Several years ago I needed about 1.5 amps at 175 volts to power up my array of (16) B-7971 tubes.
Found on Ebay a very nice old Hewlett Packard model 395A adjustable power supply. It puts out 0 to 1.5 amps over a range of 0 to 320 volts DC. It is a 19 inch rack-mountable unit. It was in service at Los Alamos, NM at one time then sold as surplus. After receiving it, I opened it up and vacuumed out a layer of western desert fine red dust, cleaned it all up and put it in service here to light up my scrolling B-7971 array. Even contacted Agilent Technologies and found a guy there who copied off the complete manual for it and sent it to me. That is what I did when I needed a real power supply! :) Chuck Richards > > >---- Original Message ---- >From: [email protected] >To: [email protected] >Subject: RE: [neonixie-l] Re: High current 1.5A x150V power supply >design for 100 IN9s >Date: Wed, 10 Feb 2016 17:37:02 -0800 (PST) > >>All excellent points. >>Having been on the fixing end of this stuff but never design I never >really >>thought about the how's and why's of certain layouts. >>They just worked or they didn't. >>Electronic design engineer I am not. >> >>Though I am very well aware of just how dangerous electrolytics are >... >>having been responsible for letting the smoke out of them on various > >>occasions. >>Choosing cap's seems to be a black art. >> >>I think I need a pro. The link Jonathan F pointed too has opened my >eyes. >>Flyback is needed here I think. >> >>On Thursday, February 11, 2016 at 1:46:38 AM UTC+8, gregebert wrote: >>> >>> There's nothing inherently unsafe about non-isolated supplies; >like any >>> high-voltage project, you have to be careful about keeping >everything >>> properly insulated and follow minimum-spacing rules carefully. >>> >>> The most-dangerous item in a high-current supply is the >electrolytic cap. >>> You *must* handle all of these concerns >>> >>> - Extra margin for voltage-rating. I use 450V (500V when >possible) >>> caps for ~200V supplies. Higher voltage ratings also reduce >leakage >>> current. Caps designed for solar-energy inverters are perfect >because they >>> come in high-voltage + high temp + high ripple-current. >>> - Be very conservative with rms ripple-current, because it >directly >>> affects self-heating. Obviously you dont want any warm >components near your >>> capacitors. Remember: Lifetime is dramatically impacted by >temperature. >>> - You must have a discharge resistor; I even put a flashing >neon bulb >>> across my large caps to indicate they have dangerous voltage. >Larger >>> resistance values take longer to discharge, but they reduce >wasted energy >>> (heat) >>> - Series fusing. In case the cap fails, you want to blow a >fuse, not >>> the cap. The fuse must be a small as possible, and dont forget >the RMS >>> charging current is not sinusiodal. BTW, this fuse is for the >cap; it's >>> in-addition to the fuse at the AC input. >>> - Charging-current needs to be limited during power-up. For the >1.5 >>> amp supply, a 1500uF cap will have 10 volts of ripple at 50Hz >when using a >>> full-wave rectifier. I'd suggest a series charging resistor of >about 200 >>> ohms to charge at power-on, then 'shorting' the resistor with a >relay after >>> charging is done. >>> - Surge protection at the AC input. I always have a fuse on >both AC >>> lines, then a varistor and 0.01uF capacitor (for filtering hash >noise if >>> it's present). If your current is 'low' (which isn't the case >in this >>> design), adding series resistance to create an RC filter is a >big help, and >>> furthermore the resistors will act as secondary fuses if you >pick >>> low-enough wattage. >>> - Reverse-polarity protection diode. If you dont use a bridge >>> rectifier, be sure to put a protection diode across the cap. >BTW, a >>> bridge-rectifier gives you reverse-polarity protection down to >1.4V, >>> whereas a single diode is 0.7V. Polarized electrolytics caps >can be damaged >>> with as little as 1 volt of reverse voltage, so you may want to >add the >>> diode even if a bridge rectifier is used. >>> >>> >> >>-- >>You received this message because you are subscribed to the Google >Groups "neonixie-l" group. >>To unsubscribe from this group and stop receiving emails from it, >send an email to [email protected]. >>To post to this group, send an email to [email protected]. >>To view this discussion on the web, visit >https://groups.google.com/d/msgid/neonixie-l/2ac038a0-aadf-42ca-989c- >fb8b8fb93ca6%40googlegroups.com. >>For more options, visit https://groups.google.com/d/optout. >> $4.95/mo. National Dialup, Anti-Spam, Anti-Virus, 5mb personal web space. 5x faster dialup for only $9.95/mo. No contracts, No fees, No Kidding! See http://www.All2Easy.net for more details! -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. 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