Developing HV DC Pulses...

[John Larkin]

On Thu, 11 May 2023 08:55:05 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:

In the famous words of Rodney King, \"Can\'t we just get along\"

Tell me how to control a tube. Can I drive it with a 555?

First thing is to pick a tube and get its data sheet.

> Do I need to run the 555 from plus 3V and minus 7V or some combination to get full off and full on?

Depends on the tube. I\'d suggest a mosfet-tube cascode so you\'d only
need 5 volts drive.

Rather that a pull down resistor scenario, can I just put the tube in series with the load and switch it? 18pf, 200M?+ load.
That would be better for upscaling, eliminating a 100watt 10M? resistor.

To drive a capacitive load, something has to pull up and something has
to pull down, charge and discharge.

A resistor is a cheap, safe pullup, but you shouldn\'t need a 100 watt
resistor.

7 KV across a 10 meg resistor is 5 watts. Pulsed at a low duty cycle
you\'d be below 1 watt. A string of 1/4 watt resistors would be fine.

Pick a tube (and a socket!) that you can get and we\'ll work out a
circuit. Group project. That would be fun, to design something with a
tube, like in olden times.

A tube thing would look cool, as a science project. The teachers and
kids have probably never seen one.

 

[John Larkin]

On Thu, 11 May 2023 09:19:46 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Thu, 11 May 2023 08:55:05 -0700 (PDT), Lamont Cranston
amdx62@gmail.com> wrote:

In the famous words of Rodney King, \"Can\'t we just get along\"

Tell me how to control a tube. Can I drive it with a 555?

First thing is to pick a tube and get its data sheet.

Do I need to run the 555 from plus 3V and minus 7V or some combination to get full off and full on?

Depends on the tube. I\'d suggest a mosfet-tube cascode so you\'d only
need 5 volts drive.

Rather that a pull down resistor scenario, can I just put the tube in series with the load and switch it? 18pf, 200M?+ load.
That would be better for upscaling, eliminating a 100watt 10M? resistor.

To drive a capacitive load, something has to pull up and something has
to pull down, charge and discharge.

A resistor is a cheap, safe pullup, but you shouldn\'t need a 100 watt
resistor.

7 KV across a 10 meg resistor is 5 watts. Pulsed at a low duty cycle
you\'d be below 1 watt. A string of 1/4 watt resistors would be fine.

Pick a tube (and a socket!) that you can get and we\'ll work out a
circuit. Group project. That would be fun, to design something with a
tube, like in olden times.

A tube thing would look cool, as a science project. The teachers and
kids have probably never seen one.

ebay has 6BK4\'s.

 

[Lamont Cranston]

On Thursday, May 11, 2023 at 11:20:01 AM UTC-5, John Larkin wrote:

On Thu, 11 May 2023 08:55:05 -0700 (PDT), Lamont Cranston
amd...@gmail.com> wrote:

In the famous words of Rodney King, \"Can\'t we just get along\"

Tell me how to control a tube. Can I drive it with a 555?
First thing is to pick a tube and get its data sheet.
Do I need to run the 555 from plus 3V and minus 7V or some combination to get full off and full on?
Depends on the tube. I\'d suggest a mosfet-tube cascode so you\'d only
need 5 volts drive.

Do I still need a negative supply to pull the grid negative?

Rather that a pull down resistor scenario, can I just put the tube in series with the load and switch it? 18pf, 200M?+ load.
That would be better for upscaling, eliminating a 100watt 10M? resistor.

To drive a capacitive load, something has to pull up and something has
to pull down, charge and discharge.

OK, rejecting the tube in series with the load idea.

A resistor is a cheap, safe pullup, but you shouldn\'t need a 100 watt
resistor.

Ya, musta been a glitch in my microsoft calculator. ;-)

7 KV across a 10 meg resistor is 5 watts. Pulsed at a low duty cycle
you\'d be below 1 watt. A string of 1/4 watt resistors would be fine.


Pick a tube (and a socket!) that you can get and we\'ll work out a
circuit. Group project. That would be fun, to design something with a
tube, like in olden times.

Part of the reason I\'m leaning towards a tube is I don\'t want to be troubleshooting why I\'m popping transistors or mosfets,
I think the tube is just more robust in the face of problems, but I could be wrong.
No one has addressed the 1300H secondary that I will be unloading. Since this will now be a filtered bridge output maybe
the filter caps would limit any spike, but that has spooked me on Solid state.
I\'m willing to go SS if my spike issue is addressed. On the other hand I\'m think of an over build for later schemes, so maybe tube,
or 30kV of mosfets. Actually a filtered 30kV neon transformer is more like 42kV, but we could limit it.

I\'m gathering supplies to setup 3 vessels running at increasing voltages to see if production is linear with voltage input and to see if there is an increase of voltage that has diminishing returns. Will build a resistive voltage divider to pick voltages from. Someone mentioned a ground plain under the resistors, that seems counter intuitive. Should I mount the HV standoffs on Lexan or a copper PCB, and then do I earth ground the pcb?

A tube thing would look cool, as a science project. The teachers and
kids have probably never seen one.

 

[Lamont Cranston]

On Thursday, May 11, 2023 at 12:10:55 PM UTC-5, John Larkin wrote:

> ebay has 6BK4\'s.

27,000Vdc, Max Plate current 1.6ma, OK, not a lot of overkill, but cheap.

https://tubedata.tubes.se/sheets/127/6/6BK4.pdf

I\'ll wait a bit and see if there is further discussion, and might order later today, along with an octal socket.
I\'ll probably double up, is it possible to series two tubes if we later want higher Voltage of parallel for more current.

 

[John Larkin]

On Thu, 11 May 2023 10:44:14 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:

On Thursday, May 11, 2023 at 12:10:55?PM UTC-5, John Larkin wrote:

ebay has 6BK4\'s.

27,000Vdc, Max Plate current 1.6ma, OK, not a lot of overkill, but cheap.

https://tubedata.tubes.se/sheets/127/6/6BK4.pdf

I\'ll wait a bit and see if there is further discussion, and might order later today, along with an octal socket.
I\'ll probably double up, is it possible to series two tubes if we later want higher Voltage of parallel for more current.

Driving the grid positive would turn it on harder. Tubes are
depletion/enhancement devices. The rated max plate current need not be
respected here.

Series would be very tricky. Do you want more than 27 KV?

One trick in driving Pockels Cells is to drive the two electrodes
antiphase. That could be done with two grounded tubes. Not a bad idea
even at lower voltages. Maybe.

 

[Lamont Cranston]

On Thursday, May 11, 2023 at 1:08:38 PM UTC-5, John Larkin wrote:

Driving the grid positive would turn it on harder. Tubes are
depletion/enhancement devices. The rated max plate current need not be
respected here.

Series would be very tricky. Do you want more than 27 KV?

Not now, we are working max 9kV times 1.414 or 12.7kV with the current neon sign transformer.
but there are 30kV neon sign transformers for later.
Just thinking about when we upscale and have more space between electrodes,
we would need higher voltage to get the same V/cm electric field.

I\'m starting to think any spike from unloading the 1300H secondary is, \"in my mind only\", as no one has address it.

Mikek

One trick in driving Pockels Cells is to drive the two electrodes
antiphase. That could be done with two grounded tubes. Not a bad idea
even at lower voltages. Maybe.

 

[John Larkin]

On Thu, 11 May 2023 10:24:48 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:

On Thursday, May 11, 2023 at 11:20:01?AM UTC-5, John Larkin wrote:
On Thu, 11 May 2023 08:55:05 -0700 (PDT), Lamont Cranston
amd...@gmail.com> wrote:

In the famous words of Rodney King, \"Can\'t we just get along\"

Tell me how to control a tube. Can I drive it with a 555?
First thing is to pick a tube and get its data sheet.
Do I need to run the 555 from plus 3V and minus 7V or some combination to get full off and full on?
Depends on the tube. I\'d suggest a mosfet-tube cascode so you\'d only
need 5 volts drive.

Do I still need a negative supply to pull the grid negative?

Rather that a pull down resistor scenario, can I just put the tube in series with the load and switch it? 18pf, 200M?+ load.
That would be better for upscaling, eliminating a 100watt 10M? resistor.

To drive a capacitive load, something has to pull up and something has
to pull down, charge and discharge.

OK, rejecting the tube in series with the load idea.

A resistor is a cheap, safe pullup, but you shouldn\'t need a 100 watt
resistor.

Ya, musta been a glitch in my microsoft calculator. ;-)

7 KV across a 10 meg resistor is 5 watts. Pulsed at a low duty cycle
you\'d be below 1 watt. A string of 1/4 watt resistors would be fine.


Pick a tube (and a socket!) that you can get and we\'ll work out a
circuit. Group project. That would be fun, to design something with a
tube, like in olden times.

Part of the reason I\'m leaning towards a tube is I don\'t want to be troubleshooting why I\'m popping transistors or mosfets,
I think the tube is just more robust in the face of problems, but I could be wrong.

My first job interview, I told the guy that I preferred tubes to
transistors because transistors were expensive and tubes were hard to
blow up. He said \"that won\'t do\" and dismissed me. I said the same
thing at the next interview and that guy laughed and hired me. I
designed $200 million worth of stuff for him.

Actually, I just remembered, I did design two tube-type HV pulse
generators for microwave spectroscopy, high school summer job. Both
were 2-tube half-bridge topology, one box with hard tubes and one with
thyratrons. Envision HV-insulated filament transformers and pulse
transformer grid drives. Envision thyratron shoot-through.

> No one has addressed the 1300H secondary that I will be unloading.

1300H?

 

[Lamont Cranston]

On Thursday, May 11, 2023 at 1:21:28 PM UTC-5, John Larkin wrote:

> 1300H?

Using a DE-5000 at 100Hz, primary is 340mH and secondary is 1271 Henry.
Approximately 295kΩ output impedance.

Mikek

 

[John Larkin]

On Thu, 11 May 2023 11:33:05 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:

On Thursday, May 11, 2023 at 1:21:28?PM UTC-5, John Larkin wrote:

1300H?

Using a DE-5000 at 100Hz, primary is 340mH and secondary is 1271 Henry.
Approximately 295k? output impedance.

Mikek

DE-5000?

 

[Lamont Cranston]

On Thursday, May 11, 2023 at 2:32:17 PM UTC-5, John Larkin wrote:

On Thu, 11 May 2023 11:33:05 -0700 (PDT), Lamont Cranston


1300H?

Using a DE-5000 at 100Hz, primary is 340mH and secondary is 1271 Henry.
Approximately 295k? output impedance.

Mikek

DE-5000?

DE-5000.

https://www.ietlabs.com/pdf/Manuals/DE_5000_im.pdf

 

[Lamont Cranston]

On Thursday, May 11, 2023 at 1:08:38 PM UTC-5, John Larkin wrote:

> Driving the grid positive would turn it on harder.

Got it, but, the tube curves show up to 7 V negative to pinch it off.
Do I need a ± supply to switch it on and off hard.
Mikek

 

[Joe Gwinn]

On Thu, 11 May 2023 12:35:28 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:

On Thursday, May 11, 2023 at 2:32:17?PM UTC-5, John Larkin wrote:
On Thu, 11 May 2023 11:33:05 -0700 (PDT), Lamont Cranston


1300H?

Using a DE-5000 at 100Hz, primary is 340mH and secondary is 1271 Henry.
Approximately 295k? output impedance.

Mikek

DE-5000?

DE-5000.

https://www.ietlabs.com/pdf/Manuals/DE_5000_im.pdf

It\'s the original General Radio desktop Impedance Meter design, now
cloned. IET bought the wreckage of Genrad, and moved manufacturing to
China. I\'m guessing that the DE-5000 is made by that original Chinese
manufacturer, now freed somehow.

The patents are informative:

US4181949, US4196475, and US4342089 to Henry P.Hall of Genrad Inc, all
in the 1980s.

Joe Gwinn

 

[John Larkin]

On Thu, 11 May 2023 12:59:07 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:

On Thursday, May 11, 2023 at 1:08:38?PM UTC-5, John Larkin wrote:

Driving the grid positive would turn it on harder.

Got it, but, the tube curves show up to 7 V negative to pinch it off.
Do I need a ± supply to switch it on and off hard.
Mikek

No, there is a simple, elegant circuit that needs just one small power
supply, plus the HV of course.

Sloman says that I am a hack who can only make minor tweaks to my own
circuits (which is an interesting bit of logic itself) so I think he
should contribute the first schematic.

Of course, he won\'t use any of my dumb suggestions.

(I haven\'t used tubes since I was a kid. A 6BK4 actually makes sense
here. No mosfet is going to have 27 KV Vd-s or 1 pF drain
capacitance.)

 

[John Larkin]

On Thu, 11 May 2023 12:35:28 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:

On Thursday, May 11, 2023 at 2:32:17?PM UTC-5, John Larkin wrote:
On Thu, 11 May 2023 11:33:05 -0700 (PDT), Lamont Cranston


1300H?

Using a DE-5000 at 100Hz, primary is 340mH and secondary is 1271 Henry.
Approximately 295k? output impedance.

Mikek

DE-5000?

DE-5000.

https://www.ietlabs.com/pdf/Manuals/DE_5000_im.pdf

Even if the neon transformer secondary is 1200 H, which I guess it
could be, that\'s only 500K ohms at 60 Hz. Shouldn\'t matter.

Neon sign transformers are soft, by design.

What actually matters here is leakage inductance, probably a lot lower
than 1200 H. Measure the secondary L with the primary shorted.

Those little RLC meters can be wildly off, too, measuring L.

 

[Lamont Cranston]

On Thursday, May 11, 2023 at 4:05:47 PM UTC-5, John Larkin wrote:

(I haven\'t used tubes since I was a kid. A 6BK4 actually makes sense
here. No mosfet is going to have 27 KV Vd-s or 1 pF drain
capacitance.)

I have made my own stab at a design, not understanding bias polarity and looking at a website for some info.
I\'m putting it out for corrections to learn something.
https://www.dropbox.com/s/knhc6s5jfcbrvrj/OiL%20water%20Tube%20Circuit..jpg?dl=0

Mikek

 

[Lamont Cranston]

On Thursday, May 11, 2023 at 4:14:15 PM UTC-5, John Larkin wrote:

What actually matters here is leakage inductance, probably a lot lower
than 1200 H. Measure the secondary L with the primary shorted.

The secondary measures 604 H with primary shorted.
What does that mean?

Mikek

 

[John Larkin]

On Thu, 11 May 2023 14:18:20 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:

On Thursday, May 11, 2023 at 4:05:47?PM UTC-5, John Larkin wrote:


(I haven\'t used tubes since I was a kid. A 6BK4 actually makes sense
here. No mosfet is going to have 27 KV Vd-s or 1 pF drain
capacitance.)

I have made my own stab at a design, not understanding bias polarity and looking at a website for some info.
I\'m putting it out for corrections to learn something.
https://www.dropbox.com/s/knhc6s5jfcbrvrj/OiL%20water%20Tube%20Circuit..jpg?dl=0

Mikek

Let\'s give Bill 24 hours, plenty of time for something simple like
this, and if he doesn\'t invent something good, I\'ll try a sketch.

Meanwhile, buy some resistors and a few 2N7000\'s.

 

[John Larkin]

On Thu, 11 May 2023 14:22:09 -0700 (PDT), Lamont Cranston
<amdx62@gmail.com> wrote:

On Thursday, May 11, 2023 at 4:14:15?PM UTC-5, John Larkin wrote:

What actually matters here is leakage inductance, probably a lot lower
than 1200 H. Measure the secondary L with the primary shorted.

The secondary measures 604 H with primary shorted.
What does that mean?

Mikek

That means that the primary and secondary coils are loosely coupled
magnetically. Neon transformers operate into almost a short circuit,
so they are designed to have high output impedances.

The 604H value is relevant here, since the primary will be driven from
a low impedance AC supply. 600H is only 220K ohms at 60 Hz. Should be
fine in your application. The rectified and filtered HV DC might droop
a little when you pulse hard.

 

[whit3rd]

On Thursday, May 11, 2023 at 12:59:11 PM UTC-7, Lamont Cranston wrote:

On Thursday, May 11, 2023 at 1:08:38 PM UTC-5, John Larkin wrote:

Driving the grid positive would turn it on harder.
Got it, but, the tube curves show up to 7 V negative to pinch it off.
Do I need a ± supply to switch it on and off hard.

Don\'t see why; your current is a milliamp (or less), so simply driving grid and cathode in opposite
senses will give you +12 to -12 off of a single +12 power source.

 

[Lamont Cranston]

On Thursday, May 11, 2023 at 6:00:46 PM UTC-5, whit3rd wrote:

On Thursday, May 11, 2023 at 12:59:11 PM UTC-7, Lamont Cranston wrote:
On Thursday, May 11, 2023 at 1:08:38 PM UTC-5, John Larkin wrote:

Driving the grid positive would turn it on harder.
Got it, but, the tube curves show up to 7 V negative to pinch it off.
Do I need a ± supply to switch it on and off hard.
Don\'t see why; your current is a milliamp (or less), so simply driving grid and cathode in opposite
senses will give you +12 to -12 off of a single +12 power source.

I\'m getting info that you don\'t want the grid to go positive, just to 0V and negative a few volts, in relation to the cathode.
As I understand it, with the grid at 0V the tube has no current flow, as the grid voltage goes more negative
current starts to flow until it is turned all the on. Is that correct?
Also, what is the voltage drop across a tube in full conduction?
Does it get pretty close to 0V, or 10V or 100V?
Mikek