Stacking 431s does work, but that cannot be used for this app as the standby or keep-alive current is too high. And the other reference voltage parts cost too much (say 2.5V times
10,000 times price each).
running at:
specs...
adjusted byte
Most especially do NOT disturb someone doing the "impossible"!
Not red, is yellow; digital camera and color inversion does the rest (note BLUE graticule).
Worst one seen: Vishay MMBZ5266C-V-GS08, 68V SOT-23; expect their DO-35 to be exactly the same (one datasheet covers all of them). 20V/div and 50uA/div using the 7CT1N curve tracer; no series resistance selectable.
On a sunny day (Thu, 26 Jul 2012 17:45:17 -0500) it happened "Tim Williams" wrote in :
I worked for Tek, did some calibration and also QC. In calibration you get a book with steps to check and adjust, work through it, are not allowed to make any notes, and make everything in spec. In the next step, the QC, an OTHER person does the same, but adjusts nothing, just give it back if it is not in spec. You have a bench of very high quality equipment (rack full, all Tek too), as calibration tools. If the calibrator cannot get it in spec he may give it back to the factory floor or perhaps check and repair if he can. That is what makes a Tek so expensive. And that is where precision is achieved. The references and trimpots are just 10 cent little things you can get from anywhere, used to surprise me in the beginning, not 10 turns, no nothing like that. Bending of wires to the CRT to get 'in spec' on the bandwidth was normal too. So before you start on your jive of manufacturing 'precision' equipment, better look on how that is done.
In any other case your design sucks if it needs 1 in a thousand for every day stuff. So that is MY view and MY experience.
BTW the 3 $ multimeters from China I have, and I love those, have a similar trimpot in them. It is a MASS MASS MASS MANY MANY product, and I suspect a little Chinese girl twiddling at 1000 an hour on a test bench where they fly past her, The trimpots are so feeble and flexible mounted that I cannot imagine a robot hitting the slot in it. But I could imagine this person having a controlled screwdriver from some test point on the PCB setting the pot to the right value. Only limited by your imagination.
Thank you for reading
WTF am I writing this at 7:30 in the morning? :-)
On a sunny day (Thu, 26 Jul 2012 22:29:12 -0700) it happened Robert Baer wrote in :
adjusted byte
Impossible is a very flexible thing.
I hope you have high banddwidth by now, video is very interesting, not so much electronics, but more physics.
On a sunny day (Thu, 26 Jul 2012 22:25:12 -0700) it happened Robert Baer wrote in :
In color TV, and your 25 kV points to that, the beam current can vary between 0 and about 1.5 mA (maybe more). Stabilization of the HV (that comes from the horizontal output transformer) via a voltage multiplier, is normally done by looking at a lower voltage pulse from that output transformer. Its amplitude will decrease a lot with increasing beam current, so you can use it in a control loop.
In the old tube days a parallel stabilizer triode was used and a single phase tube rectifier.
But never ever in my life have I seen zeners over the 25 kV, that would be problematic as the power consumption is huge, if you send 1.5 mA at 25 kV into your zeners for a 'black' screen, than those zeners will dissipate 37.5 W. In reality more, as you have to pre-load those zeners. I recommend the voltage multiplier and feedback winding method...
via a voltage multiplier,
transformer.
it
tube rectifier.
problematic
for a 'black'
Or stock up on HV regulator tubes. They are still widely availibe and cheap, since there is little demand for them.
On a sunny day (Fri, 27 Jul 2012 02:45:40 -0400) it happened "Michael A. Terrell" wrote in :
via a voltage multiplier,
transformer.
use it
tube rectifier.
problematic
zeners for a 'black'
Yes, but then he has to put them in a clsed metal cage agaisnt roentgen radiation.
via a voltage multiplier,
transformer.
use it
phase tube rectifier.
problematic
zeners for a 'black'
radiation.
There should be a shield already - the same X-ray (Roentgen) radiation hazard consideration applies to the plasma regulator tubes.
-- Tauno Voipio
So......in other words, you concede?
Note: trimpots and THT may work in China but Made in USA (or Europe for that matter) products can only tolerate a minimum of labor. This is a real market and there are real products doing exactly what I describe. But they don't use crappy onboard uC references to do it, they use one with guaranteed specs.
Tim
-- Deep Friar: a very philosophical monk. Website:
On a sunny day (Fri, 27 Jul 2012 07:53:54 -0500) it happened "Tim Williams" wrote in :
No. Read again what I wrote.
PIC internal reference is not crappy at all. A lot better than the zeners you use in your voltage converter diagrams :-)
Fight fight fight... :-)
via a voltage multiplier,
transformer.
use it
phase tube rectifier.
problematic
zeners for a 'black'
radiation.
No, you don't. There are some types with enough lead to stop the radiation. At least in the US.
Zeners in my converters? Which ones?
I only use zeners for clamping and stabilization, never as a reference.
Even so, the lowly 1N5231B is rated for 2%, which is still better than your PIC. Are we done yet?
If you're referring to TL431, do read the datasheet some time: its recommended symbol may be a controlled zener, but it's actually a high-gain op-amp with +in internally connected to 2.50V at 2% or better tolerance. And it has to be used as such. Hence the compensation stuff around it.
I typically buy the -B versions, which are 0.5%. Anything better than that and I get a proper reference (< 0.1%, maybe by AD or LT). No need for a tedious adjustment step anywhere, domestic or in China.
Tim
-- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
In the Olden Days, they had corotrons, which used some gas mix and multiple stages, or field emission or something, to do the same job as a zener or gas reg tube, but higher. Which is what's being replaced here.
I guess the restoration sets in question were equipped with corotrons, which are a lot harder to come by than the triodes (e.g., 6BK4C for HV shunt reg, or 6HS5 et al. for pulse regulation), and converting them is out of the question for whatever reasons (e.g., it's not a reasonable facsimile of the original design, or it would require extensive modification). The desired solution is a "black box" can, which sits in the same space and does the same job.
So, a shunt triode isn't a bad idea -- it's what the manufacturers originally did anyway. But that may not be an acceptable solution for very picky restorations.
What was wrong with the MOSFET cascode? Put a TL/V431 at the bottom, maybe feed in a few extra mA from a lower voltage rail, and you're done.
You could also cascode a TL/V431 with a higher voltage transistor (or a 6C4) with a 6BK4C, to get extremely well regulated HV in nearly a single stage.
Tim
-- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
You can also trim the drive to the Horizontal Output tube.
Check; these 25KV Corotron(TM) tubes are about 1.5" dia and 6" long. "Converting" them does not take extensive modification; remove bottom so zener stack can be inserted, the positive lead feeding thru a hole drilled in the connector pin on the top; looks preserved. The dicey part is the insulation between the stack and the inside metal shell..
series
and
HV
without
Perhaps you need to be more creative in how you use the 431.
?-)
On a sunny day (Fri, 27 Jul 2012 15:06:23 -0400) it happened "Michael A. Terrell" wrote in :
radiation.
Type number? I KNOW US is heavy, but....
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