are part of a voltage multiplier, then you might as well put the capacitors on the board too, right?
Its not for a CW Multiplier, i need a discrete diode to go with my many HV resistors. Like here:
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Patrick wrote ...
Proud Mary wrote ...
Patrick wrote ...
but if i need 40 diodes in series then thats pretty long.
You can always wind them into a helix on a mandrel coil former, which you then immerse in a tube of dielectric oil, a solution which makes them shorter but fatter.
You see this solution used in C&W designs of the 1970s and 80s before monolithic HV Si diodes became generally available in current ratings beyond the milliamp or two needed for TV EHT service.
A refinement might be to use a mandrel with a cruciform cross-section - as one sees in some high power RF inductors - to minimise opportunities for surface tracking over the coil former.
I am considering this, to make a cross out of acrylic, but the spiral wont cause inducance problems? A 100kHz square wave is pretty fast and includes harmonics at the 5th order.
You can calculate XL @ 100 kHz once you have made decisions over d and the length of each diode element i.e. including its wire and termination i.e. to arrive at the total number of turns N.
In the meantime, I will try and fish out some old papers where the helical diode units are described in more detail than I can now remember. ('Ere long we shall have regressed to the Voltaic Pile and the Electrophorus! )
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Proud Mary wrote ...
You can calculate XL @ 100 kHz once you have made decisions over d and the length of each diode element i.e. including its wire and termination i.e. to arrive at the total number of turns N.
In the meantime, I will try and fish out some old papers where the helical diode units are described in more detail than I can now remember. ('Ere long we shall have regressed to the Voltaic Pile and the Electrophorus! )
Im more worried about the " snapy-ness " of the switching action with so many diodes in series. Instead of just the simple impedance.
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.
Putting many diodes in series for a HV diode.
)