High voltage diode blowing mysteriously
in [Design]
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From: m II on 6 Jul 2010 14:45 StickThatInMyAssAndSmokeArchie'sPecker wrote: > Better hope you never find yourself in one of my apertures. Not very much chance of that. Don't you remember that appendage was lost in your love tunnel during an unexpected onset of leprosy? I distinctly heard you say "Damn, I was just getting regular". ============================================ But I say to you that everyone who is angry with his brother will be liable to judgment; whoever insults his brother will be liable to the council; and whoever says, �You fool!� will be liable to the hell of fire. Matthew 5:22 http://www.photosforsouls.com/hells-fire-duncanlong181.jpg ============================================ father mike
From: Nunya on 6 Jul 2010 15:01 On Jul 6, 11:45 am, m II <c...(a)in.the.hat> wrote: > StickThatInMyAssAndSmokeArchie'sPecker wrote: > > Better hope you never find yourself in one of my apertures. Nice morph, idiot. Still a rifle scope has an aperture as well. Maybe you have the wrong impression (no maybe about it) You see, idiot boy... I do not want to be in one of your apertures, I want to give you a nice, small entry aperture that expands conically to an exit aperture of several inches, excavating all the sub-human scum mass contained within the cone. I do not expect you to have a clue as to what that really means. > > Not very much chance of that. You wouldn't know, and it would make the aperture before you either hear or see it, so you won't even know until you wake up naked in front of the Lord, to be judged for your abject failure as a man. >Don't you remember that appendage was > lost in your love tunnel during an unexpected onset of leprosy? You really do need to have that aperture applied to your abjectly retarded, sub-human mass. > I distinctly heard you say "Damn, I was just getting regular". This is Usenet, retard boy, You did not "hear" anything. Keep it up, retard boy. Show the world how truly pathetic you really are.
From: legg on 6 Jul 2010 22:07 On Mon, 5 Jul 2010 23:20:23 -0500, "Tim Williams" <tmoranwms(a)charter.net> wrote: >"legg" <legg(a)nospam.magma.ca> wrote in message news:6p7536hhm12k3oggp0dsj6te2b8556n7r0(a)4ax.com... >> If the currents are unbalanced, you may need freewheeling rectifiers >> to ground, before the choke, on both sides. > >Ah, interesting. > >The dead time voltages are near zero (give or take a small amount of squiggle), so it seems to be okay. > >Tim Coupled output inductors are useful, in reducing minimum load for quasi-regulated outputs - your -250V and 6V3 filament supply. There are leakage effects that have some regulation benefits, but will almost guarantee conversion frequency doubled reverse bias spikes at turn-off - so a kilovolt diode has no margin here. The negative rail, being quasi-regulated, will have the higher voltage when loading swings to the regulated rail. RL
From: JosephKK on 7 Jul 2010 01:24 On Mon, 5 Jul 2010 18:04:58 -0500, "Tim Williams" <tmoranwms(a)charter.net> wrote: >"Hammy" <spam(a)spam.com> wrote in message news:0qk336ptcj6mn9bso5omb6mu1l95ttgqp0(a)4ax.com... >> You need to take differential measurments. >> >> I plugged in some estimates based on an absouloute output voltage of >> 500V and they do indeed see 1.9KV. >> >> http://i48.tinypic.com/2ec3z89.png > >Well that's obviously wrong. The transformer only makes 300V peak output (600p-p, not counting LL), and it's obviously full wave, not half wave. The driver is clearly half bridge and the transformer ratio is clearly 1:4+4. >http://myweb.msoe.edu/williamstm/Images/Tubescope_Calc.png >These are my actual design constraints, actually, and the waveforms are very familiar indeed. Add some laggy parasitic C, and some springy LL, and you've got the real thing. The only difference between this circuit and the actual circuit is the center tap and split choke, which do not affect the simulation results, and serve only to split the resulting DC output in half, hence +/-250V. > >Tim And your line of thought goes to heck in a handbasket due to the inductor input filter! Put some capacitance right at the output of the bridge, 470 pf ought to do. I bet it cools off your snubbers too.
From: JosephKK on 7 Jul 2010 01:31
On Mon, 5 Jul 2010 00:12:55 -0700 (PDT), Nunya <jack_shephard(a)cox.net> wrote: >On Jul 4, 5:33 pm, Joerg <inva...(a)invalid.invalid> wrote: >> John Larkin wrote: >> > On Sun, 04 Jul 2010 15:28:01 -0700, Joerg <inva...(a)invalid.invalid> >> > wrote: >> >> >> Tim Williams wrote: >> >>> I have a high voltage power supply, >> >>>http://myweb.msoe.edu/williamstm/Images/Tubescope_Supply2.png >> >>> under reasonable load (140VDC link voltage; Vadj set for 230V output; 3A heaters, fractional mA at -2kV, 100mA at +230V, 35mA at -230V). It runs cool and smooth for about a minute (aside from the snubbers, which get quite hot), then suddenly the output drops dead and the current limit starts squealing. One of the negative output diodes is failing shorted. (Good thing the current limit keeps it from nuking the transistors.) >> >> >>> Until failure, the diodes run cool (aside from what heat they pick up from the snubbers). The waveforms show 120V overshoot, which is well within ratings (1000V diode with about 600V peak reverse). I can't imagine it's an avalanche thing, as the reverse voltage is low and, until failure, the diodes run cool. I'm still more confused that it's consistently the negative side diode (three have died so far), which is the lighter loaded side. >> >> >> I don't see any snubbers of clamps on the upper right transformer where >> >> it says 102T. >> >> >> BTW, it helps to turn on designators. TR1, Q5, R6, and so on. >> >> > TR? A transistor is Q. A transformer is T. >> >> > John >> >> Sir, yes, Sir! <clicking heels, saluting> >> >> On mil schematics that's the case but civilian ones are all over the map >> in that respect. You should see the new DIN or whatever standard WRT >> designators, it's the epitome of bureaucratic nonsense. Designators >> different for the same type of component and depending on its function. >> >> I just had one that said TR, another one XFMR. >> > And BOTH are incorrect designations. They can be used in item >descriptions (xfmr), but reference designators have an industry >standard >and your remark that they do not is noncorrect in all circles excpet >those >where some stupid dope like you refuses to use the industry >standard(s). >So, essentially you hang out in some stupid clics. Designators have >had variances based on device function. Diodes are a perfect example. > We see "D1" or "CR1", where "CR" was derived from "Cathode >Rectifier". You have a bit of hoof in mouth i see. CR was once used for Crystal Rectifier, a reflection of its solid state nature and variety of chemical compositions. Ever heard of copper oxide or selenium rectifiers? |