On Thu, 26 Jul 2012 22:20:37 -0700, Robert Baer <robertbaer@localnet.com> wrote:>Tim Williams wrote: >> "Robert Baer" <robertbaer@localnet.com> wrote in message >> news:IpqdnflGK8W9KY3NnZ2dnUVZ_uWdnZ2d@posted.localnet... >>> I need a 2-terminal device so tat i can put hundreds of them in =series>>> for 25KV. >>> So far, only one person divined that and his comment was trounced, =and>>> not politely. >> >> Like I said before (though possibly not in this thread), cascode some =HV>> MOSFETs. Only way you'll get the stability and noise you demand, =without>> stacking a bajillion 431's. >> >> Tim >> > Stacking 431s does work, but that cannot be used for this app as the=20 >standby or keep-alive current is too high. > And the other reference voltage parts cost too much (say 2.5V times=20 >10,000 times price each).Perhaps you need to be more creative in how you use the 431. ?-)
Zener noise / oscillations
Started by ●July 23, 2012
Reply by ●July 28, 20122012-07-28
Reply by ●July 28, 20122012-07-28
On a sunny day (Fri, 27 Jul 2012 15:06:23 -0400) it happened "Michael A. Terrell" <mike.terrell@earthlink.net> wrote in <P6KdnXvQBpove4_NnZ2dnUVZ_smdnZ2d@earthlink.com>:>> Yes, but then he has to put them in a clsed metal cage agaisnt roentgen radiation. > > > No, you don't. There are some types with enough lead to stop the >radiation. At least in the US.Type number? I KNOW US is heavy, but....
Reply by ●July 28, 20122012-07-28
On a sunny day (Fri, 27 Jul 2012 17:52:47 -0500) it happened "Tim Williams" <tmoranwms@charter.net> wrote in <juv64g$t9o$1@dont-email.me>:>"Jan Panteltje" <pNaonStpealmtje@yahoo.com> wrote in message >news:juu43l$fh0$1@news.albasani.net... >> PIC internal reference is not crappy at all. >> A lot better than the zeners you use in your voltage converter diagrams >> :-) > >Zeners in my converters? Which ones?ahum>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,Have not used that chip ever, unlike some here.>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.Keep dreaming.
Reply by ●July 28, 20122012-07-28
Robert Baer a �crit :> Jan Panteltje wrote: >> On a sunny day (Wed, 25 Jul 2012 20:06:05 -0700) it happened Robert Baer >> <robertbaer@localnet.com> wrote in >> <IpqdnflGK8W9KY3NnZ2dnUVZ_uWdnZ2d@posted.localnet>: >> >>> Jan Panteltje wrote: >>>> On a sunny day (Tue, 24 Jul 2012 23:39:15 -0700) it happened Robert >>>> Baer >>>> <robertbaer@localnet.com> wrote in >>>> <WeudnYHn_bcLCZLNnZ2dnUVZ_jOdnZ2d@posted.localnet>: >>>> >>>>> Tim Williams wrote: >>>>>> "Robert Baer"<robertbaer@localnet.com> wrote in message >>>>>> news:y4CdnbWbSZcVtpPNnZ2dnUVZ_rGdnZ2d@posted.localnet... >>>>>>> Yes, a TL431 is cheap but the minimal standing current is way above >>>>>>> what is needed. >>>>>> >>>>>> 1mA? TLV431 is 100uA and 1.240V, much improved. >>>>>> >>>>>> Tim >>>>>> >>>>> Range needed: 10uA-500uA. >>>> >>>> It is interesting to note that the PIC 18F14K22 is specified with >>>> FVR only running at: >>>> 1.8V 28 uA >>>> 3V 65 uA >>>> 5V 101 uA >>>> For a reference output of 1.024V >>>> >>>> I would think that if you put it into sleep mode, that would make >>>> your specs... >>>> Datasheet page 337 >>>> It is possible to send the Vref output to a pin in that mode AFAIK. >>> I need a 2-terminal device so tat i can put hundreds of them in >>> series for 25KV. >>> So far, only one person divined that and his comment was trounced, >>> and not politely. >> >> OK, so I did not see you mention 25kV @ say<100uA. >> That will not be easy with zeners. > * Tell me about it; seems almost all have a negative R region right > where i need to operate. > >> >> You also need to mention stabilisation factor in percent for example, >> for anybody to even think about it. > * What exactly do you mean by stabilization? > See below. > >> >> I could easily generate 25kV locally with a transistor circuit and >> even some feedback turns, without a bleeder on the whole HV. >> Any decent last century CRT solid state color TV does it that way. >> Zeners do not make that much sense here to me. > * This is a TV restoration project; ideally the looks are preserved. > *** > Have done some suggested testing of the 75V part and compared the > result to the same testing of the 68V part. > What i find interesting is that for negative resistance parts, the > (what i call) the "N" type where voltage goes down as current increases > (eg: Esaki or tunnel diode), it is very easy to get to oscillate; for > the (what i call) the "S" type where current goes down as voltage > increases (eg: Zeners with "switchback"), it is hard to make it oscillate. > The 75V part looks good, now i will chain some together.. >Maybe try a few avalanche rated mosefts? You'd have to test them... -- Thanks, Fred.
Reply by ●July 28, 20122012-07-28
Jan Panteltje wrote:> > On a sunny day (Fri, 27 Jul 2012 15:06:23 -0400) it happened "Michael A. > Terrell" <mike.terrell@earthlink.net> wrote in > <P6KdnXvQBpove4_NnZ2dnUVZ_smdnZ2d@earthlink.com>: > > >> Yes, but then he has to put them in a clsed metal cage agaisnt roentgen radiation. > > > > > > No, you don't. There are some types with enough lead to stop the > >radiation. At least in the US. > > Type number? > I KNOW US is heavy, but....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.
Reply by ●July 28, 20122012-07-28
On a sunny day (Sat, 28 Jul 2012 09:09:43 -0400) it happened "Michael A. Terrell" <mike.terrell@earthlink.net> wrote in <4qSdnUDuqewBeY7NnZ2dnUVZ_jKdnZ2d@earthlink.com>:> >Jan Panteltje wrote: >> >> On a sunny day (Fri, 27 Jul 2012 15:06:23 -0400) it happened "Michael A. >> Terrell" <mike.terrell@earthlink.net> wrote in >> <P6KdnXvQBpove4_NnZ2dnUVZ_smdnZ2d@earthlink.com>: >> >> >> Yes, but then he has to put them in a clsed metal cage agaisnt roentgen radiation. >> > >> > >> > No, you don't. There are some types with enough lead to stop the >> >radiation. At least in the US. >> >> Type number? >> I KNOW US is heavy, but.... > > > > But what?But lead tubes?>My tube handbooks are in storage and I haven't used a >shunt regulator in close to 40 years.I had a tube handbook, it was written by an old schoolmate, dunno what happened to it (or him after he was fired).>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.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. http://www.radiomuseum.org/tubes/tube_pd500.html http://www.youtube.com/watch?v=jGe0D1GdktA 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: http://www.noah.org/science/x-ray/stong/ 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.
Reply by ●July 28, 20122012-07-28
On Fri, 27 Jul 2012 19:38:01 -0400, Michael A. Terrell wrote:> You can also trim the drive to the Horizontal Output tube.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)
Reply by ●July 28, 20122012-07-28
On Sat, 28 Jul 2012 08:45:59 +0000, Jan Panteltje wrote:> On a sunny day (Fri, 27 Jul 2012 15:06:23 -0400) it happened "Michael A. > Terrell" <mike.terrell@earthlink.net> wrote in > <P6KdnXvQBpove4_NnZ2dnUVZ_smdnZ2d@earthlink.com>: > >>> Yes, but then he has to put them in a clsed metal cage agaisnt roentgen >>> radiation. >> >> >> No, you don't. There are some types with enough lead to stop the >>radiation. At least in the US. > > Type number? > I KNOW US is heavy, but....Europeon lookalike - PD500. -- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)
Reply by ●July 28, 20122012-07-28
On Thu, 26 Jul 2012 22:38:41 -0700, Robert Baer wrote:> no series > resistance selectable.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)
Reply by ●July 28, 20122012-07-28
On Thu, 26 Jul 2012 22:38:41 -0700, Robert Baer <robertbaer@localnet.com> wrote:>Fred Abse wrote: >> On Thu, 26 Jul 2012 13:02:58 -0700, Fred Abse wrote: >> >>> On Wed, 25 Jul 2012 20:50:26 -0700, Robert Baer wrote: >>> >>>> I have posted a 7CT1N curve tracer screen photo under the heading >>>> "ref:Zener noise / oscillations". >>> >>> Which 7000 series mainframe has a *red* phosphor? >> >> I forgot to ask: >> >> What zener? >> >> What voltage and current scales? >> >> What series resistance? >> >> I'd like to try that. >> > 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.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 Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
