Zener noise / oscillations

Maybe try a few avalanche rated mosefts? You'd have to test them...

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Thanks,
Fred.

radiation.

But what? My tube handbooks are in storage and I haven't used a shunt regulator in close to 40 years. Some had a thick, rubberized lead covering to stop the X-Ray radiation. I remember that GE made them, and they were a replacement for the 6BK4. There were so few failures that I can't remember the type number. More were replaced as PM when installing a new FB transformer than from excessive HV problems. I spent more time on industrial electronics than tube type color TVs. I did repair the solid state sets because the older techs didn't understand transistors.

On a sunny day (Sat, 28 Jul 2012 09:09:43 -0400) it happened "Michael A. Terrell" wrote in :

radiation.

But lead tubes?

I had a tube handbook, it was written by an old schoolmate, dunno what happened to it (or him after he was fired).

Some teachers did not either, I remember one guy asking in classes: "Sir what exactly is a complementary pair?" And he almost got thrown out, as teacher thought it was a sex joke. It took some to convince the teacher those things really existed.

Colored TV started here in 1967, by that time most antique stuff was gone, the first Philips sets here had a PD500 stabilizer.

The glass in those got a nice blue color due to roentgen radiation after some use. There is a guy wit ha website who made roentgen pictures of screws in wood with some HV and an old tube: They were in a closed metal case of course. I had many at one time, should have kept some of that colored glass, but every time I type 'colored' I think of Obanana, so I was right dumping them.

How? It's effectively a switch. Flyback pulse amplitude, hence HV, is largely determined by the inductance and parallel capacitance of the deflection coils. During flyback, the system is resonant for a half-cycle at 1/(2*t(flyback)). The tube will be off.

Capacitance from the HO tube plate to ground *will* affect the HV. Some unscrupulous "repairers" used to hang C off the plate to get the HV down, and increase width, rather than fix the underlying problem.

A controlled reactance from plate to ground would control HV.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

Europeon lookalike - PD500.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

Yes, but there must *be* some. I shall have to look out the manual, if I have it.

I use a 576. Even at minimum load setting, there is some residual resistance (the current sensing resistor).

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

One could probably make a sinewave oscillator by coupling an LC tank to a zener.

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
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Transistors make poor ideal switches, and tubes even less so. Examples: weaker grid drive will increase "saturation" voltage and shorten the conduction angle, resulting in less energy, less width and less HV. Screen supply has a similar effect, and series resistance to the screen controls saturation voltage and peak plate current.

Typical pulse regulators used another sweep tube, or a different beam triode, to carry a little current out of the peak. Basically the same thing, as the beam triodes used in this application were ordinary sweep tubes with a finer control grid and no screen grid. The other electrodes (cathode, beam forming plates, anode) are identical to the respective sweeps, and the mica supports have unused holes for a screen grid. Result: high gain (gm 30~60mmho, mu > 100) and very low perveance (maybe 100mA at zero bias, 1kV plate).

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Unfortunately, the idea is to maintain HV, hence deflection sensitivity, hence size, with fluctuations in beam current. That scheme modulates scan current, as well as HV. Perhaps usable for setting, but no good for dynamic modulation, apart from, maybe East-West pincushion correction.

That's a much more viable scheme.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

The newer flybacks could supply enough current that the change in beam current didn't affect the HV regulation. If you did see a change the HV rectifire was failing. That was rare, with triplers. They either worked or didn't. The usual failure mode was a cracked case, and arcing.

The H drive was more than just a pulse. It had to be properly shaped to maintain good H linearity. That wasn't done in early TVs, Monochrome or Color.

radiation.

yes, the jacket was about 1/4" thick green or grayish and made with lead dust & a synthetic rubber. You could sometimes peel it off of an old tube, while the glass would break on others if you tried.

Instead of a 25 kV breakdown device, how about a 25kV resistor and a series of current limit diodes...if you feed 27 kV in, at 100V per diode, it only takes twenty-one CL diodes and a single resistor.

If the CL diodes are set at 500 uA, the resistor will dissipate

12.5 watts, and the CL diodes another watt or so.

Well, ASS-u-ME-ing an additional supply, one could use a 431, a FET and a few resistors (variant on our original Codatron(TM) design) to produce a decent 500V reference, and then stack a bunch of FETs and resistors to multiply by 50..too expensive.

radiation.

The original Corotron(TM) 25KV regulator IS made with a metal shell.

Put 9 in series; noise seen from 20uA to 100uA then gets quiet above that; noise increases with current.

The TV shunt regulator is to keep the voltage constant, and so must pas varying current..

On a sunny day (Sun, 29 Jul 2012 00:29:49 -0700) it happened Robert Baer wrote in :

radiation.

I did some google searching. seems hard to find the TV version, is this it?

So a $2 transistor and two resistors for each subsequent 1500V is too much? And a stack of 431s (if they worked) isn't???

Then your product is impossible.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

They're not zeners, but *avalanche* diodes. Different effect. Remember your posted curves of emitter and collector breakdown?

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)