Hi,

Because all else failed, I want to go to the extreme in blowing out the
cathode-G1 short, from which my Eizo T766 19" CRT suffers. After the capacitor
discharge, the short has gone from 1K ohm, to 0.0 Ohm, and I can make the
internal wiring of the tube red hot by running 3A of current through it...

The repair FAQ mentions using a Tesla coil. The nearest thing to a Tesla coil I
used, was the 750V G2 of another (scrap) monitor, but that can only be
sustained for a fraction of a second before the monitor shuts off; nowhere
near the 10 seconds the repair FAQ states.

My question is this: can I use the anode and ground wire of another monitor to
act as my Tesla coil? How do I prevent breakdown of air and/or vacuum around
the CRT pins and such (I don't want arcing in the wrong place). And, very
importantly, can the flyback sustain such an arc? I've seen videos on the
internet in which they use the anode of a monitor to create a sustainable arc
between anode and probably ground, but I don't know if it needs to be modified
for that (because an arc is basically a short).

I am aware of the dangers BTW; when I do this, I will take proper safety
measures.

Regards,

Wiebe Cazemier

On Wed, 21 May 2008 15:00:57 +0200, Wiebe Cazemier wrote:
Because all else failed, I want to go to the extreme in blowing out the
cathode-G1 short, from which my Eizo T766 19" CRT suffers. After the capacitor
discharge, the short has gone from 1K ohm, to 0.0 Ohm, and I can make the
internal wiring of the tube red hot by running 3A of current through it...
...
My question is this: can I use the anode and ground wire of another monitor to
act as my Tesla coil? How do I prevent breakdown of air and/or vacuum
around...

I may be going in over my head here but...

You've run 3A of current through this short, and it's still there?

I wouldn't think the flyback circuit would be able to deliver even 3mA,
let alone 3A, and certainly not for 10 seconds.

I'd definitely want other opinions first but my thought is that you're
going to have to throw current at this problem - if 3A isn't enough, use
more - and just hope the short burns out before anything that's actually
necessary for the CRT to work. I would suggest precautions against damage
to the envelope of the tube, possibly up to implosion. (probably not
likely but with dangerous consequences if it does happen)

On Wednesday 21 May 2008 16:16, Doug Smith W9WI wrote:

I may be going in over my head here but...

You've run 3A of current through this short, and it's still there?

I wouldn't think the flyback circuit would be able to deliver even 3mA,
let alone 3A, and certainly not for 10 seconds.

Still, 25000V of the flyback can ionize air and form an arc, 3A at 4V can't do
that... I hope 25000V can ionize the short as well.


I'd definitely want other opinions first but my thought is that you're
going to have to throw current at this problem - if 3A isn't enough, use
more - and just hope the short burns out before anything that's actually
necessary for the CRT to work. I would suggest precautions against damage
to the envelope of the tube, possibly up to implosion. (probably not
likely but with dangerous consequences if it does happen)

I think high voltage low current is less destructive to the elements inside the
tube than low voltage high current. I could run more amps through the short,
but I kind of have the feeling it won't last... The cathodes may be
impregnated, and therefore able to handle more current, but still... Perhaps
I've already damaged them.

BTW, I was thinking. When using the Tesla coil method, can one even think in
terms of connecting wires to the CRT pins? The 25000V will arc between the
connectors anyway. The FAQ speaks of "running the coil around the pins". Does
that simply mean: connecting Tesla coil ground to G1 and move the anode near
the pins, so an arc will form between any pin that has a connection with G1?

On Wednesday 21 May 2008 18:55, Wiebe Cazemier wrote:

BTW, I was thinking. When using the Tesla coil method, can one even think in
terms of connecting wires to the CRT pins? The 25000V will arc between the
connectors anyway. The FAQ speaks of "running the coil around the pins". Does
that simply mean: connecting Tesla coil ground to G1 and move the anode near
the pins, so an arc will form between any pin that has a connection with G1?

You know, like this:

http://video.google.com/videoplay?do...67613158202368

Wiebe Cazemier wrote in
b.home.nl:

Hi,

Because all else failed, I want to go to the extreme in blowing out the
cathode-G1 short, from which my Eizo T766 19" CRT suffers. After the
capacitor discharge, the short has gone from 1K ohm, to 0.0 Ohm, and I
can make the internal wiring of the tube red hot by running 3A of
current through it...

The repair FAQ mentions using a Tesla coil. The nearest thing to a Tesla
coil I used, was the 750V G2 of another (scrap) monitor, but that can
only be sustained for a fraction of a second before the monitor shuts
off; nowhere near the 10 seconds the repair FAQ states.

My question is this: can I use the anode and ground wire of another
monitor to act as my Tesla coil? How do I prevent breakdown of air
and/or vacuum around the CRT pins and such (I don't want arcing in the
wrong place). And, very importantly, can the flyback sustain such an
arc? I've seen videos on the internet in which they use the anode of a
monitor to create a sustainable arc between anode and probably ground,
but I don't know if it needs to be modified for that (because an arc is
basically a short).

I think you will need a LARGEr value capacitor, charged up with plenty of
coulombs of electrons.

Keep your wires thick and short.

With the dead short, you don't need high voltage, you need high current but
only for a short time.
You want to try to blow out the weakest point in the circuit and to hope it
is the recently created short.

It is too late for the Tesla coil. That might have been useful when there
was not a dead short.

















--
bz 73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

On Wednesday 21 May 2008 19:07, Meat Plow wrote:

What about using a stun-gun or taser?

I guess the effect is the same, but I have a spare monitor with flyback, I
don't have stunguns lying around...

Wiebe Cazemier wrote:
Hi,

Because all else failed, I want to go to the extreme in blowing out the
cathode-G1 short, from which my Eizo T766 19" CRT suffers. After the capacitor
discharge, the short has gone from 1K ohm, to 0.0 Ohm, and I can make the
internal wiring of the tube red hot by running 3A of current through it...

The repair FAQ mentions using a Tesla coil. The nearest thing to a Tesla coil I
used, was the 750V G2 of another (scrap) monitor, but that can only be
sustained for a fraction of a second before the monitor shuts off; nowhere
near the 10 seconds the repair FAQ states.

My question is this: can I use the anode and ground wire of another monitor to
act as my Tesla coil? How do I prevent breakdown of air and/or vacuum around
the CRT pins and such (I don't want arcing in the wrong place). And, very
importantly, can the flyback sustain such an arc? I've seen videos on the
internet in which they use the anode of a monitor to create a sustainable arc
between anode and probably ground, but I don't know if it needs to be modified
for that (because an arc is basically a short).

I am aware of the dangers BTW; when I do this, I will take proper safety
measures.

Regards,

Wiebe Cazemier


That tube is a goner. If you managed to heat the internal wires up red
hot, you've welded whatever bits were shorting together. You could try
charging up a large electrolytic to a couple hundred volts via rectified
mains and dumping that into there, but something other than the short
will probably act as a fuse.

On Wednesday 21 May 2008 19:03, bz wrote:

I think you will need a LARGEr value capacitor, charged up with plenty of
coulombs of electrons.

Keep your wires thick and short.

With the dead short, you don't need high voltage, you need high current but
only for a short time.
You want to try to blow out the weakest point in the circuit and to hope it
is the recently created short.

It is too late for the Tesla coil. That might have been useful when there
was not a dead short.

I just tried that, of my own accord, and I think the weakest point in the
circuit was the internal connection to the cathodes... The shorts are gone,
but it doesn't display an image anymore. That is, it displays a blueish grey
image, with visible retrace lines (somewhat blurry). And when I turn it off,
there still is this characteristic contraction of the image, which ends in a
blue, red and green spot in the middle.

"James Sweet" wrote in message
news:8IYYj.2281$aJ1.47@trndny03...

Wiebe Cazemier wrote:
Hi,

Because all else failed, I want to go to the extreme in blowing out the
cathode-G1 short, from which my Eizo T766 19" CRT suffers. After the
capacitor
discharge, the short has gone from 1K ohm, to 0.0 Ohm, and I can make the
internal wiring of the tube red hot by running 3A of current through
it...

The repair FAQ mentions using a Tesla coil. The nearest thing to a Tesla
coil I
used, was the 750V G2 of another (scrap) monitor, but that can only be
sustained for a fraction of a second before the monitor shuts off;
nowhere
near the 10 seconds the repair FAQ states.

My question is this: can I use the anode and ground wire of another
monitor to
act as my Tesla coil? How do I prevent breakdown of air and/or vacuum
around
the CRT pins and such (I don't want arcing in the wrong place). And, very
importantly, can the flyback sustain such an arc? I've seen videos on the
internet in which they use the anode of a monitor to create a sustainable
arc
between anode and probably ground, but I don't know if it needs to be
modified
for that (because an arc is basically a short).

I am aware of the dangers BTW; when I do this, I will take proper safety
measures.

Regards,

Wiebe Cazemier


That tube is a goner. If you managed to heat the internal wires up red
hot, you've welded whatever bits were shorting together. You could try
charging up a large electrolytic to a couple hundred volts via rectified
mains and dumping that into there, but something other than the short will
probably act as a fuse.

Agreed! Time to either search for a new CRT for the item or off the original
to Video Display Corp to have it re-gunned. Either way it probably will not
be cost effective to do so.
IMHO: Continued application of processes you have already tried will not
only totally render the CRT inoperable but will probably also damage the
video drive and bias circuits connected to the CRT as a result.

On Thursday 22 May 2008 12:02, Art wrote:
Agreed! Time to either search for a new CRT for the item or off the original
to Video Display Corp to have it re-gunned. Either way it probably will not
be cost effective to do so.

Regunned? Is that possible?

I already called the repair service. It's going to cost me ? 500 to replace the
CRT... The irony is, if I can be sure I don't get it back with all kinds of
convergence errors and such (which a lot of T766's suffered from), I would be
willing to spend it, to avoid getting TFT for a while longer.

On Thursday 22 May 2008 12:02, Someone wrote:
IMHO: Continued application of processes you have already tried will not
only totally render the CRT inoperable but will probably also damage the
video drive and bias circuits connected to the CRT as a result.

Don't worry, everything I did was with a disconnected CRT socket. Furthermore,
testing with the CRT on was with the driver disconnected, so it didn't short
out.

Wiebe Cazemier wrote in news:d595a$48355326$d4cc82be
:


Regunned? Is that possible?

Google for
CRT repairs





--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

On Thu, 22 May 2008 13:04:06 +0200 Wiebe Cazemier
wrote in Message id:
me.nl:

On Thursday 22 May 2008 12:02, Art wrote:
Agreed! Time to either search for a new CRT for the item or off the original
to Video Display Corp to have it re-gunned. Either way it probably will not
be cost effective to do so.

Regunned? Is that possible?

I already called the repair service. It's going to cost me ? 500 to replace the
CRT... The irony is, if I can be sure I don't get it back with all kinds of
convergence errors and such (which a lot of T766's suffered from), I would be
willing to spend it, to avoid getting TFT for a while longer.

You'd pay $500 for a CRT monitor?

(And to think I gave away two 19" and one 21" a few months ago!)

On Wed, 21 May 2008 18:55:58 +0200, Wiebe Cazemier wrote:
I think high voltage low current is less destructive to the elements inside the
tube than low voltage high current. I could run more amps through the short,
but I kind of have the feeling it won't last... The cathodes may be
impregnated, and therefore able to handle more current, but still... Perhaps
I've already damaged them.

You have no control over the voltage/current ratio. E/I=R, where R is the
resistance of the short. (I'm sure much less than one ohm.)

If, somehow, you were able to find a supply big enough to actually deliver
25,000 volts across this short, it *would* draw 25,000 amps. Or much more.

(and I'd be quite confident it would clear the short. Probably very
spectacularly.)

A flyback power supply won't do this. Its internal resistance is way too
high. If it worked at all when connected to this short, its output would
be limited to WAY less than 25,000 volts. Probably to way less than *one*
volt.

On Thursday 22 May 2008 15:22, JW wrote:
You'd pay $500 for a CRT monitor?

(And to think I gave away two 19" and one 21" a few months ago!)

There are lot of 19" monitors available for almost nothing. Mostly shadowmask
types, which I dislike. A popular site among "geeks" in the Netherlands here,
is tweakers.net. Their second hand offering doesn't include a single T766 or
109P model, both of which use trinitron(-like) tubes. Other second-hand sites
do include 109P's and older Eizo models, but not newer Eizo models like the
T766's, or T966 (21" model). And the 109P didn't meet with my demands, because
of severe convergence problems (I tried about 8 of them...)

The point is, you can get a lot of average CRT's for almost nothing, but the
quality that my T766 offered is hard to get. One reason is that Eizo has very
strict rules when it comes to the quality of the CRTs they use; they select
the best ones from manufacturing batches.

And to top it off, 500 EU is 783.85 USD... Think of it this way. I will
absolutely refuse any TN TFT panel (the "standard" kind), and preferably I
want an IPS panel if I am forced to buy a TFT. But then I need to come up with
at least ? 1000, and still have a black level I can never be satisfied with.
And IPS has slower response than TN.

If you need a few amps of current to blow out a direct short, get a good
5 Amp or heavier 12 volt supply. Get enough capacitors that you can put
in parallel to build up at least 60,000 uF or more. Put a 3 or 4 ohm 10
Watt resistor in series with the caps to the power supply. This way,
when switching on to charge the caps, you don't blow the "@ss" off the
power supply.

After about 20 to 30 seconds or so, connect your clip leads directly
from the caps to whatever you want to blow the short out of.

If the above does not work, and you want to feel like a really weird mad
scientist (I am serious), get a few fully charged 120 Amp automobile
batteries. Connect them in parallel. The peak full load output should be
more than 1200 Amps. If this does not blow out the short, then you know
that probably nothing will.

With a few automobile batteries in parallel the peak output can exceed
14 kW. Just take care that you don't injure yourself or start an
electrical fire with this!

--

JANA
_____


"Wiebe Cazemier" wrote in message
b.home.nl...
Hi,

Because all else failed, I want to go to the extreme in blowing out the
cathode-G1 short, from which my Eizo T766 19" CRT suffers. After the
capacitor
discharge, the short has gone from 1K ohm, to 0.0 Ohm, and I can make
the
internal wiring of the tube red hot by running 3A of current through
it...

The repair FAQ mentions using a Tesla coil. The nearest thing to a Tesla
coil I
used, was the 750V G2 of another (scrap) monitor, but that can only be
sustained for a fraction of a second before the monitor shuts off;
nowhere
near the 10 seconds the repair FAQ states.

My question is this: can I use the anode and ground wire of another
monitor to
act as my Tesla coil? How do I prevent breakdown of air and/or vacuum
around
the CRT pins and such (I don't want arcing in the wrong place). And,
very
importantly, can the flyback sustain such an arc? I've seen videos on
the
internet in which they use the anode of a monitor to create a
sustainable arc
between anode and probably ground, but I don't know if it needs to be
modified
for that (because an arc is basically a short).

I am aware of the dangers BTW; when I do this, I will take proper safety
measures.

Regards,

Wiebe Cazemier

On Sunday 25 May 2008 05:33, JANA wrote:

If you need a few amps of current to blow out a direct short, get a good
5 Amp or heavier 12 volt supply. Get enough capacitors that you can put
in parallel to build up at least 60,000 uF or more. Put a 3 or 4 ohm 10
Watt resistor in series with the caps to the power supply. This way,
when switching on to charge the caps, you don't blow the "@ss" off the
power supply.

After about 20 to 30 seconds or so, connect your clip leads directly
from the caps to whatever you want to blow the short out of.

If the above does not work, and you want to feel like a really weird mad
scientist (I am serious), get a few fully charged 120 Amp automobile
batteries. Connect them in parallel. The peak full load output should be
more than 1200 Amps. If this does not blow out the short, then you know
that probably nothing will.

With a few automobile batteries in parallel the peak output can exceed
14 kW. Just take care that you don't injure yourself or start an
electrical fire with this!


I had already tried this, but in an elegant way. I charged up a 4700 uF cap
with my current limited supply to 30V and used that to blow out the short. The
short is gone, but so is the connection to the cathodes. Bye bye tube...

Wiebe Cazemier wrote:
Hi,

Because all else failed, I want to go to the extreme in blowing out the
cathode-G1 short, from which my Eizo T766 19" CRT suffers. After the capacitor
discharge, the short has gone from 1K ohm, to 0.0 Ohm, and I can make the
internal wiring of the tube red hot by running 3A of current through it...


That's because you've now effectively welded the elements of the gun
assy together.


The repair FAQ mentions using a Tesla coil. The nearest thing to a Tesla coil I
used, was the 750V G2 of another (scrap) monitor, but that can only be
sustained for a fraction of a second before the monitor shuts off; nowhere
near the 10 seconds the repair FAQ states.


It's not going to help. There's no way a home Tesla coil is going to
develop anywhere near 3A (you wouldn't want to be near it anyway).
With the short now reading zero ohms, the only way to eliminate the
short is more current. The problem is is that once you run enough
current into the tube to eliminate the short, one of the elements (or
the internal connecting wires) will fail before the short will, and
the tube will be left with zero output.

Sorry.