Planning to build benchtop 500V tube PSU, help needed. - Page 1
Forum section: electronics / projects

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 11, 2018, 07:23:24 am
content: I've been planning to build a high voltage bench power supply for a while now, and I have come across the design linked in below.I want to make an old school tube based design, because tubes, and am hoping anyone can give me some pointers as to the design.Are there any modifications I should do to this one before I build it (or is there a better design I should make instead)?I assume there would be a few bits and pieces to update the design a bit since this was designed in the late 60's......As it is only going to be used for tube amps etc, it doesn't need laboratory PSU levels of ripple and regulation, but the better it is, the better it is, until we hit diminishing returns..Let me know what you think!

author: 001
author_rank: Super Contributor
timestamp: December 11, 2018, 07:37:40 am
content: look my old treadit is not possiblesimply buy one

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 11, 2018, 07:38:57 am
content: What do you mean it can't be done? Did you see the attachment?

author: 001
author_rank: Super Contributor
timestamp: December 11, 2018, 07:43:39 am
content: Quote from: TERRA Operative on December 11, 2018, 07:38:57 amYeathis is common regulator circuit of sixtiesQuote from: TERRA Operative on December 11, 2018, 07:38:57 ambut it is not lab PSU since no any current controlMany peoples here told me keep HV away

author: Moshly
author_rank: Regular Contributor
timestamp: December 11, 2018, 07:48:29 am
content: I'd get an old faulty Tek 5xx Scope from ebay (as long as the transformer works) and make something like this ->https://evilscienceaudio.com/repairs-restorations/tektronix-engineering-power-supply/

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 11, 2018, 08:29:58 am
content: Quote from: 001 on December 11, 2018, 07:43:39 amThat's ok, as it is just for powering tube amplifiers during testing and repair etc. No need for super accurate voltages etc.Quote from: Moshly on December 11, 2018, 07:48:29 amHoly moley, that is one unit of a PSU.... I'll have a look at it, but it may be more than I need.Overkill never hurt anyone though, except my wallet....

author: Cyberdragon
author_rank: Super Contributor
timestamp: December 11, 2018, 08:35:57 am
content: I don't see any problems with that circuit other than being a bit cheeky. It shouldn't have too much ripple as C4 appears to be some sort of humbucking. However, you will not get too much current either as those are just jellybean audio tubes that they've ganged up (180mA best case all tubes new). I would look into getting one big tube to replace all the little ones, what they're doing is a bit naughty (250V rated tubes).

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 11, 2018, 08:40:42 am
content: What sort of tube would you recommend? I have access to more than I know what to do with down at Akihabara...Maybe there are some of the bigger tubes that I could gang up a couple?

author: 001
author_rank: Super Contributor
timestamp: December 11, 2018, 08:43:05 am
content: Quote from: Cyberdragon on December 11, 2018, 08:35:57 amWrong waysince internal PSU impedance is not small, parasitic feedback in thecircuit under testis sufficientfew pass tubes eliminate problem

author: tautech
author_rank: Super Contributor
timestamp: December 11, 2018, 08:53:17 am
content: Quote from: TERRA Operative on December 11, 2018, 08:40:42 amA 5Z4 is a common one and can handle 100mA which is all you need unless you're gunna make high power amps.A CLC filter was a common smoothing circuit 'back in the day' but decent HV chokes are not as easy to find as they were. Getting down to a couple of volts ripple isn't that hard to do.

author: Wolfgang
author_rank: Super Contributor
timestamp: December 11, 2018, 11:14:56 am
content: Hi,have you seen that there are books full of PSU designs for tube audio, like this one:Valve Amplifiers, by Morgan Jonesor have a look at this thread of EEVBlog:https://www.eevblog.com/forum/projects/overhauling-high-voltage-vacuum-tube-(valve)-power-supply/msg389145/#msg389145play safe, have fun.Wolfgang

author: David Hess
author_rank: Super Contributor
timestamp: December 11, 2018, 07:01:47 pm
content: For practical reasons I would use silicon diodes to replace the rectifier tube and zener diodes to replace the voltage reference tube.The same configuration with a single pass transistor and single transistor error amplifier was common in early power supplies.

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 14, 2018, 10:55:05 am
content: But practical is less fun!I'm looking at the C-L-C filter section at the moment, and 8uF, 600V capacitors are a bit hard to come by... How much leeway do I have to substitute values (and the 10H choke too)?

author: 001
author_rank: Super Contributor
timestamp: December 14, 2018, 11:02:18 am
content: Quote from: TERRA Operative on December 14, 2018, 10:55:05 amit is wery difficult at XXI centuryDo You Really NEED 500V output?

author: Wolfgang
author_rank: Super Contributor
timestamp: December 14, 2018, 03:18:02 pm
content: You need two 450V caps in series with equalizing resistors. No big deal.

author: Emo
author_rank: Regular Contributor
timestamp: December 14, 2018, 03:50:15 pm
content: Be careful while selecting the regulator tubes. Often tubes have a maximum voltage between cathode and filament. In push-pull configurations special versions were produced like the FAMOUS EL84 and the EL86. Both the same specs except for the cathode to filament voltage.An other way of solving this is to have a floating filament supply specific for those regulator tubes. Made one myself decades ago with regulator valves. Still workingEric

author: Wolfgang
author_rank: Super Contributor
timestamp: December 14, 2018, 04:52:51 pm
content: Hi, agreed the mximum voltage between cathode and filament is an issue.For the pass valve, the heater should float around the output. I tried two ways:- pass valve heater sitting at the output voltage in a center tapped heater transformer- Make the whole regulator floating. This automaticall solves the problem above.You could use valves with a higher maximum voltage between cathode and heater, like the PL519. Here you have 250V, the EL84 has 100V only.Much funWolfgang

author: 001
author_rank: Super Contributor
timestamp: December 14, 2018, 04:59:09 pm
content: Quote from: Wolfgang on December 14, 2018, 04:52:51 pmCan You illustrate it with tube circuit?

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 15, 2018, 06:08:15 pm
content: Quote from: Wolfgang on December 14, 2018, 03:18:02 pmAh yep, I completely missed that one. Easy enough to do and caps are cheap.Quote from: Emo on December 14, 2018, 03:50:15 pmQuote from: Wolfgang on December 14, 2018, 04:52:51 pmI managed to get my hands on a bunch of 6005W tubes for the regulator tubes (Basically a shock and vibration resistant version of the 6AQ5), are they safe to use as per the original design, or is there something (like the PL519 or similar) that would be better to use instead? The 6AQ5/6005W has a max cathode to heater voltage rating of 200VI'm also interested in how I would make the reguator floating too.

author: 001
author_rank: Super Contributor
timestamp: December 17, 2018, 10:15:28 am
content: 6aq5 so crappytry TV tubeit is rugged and cheap

author: Wolfgang
author_rank: Super Contributor
timestamp: December 17, 2018, 12:57:19 pm
content: Hi,I will post a floating design in a few days, sorry for the delay.

author: Dave
author_rank: Super Contributor
timestamp: December 17, 2018, 02:36:34 pm
content: Quote from: 001 on December 11, 2018, 07:43:39 amYes, they toldyouto stay away from HV, because they don't want you to kill yourself. Nobody wants the burden of giving you a design and then finding out that you managed to electrocute yourself with it, because you lack the knowledge and experience to work on such a dangerous circuit.The fact that you don't demonstrate the knowledge required for pulling off this sort of circuit, doesn't mean that everyone should avoid them.At first glance, OP seems competent enough for working on this sort of circuit, which is exactly why you don't see people jumping into the thread trying to convince him to keep clear of HV.

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 17, 2018, 03:26:46 pm
content: Quote from: Dave on December 17, 2018, 02:36:34 pmEither that, or the electricians callouses offer me enough insulation resistance to keep me relatively safe.

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 17, 2018, 04:05:00 pm
content: Quote from: 001 on December 17, 2018, 10:15:28 amDo you have any suggestions? I'm not as well versed in tube substitution as I am with silicon...

author: 001
author_rank: Super Contributor
timestamp: December 17, 2018, 04:50:59 pm
content: Quote from: TERRA Operative on December 17, 2018, 04:05:00 pmTry thishttp://tdsl.duncanamps.com/show.php?des=6KG6U still not say how much mA do You need

author: Wolfgang
author_rank: Super Contributor
timestamp: December 17, 2018, 04:58:07 pm
content: ... in European terms this is the PL519, a powerful sweep often used in linear HF amps.Quite robust.Please tell how many mA you need at 500V, because this determines the size of the pass tube(s).

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 17, 2018, 04:58:41 pm
content: Cool, I'll check it out.The article in the OP rates the PSU at 100mA, but the transformer I'll use is good for 200mA (Hammond 374BX)

author: Wolfgang
author_rank: Super Contributor
timestamp: December 17, 2018, 05:24:11 pm
content: ... OK, so we have to live with 3 tubes (PL519 assumed). One tube can dissipate ca. 35W, assuming we have about 700V of raw rectified voltage we dissipate 70W at 100mA into a short circuit. 3 tubes are safe, with 105W maximum. You will need a fan anyway ...

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 17, 2018, 05:31:29 pm
content: Is it easy to add a few more tubes to get closer to the 200mA rating of the transformer, or is there a limitation that caps it at 3 tubes?

author: schmitt trigger
author_rank: Super Contributor
timestamp: December 17, 2018, 05:34:51 pm
content: I have seen HV PSUs built with a 6550 tube, far more powerful than a 6AQ5.The 0A2 regulator tubes have a really nice glow, hope that you can find them. Last time I checked they were in short supply...but you can always go to Akihabara.EDIT: There is a note on the schematic:SD1 and SD2 are shown in reverse polarity. Mount opposite way.The way I see it, the diodes are oriented correctly, they are generating a negative voltage for V4's grid. Anyone has a different opinion?

author: Wolfgang
author_rank: Super Contributor
timestamp: December 17, 2018, 05:43:39 pm
content: Quote from: TERRA Operative on December 17, 2018, 05:31:29 pmIf your transformer is rated for 200mA, this means that the *rectified* current you can draw is about 60% of that. The reason is that- the rectified current is not sinusoidal, but comes in shorter, high amplitude pulses- the pulses are not in phase with the voltage.so the magnetizing effect is very different from a resistive load and that puts more stress on the magnetics.Result: your 200mA transformer makes a good 100mA PSU with some safety margin.Recommended literature: Horowitz and Hill Art of Electronics CH. 9

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 18, 2018, 04:46:39 am
content: Quote from: schmitt trigger on December 17, 2018, 05:34:51 pmI'll take a look at those 6550 tubes, I'll check to see what they are worth over here.It's funny, some common tubes in the States or more often in Europe are hard to get here, but others are super easy. Bit of pot luck sometimes, but substitutes can almost always be found.I'm about to go on holiday, so it'll be a few weeks before I can make another trip to Akihabara or heat up a soldering iron...I managed to get myself two 0A2 tubes for $15 the other day, so I'm all set there.(See the attached pic)And yep, I saw that note re. the diodes.I'm redrawing the schematic and I got that detail.I'd be interested in what others think about their orientation too.Quote from: Wolfgang on December 17, 2018, 05:43:39 pmAh-ha, makes perfect sense. I'll dust off my copy of AoE and take a closer look.Look at me, doing all this learnin'

author: schmitt trigger
author_rank: Super Contributor
timestamp: December 18, 2018, 02:37:02 pm
content: Since you will be using this supply to test and prototype tube circuits, you may want to add a pair of 6,3 volt filament supplies.The way I would do it is with a transformer with dual independent secondaries, such that you can wire them in parallel, series or use them independently.That would complete your project!EDIT: And don't forget the NEON indicator lamps. No LEDs please! I would use one as the main AC indicator, and another as the DC output enabled.Goes without saying that the meters should be analog.

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 18, 2018, 04:56:23 pm
content: Yep, I got some 90mm round analogue gauges on the way, and a big red incandescent panel lamp for the 'output on' and an orange neon for 'power switch on'. Old school all the way!Good idea on the 6.3v, the schematic shows the 6.3v for the internal tubes as being broken out to the front panel, but I think your idea is better for isolation and decoupling.I'm sure I can find an appropriate transformer on a shelf somewhere in Akihabara.

author: 001
author_rank: Super Contributor
timestamp: December 19, 2018, 07:43:39 am
content: Do You choose flying regulator schematic?

author: 001
author_rank: Super Contributor
timestamp: December 22, 2018, 11:14:52 pm
content: Quote from: Wolfgang on December 17, 2018, 12:57:19 pmAny news? PleaseBest Wishes

author: Wolfgang
author_rank: Super Contributor
timestamp: December 23, 2018, 01:14:50 am
content: Hi,I know I am late, but the upcoming holidays dont leave so much time for my hobby.Anyway, I would like to prod along the schematics in my website below:https://electronicprojectsforfun.wordpress.com/power-supplies/high-voltage-lab-power-supplies/a-250v-150ma-variable-linear-power-supply/This is a true floating design that worked very well (using semiconductors only).Your PSU has some extra requirements:- no silicon, glass only - IIRC one of your last comments.- voltage setting from 0 to 500V- amps up to 100mA- foolproof, robust, all components run safely below their maximum ratings.Consequences are:- a lot of transformers for the aux voltages plus the heaters (alternative is a custom made transformer for everything in 1 core)- data will be not as good as the semiconductor design (ripple rejection, stability, out voltage accuracy, ...) .It will be perfectly usable for tube circuits, however.What holds me up the most is getting useful SPICE models of the tubes I wanted to use.I have started a webpage showing what has been done so far at:https://electronicprojectsforfun.wordpress.com/power-supplies/high-voltage-lab-power-supplies/an-all-tube-500v-100ma-regulated-power-supply/Nice holidaysWolfgang

author: TERRA Operative
author_rank: Super Contributor
timestamp: December 23, 2018, 03:18:18 am
content: Wow, awesome work so far! No rush, I'm on holiday too.A couple silicon diodes in the design would be ok if absolutely necessary, as the original schematic has a few, but transistors are too new-fangled for the 60's style.I can get a custom transformer made, but if it can be made with an off the shelf transformer/transformers, it'd make it much easier for others to make their own.I think the simpler, the better. My use case for this is only for powering tube based projects, so looser output parameters for ripple, regulation, etc are fine.

author: 001
author_rank: Super Contributor
timestamp: December 23, 2018, 03:47:52 am
content: Quote from: Wolfgang on December 23, 2018, 01:14:50 amAwesome work!Looks very interesting. Can You tell how it works and why so many TL431 used?ThanxUPD : Sorry. Is CNY17 wiring correct at diagram? Is it good idea change 1000pF caps with 100pF? ThanxUPD2: What the usage difference with Yours awesome second projecthttps://electronicprojectsforfun.wordpress.com/power-supplies/high-voltage-lab-power-supplies/a-500v-30ma-variable-linear-power-supply/UPD3: Sorry for my delight and curiosity! Can You post diagram forhttps://electronicprojectsforfun.wordpress.com/power-supplies/high-voltage-lab-power-supplies/a-dual-120v200ma-linear-power-supply/andhttps://electronicprojectsforfun.wordpress.com/power-supplies/high-voltage-lab-power-supplies/a-275v-50ma-fixed-linear-power-supply/?UPD4: Does You use supressor diode like reference voltage sourse here?https://electronicprojectsforfun.wordpress.com/power-supplies/high-voltage-lab-power-supplies/a-1kv-50ma-linear-power-supply/Happy Christmas too!

author: coppercone2
author_rank: Super Contributor
timestamp: December 23, 2018, 10:11:36 am
content: Quote from: David Hess on December 11, 2018, 07:01:47 pmcareful making parts choices because of heat. I think mr. carlson measured those tube regulators to be something like 90ppm/c and they worked better then a zener diode as a regulator in the tube chassis (as a mod). he warned about this.I would agree with the silicon diodes.

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 07, 2019, 06:02:47 pm
content: Quick bump to let you guys know this is still happening...Got pretty much all the parts needed (pending final tube choices) except the enclosure (which I'll choose once I know the size I need) and the power transformer and 12H inductor, which I can get from Digikey.Transformer -https://www.digikey.com/products/en?keywords=hm5128-ndInductor -https://www.digikey.com/products/en?keywords=hm4779-ndProblem is that after the Christmas expenses (airfares and all), I just blew this months allowance on a Tek 577-177 curve tracer, so I'll have to wait a bit to save up my pennies for those last bits.Anyway, here's a pic of the stuff I have so far.

author: coppercone2
author_rank: Super Contributor
timestamp: February 08, 2019, 03:00:43 pm
content: How much cooler does the vacuum insulated part of the tube get when the tube is cooled from envelope reradiation?Is it possible to measure temperature of the structure with a built in rtd to regulate heater power rather then to cool the tube?

author: ArthurDent
author_rank: Super Contributor
timestamp: February 09, 2019, 03:32:53 am
content: I’ve made some adjustable D.C. power supplies in the past using triodes as the pass element. On the larger supplies I used 6080WA or 6336 tubes. Here are some photos of a small 150-250VDC 100Ma supply I made ages ago that worked pretty well.What I’m using now is an electrophoresis power supply made by Bio-Rad that is somewhat similar to the one pictured below. These sell on eBay generally for less than $100. The one pictured has 2 voltage ranges of 250/500VDC and 2 current ranges of 50/500Ma. I needed one a little different so the one I bought has digital meters and goes up to 1Kv.

author: 001
author_rank: Super Contributor
timestamp: February 09, 2019, 10:12:27 pm
content: Quote from: ArthurDent on February 09, 2019, 03:32:53 amThanx for great info!Can You post schematics of this units or correct model numbers to google it?

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 10, 2019, 02:29:13 am
content: Quote from: ArthurDent on February 09, 2019, 03:32:53 amLooks cool!Don't tease us though! You got any schematics?

author: ArthurDent
author_rank: Super Contributor
timestamp: February 11, 2019, 01:17:35 am
content: When I made my 150-250VDC 100ma power supply I was trying to use parts I had in my junk box while still making a good regulated power supply. The case was from a military surplus magnetic amplifier and the case was the only part of that unit that was useful to me. I didn’t have one transformer that would work but I did have 2 identical smaller transformers that would fit perfectly in the back part of the case and give me the voltages and current I was looking for if I wired the HV windings in parallel. I did buy new meters and to give you an idea how old this is, I bought them from Lafayette Radio Electronics (kind of like Radio Shack) who went out of business in 1981! The circuit I used was one I modified from one I saw in an HP manual from about that time period.The voltmeter was modified to have an expanded range by using a 150V Zener and using a series resistor to make the meter really read 0-100 volts and then marking the dial to read 150-250 volts. If you’re wondering why there is a 1N4007 between the output and the meter, that is to prevent meter damage if the output somehow dropped to zero, effectively putting 150 volts on the meter in the reverse direction. The milliamp meter is the same basic movement as the voltmeter with the series resistor removed and a shunt resistor in parallel and the scale marked in Ma.One of the transformers 6.3 volt windings is used for the heater supply for the tubes and not referenced to ground to eliminate any heater to cathode voltage problems. The other 6.3 volt winding is connected to terminals on the back of the case to power tube heaters in devices I might be constructing.The capacitor from the supply output to the pot wiper eliminates the D.C. component but sends the outputs a.c. ripple voltage unattenuated to the error amplifier. Instead of using a 5651 gas reference tube like the original design I used a 82 volt Zener that gets its supply voltage from the regulated output. It feeds the reference voltage to the error amplifier through the triode section of the 6U8A used as a cathode follower. Where I didn’t use the 5651, the triode might not be needed and the Zener could probably supply enough current to be connected between the error amplifier cathode and ground, then I could replace the 6U8A with just a 6AU6 pentode. The 6BX7 has a maximum plate voltage rating of 600VDC so it is used within its specs.The HV rectified output from the two 1N4007 diodes is connected to the two 40 mfd electrolytics through a 10 ohm resistor that lessens the surge current and is also an emergency fuse. The two deck power switch is three position non-shorting and in the off and standby positions there is a 6.8K resistor connected from the two 40 mfd electrolytics to ground to safely discharge them. This capacitor has a 500 VDC rating because with no load there is about 450 volts on this capacitor. When the switch is in the operate position the 6.8K drain resistor is switched off and the HV center tap is connected to ground and the output is present.I didn’t have a schematic so I had to trace it out and that took me a while but here it is. Hopefully I didn’t miss anything.

author: Circlotron
author_rank: Super Contributor
timestamp: February 11, 2019, 01:31:41 am
content: For the front end I'd suggest a voltage doubler with two 400VDC caps in series. Big ones are very available nowadays. Depending on the cap size you may not even need to use a filter choke. Silicon diodes of course. And seeing the transformer would only need a single winding you have lots more to choose from!TV horizontal output tubes might be a good choice for the series pass reg, depending on price of course. They can have relatively low voltage drop when fully on.

author: Sylvi
author_rank: Regular Contributor
timestamp: February 11, 2019, 03:51:52 am
content: HiThe supply linked by the OP is not good for testing tube power amps as it only has 100mA. Preamps okay. A 10W amp with 10k OT primary will tax this PSU. A typical 50W amp with 4k load needs 300mA peak. A "dead" amp usually has a PSU and in most cases the thing is not dead is the PT. Repair and troubleshooting must be handled with common sense.What do you actually want to do?If you are building tube amps, they have a matched PSU, which you build and test first and always power new builds or suspect amps through a Power Limiting Safety Socket - light bulbs not variac.500V electrolytic caps are not a problem to acquire, just look at Digikey or Mouser. If you need higher than 600V, you have to either place caps in series with parallel bleeder resistors to enforce voltage sharing, or use plastic caps. You can get high values at high voltages in plastic, as they are used for DC links between incoming PSUs and point-of-use regulators. They are quite compact considering they have esssentially unlimited life expectancy.Unless you really want to build the tube PSU for fun or experience, there is no benefit to it being tubes versus solid-state. About the only benefit tubes offer is that they do not need heat sinks although they still need heat to be removed to be reliable.

author: 001
author_rank: Super Contributor
timestamp: February 11, 2019, 07:42:57 am
content: Any news? I`m electrified with this tread

author: schmitt trigger
author_rank: Super Contributor
timestamp: February 11, 2019, 04:42:14 pm
content: Arthur:Two thumbs up for your supply design!No, three thumbs up.I would only have kept the gas regulator tube instead of the zener, because, you know...........the nice glow.But I understand the choices you made. Zeners were less expensive than gas tubes, were less prone to motorboating, and back in those days having "hybrid" circuits were considered the path forward.The same can be said of the 1N4007 diodes versus -let's say- a 5U4.Thanks for taking the time to share your circuit.

author: 001
author_rank: Super Contributor
timestamp: February 11, 2019, 10:08:08 pm
content: Great workQuote from: ArthurDent on February 09, 2019, 03:32:53 amWhy? Can You post Biorad schematics?

author: ArthurDent
author_rank: Super Contributor
timestamp: February 12, 2019, 01:16:15 am
content: The Bio-Rad power supply I have is a complex microprocessor based switching power supply and even if schematics were available it would be basically impossible to duplicate it. As you can see from the photo of its LCD screen below it displays a lot of info and has timers and open circuit protection among other neat features, some of which are only applicable to its original use. A lot of the parts are not off the shelf items and the firmware would not be available. It is nice to be able to see the output voltage, current , and wattage all on one screen.While all this discussion of regulated supplies is interesting, I don't really think one is necessary because no audio amplifier I’ve seen needed one to operate. The output stages are generally push-pull and quite tolerant of power supply ripple and varying supply voltage. The drain of the previous stages is generally a few milliamps at a lower voltage which is easy to obtain and filter from the raw HV feeding the output stage. There is nothing wrong with making or buying an adjustable regulated supply but the one you showed and the small old one I have just wouldn't be suitable for your application as others have pointed out because of the limited current output.As to a suitable 300-400VDC max supply at up to 400Ma, it would probably be best to buy one and there are a lot of them on eBay similar to the type I bought but you're taking a chance on anything you buy, guessing if it will work for what you want.

author: 001
author_rank: Super Contributor
timestamp: February 12, 2019, 05:35:46 am
content: Quote from: ArthurDent on February 12, 2019, 01:16:15 amYea it`s really meaninglessAnd what about this analog beauty? I can`t google schematic for it

author: gbaddeley
author_rank: Regular Contributor
timestamp: February 12, 2019, 07:03:58 am
content: EL34 PL509 PL519 or 807, in parallel to get enough current & power handling, possibly triode connected

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 13, 2019, 04:34:00 am
content: Well, regarding transformers, I can get custom transformers wound here in Japan for a not tooo ridiculous price, so getting a 750V CT transformer wound with more current capability should be doable.I'll have to inquire what the cost will be but maybe I can get one rated to 500mA output or so.

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: February 13, 2019, 06:53:09 am
content: TERRA Operative:What's the big deal? Don't listen to the nay-sayers. If you can get the transformer you want then that's the biggest problem out of the way. All the rest is small stuff. But study the power supplies that the Tek guys put into the 500-series scopes as there are many lessons on efficient, high quality design there. I did here:https://www.instructables.com/id/Tube-Power-Supply/Admittedly the power transformer is from one of those scopes since I couldn't find a suitable one otherwise (and I, as well, was trying to build it from junk-box stuff, cheapskate that I am) but it serves very well. I stole the basic fundamental circuit for the HV section from the old scope and much of the -100V regulator from there as well and all the rest is mine. Its about 8 years old now and hasn't made a room full of smoke yet so I'm thinking it can't be so bad.Anyway, there is no problem with several pass tubes in parallel as long as they are halfway-well matched.I like the idea from your original schematic that allows the output to go to zero but I doubt that less than 50V is often useful, the LV tube enthusiasts notwithstanding.

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 13, 2019, 07:27:59 am
content: Ha yeah.I just want to build a tube based PSU for fun that I can use for building more tube stuff. The key word is 'for fun'...Like I don't care if it isn't gold standard efficient or hasn't got perfect mV level regulation, it's for prototyping valve circuits which don't care about that stuff anyway, just so I can try out tube stuff without having to build a power supply every time.I want to do it old school for old school sake and *for fun*I think I might just drop this thread and build it myself as I feel like it, there's too many wildly different opinions and naysayers here telling me to just buy some premade unit, completely missing the point of this DIY thread to start with.

author: TimFox
author_rank: Super Contributor
timestamp: February 13, 2019, 06:20:34 pm
content: A bit of my history building a simple tube regulator for a theremin (fixed 250 V output).I used a triode-connected 6Y6GA as the pass tube (low voltage drop) with a 6SH7 pentode error amplifier and a 0A3 75 V reference. The first build had a high frequency (roughly 70 MHz) parasitic oscillation, which I cured with a stopper resistor between the 6SH7 plate and the 6Y6 grid. Thereafter, I was paranoid about oscillation, and looked carefully at the output. The 120 Hz ripple was acceptable, but I found a similar amplitude line-synchronous component at precisely 10 Hz. I futzed around with the circuit near the 6SH7 plate, but only the amplitude changed—the frequency remained 10 Hz. While I was going crazy, my wife suggested that maybe I was picking up something, rather than an oscillation. I disagreed, since the only two things powered on were the oscilloscope and the soldering iron. Shutting the iron off removed the 10 Hz signal. The soldering station and DUT were both connected to the bench outlet. Apparently, the servoed soldering station at idle, with a zero-crossing switch, was in a limit cycle at 10 Hz, synced to the 60 Hz line. This must have modulated the heater of the 6SH7 and put a 10 Hz component into its input offset. A dual triode diff amp would have had less response to this heater variation.

author: 001
author_rank: Super Contributor
timestamp: February 23, 2019, 10:17:00 pm
content: hiHow are You? No posts for a long time

author: Wolfgang
author_rank: Super Contributor
timestamp: February 23, 2019, 10:32:23 pm
content: Hi,sorry for no progress, but still searching the web for some realistic tube SPICE models.Wolfgang

author: TERRA Operative
author_rank: Super Contributor
timestamp: February 24, 2019, 12:42:09 am
content: I'm still around.I've just been waiting for parts for multiple other projects, sorting through a cubic meter of electronics junk of mine I had shipped over from storage in Australia, finishing some other stuff, work and real life, etc etc.I might end up getting that custom transformer I mentioned previously made one day, once a few other things on my todo list are done (SWMBO keeps adding stuff to the top of the todo list, as usual.)

author: KD4CCF
author_rank: Contributor
timestamp: February 27, 2019, 02:10:58 pm
content: For vintage stuff, it's often better to buy then recreate.Check out Heathkit IP-17 and IP-32 power supplies on ebay.Attached is schematic of IP-32 which uses two 6L6 tubes for regulation.

author: schmitt trigger
author_rank: Super Contributor
timestamp: February 28, 2019, 02:48:23 pm
content: *Interesting* that the Heatkit design incorporates solid state diodes for the main DC bus, but has an 6X4 to supply the regulator tubes.Why would they do so? Why not replace the 6X4 with solid state diodes also?

author: duak
author_rank: Super Contributor
timestamp: February 28, 2019, 08:59:06 pm
content: One possibility why Heathkit used a 6X4 was that it delayed and/or softened the voltage rise on the regulator tubes. This could perhaps prevent the output voltage from going wild or from exceeding some voltage or current spec on some part during startup.Another is that 6X4s were cheaper than silicon rectifiers. The main rectifier was silicon because it saved power and reduced dissipation. It was cheaper because a separate 5 V winding was not needed for a thermionic rectifier's heater. I see that a voltage doubler was also used, so probably two thermionic rectifiers and two heater windings would have been needed.Cheers,

author: schmitt trigger
author_rank: Super Contributor
timestamp: March 01, 2019, 12:55:31 am
content: I believe that you are correct in both counts.However, I can see from the schematic that the main power switch has a standby position.Which presumably would be used to allow for the heaters to warm up prior to applying the main B+.Still, the slow warm up of the 6X4 would have prevented an incorrect start up procedure.

author: 001
author_rank: Super Contributor
timestamp: March 01, 2019, 07:12:13 am
content: Quote from: KD4CCF on February 27, 2019, 02:10:58 pmThis is normal only for US customers.Abroad, we can build a new one for the cost of delivery

author: 001
author_rank: Super Contributor
timestamp: April 08, 2019, 03:26:15 pm
content: Quote from: Wolfgang on February 23, 2019, 10:32:23 pmHow are You?

author: Wolfgang
author_rank: Super Contributor
timestamp: April 08, 2019, 05:13:50 pm
content: Hi,I got some models now (PL519 with grid currents) but they need to be tried out before I can recommend them.Some other tasks got in the way as well, so I apologize for the delay.regardsWolfgang

author: artag
author_rank: Super Contributor
timestamp: April 10, 2019, 09:13:46 pm
content: I've got a Kepco HB525 similar tohttps://www.georgia-market.com/LaGrange-/Electronics-/Kepco-hb-regulated-dc-power-supply-HB4AM.asp(not that actual one, it's not my advert) which is probably a pretty decent commercial example of this sort of thing. I can copy the schematic if useful, as Kepco kindly sent me a free copy of the manual (5* for Kepco !). 500V, 500mA, 0.01% line & load regulation, 1mV ripple, 2 x 10A aux heater supplies.The only downside (ok, apart from the weight, it's pretty much 100% transformium) is that it's supposed to have 5 GE 7581 tetrodes as the output devices. These, together with similar like the KT66 are prime audio valves and so rather expensive. I currently have a couple of battered 6l6 in there which keeps it well below rated output.So I really want to find some good quality 7581 equivalents which are, for whatever reason, disliked by the golden ear brigade. Maybe russian ? Or I could try substituting some suitable FETs but that's heresy, right ? Any suggestions ?

author: schmitt trigger
author_rank: Super Contributor
timestamp: April 10, 2019, 09:20:15 pm
content: At least it doesn't require any NOS genuine W-E 300B tubes.https://www.ebay.com/itm/ONE-Western-Electric-300b-NOS-1940S-Pre-WWll-production-FREE-S-H-ANYWHERE/142976348376?hash=item214a0df0d8:g:NWsAAOSwIrVbT8jG

author: chris_leyson
author_rank: Super Contributor
timestamp: April 10, 2019, 09:48:14 pm
content: There is always this monsterhttp://www.pmillett.com/HV_bench_supply.htmwith 807's !!

author: romhunter
author_rank: Regular Contributor
timestamp: April 15, 2019, 07:17:59 am
content: Quote from: chris_leyson on April 10, 2019, 09:48:14 pmI'm just suprised no one mention this design. I've been collecting parts to make it for a year. Just a few relays and a choke to go. 807's are cheap, those error amp tube and voltage reference tube can also be source (new tube, thank to Ukraine manufacturer).And there's another design:https://www.novotone.be/projets/alimentation-ht-de-laboratoire-gamme-de-50-a-450-v-500-ma, this one does not use any tubes.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 15, 2019, 11:06:38 am
content: the two previous posts are nice projects ...you had the isco 493 and 494 hacked modded on the web ... a thread there :https://www.diyaudio.com/forums/tubes-valves/81992-isco-494-a-2.html

author: H713
author_rank: Regular Contributor
timestamp: June 07, 2019, 06:25:37 am
content: Nice project- I'm (very slowly) designing a purely solid state power supply (but to be used for the same purpose) simply do to space requirements. But I will say- doing it with tubes is easier, I just have space limitations.If you want to goreally1970s with this, you could minimize how much heat is dissipated in the pass tubes by using a variac that is controlled by a servo motor depending on your output voltage and current to minimize drop across the series pass elements. Where I work we have some power supplies that can do up to 800A at 200V. They use 21 (its 3-phase) variacs (big ones) controlled by a sort of servo motor to keep the (something like 260) liquid-cooled pass transistors in their safe operating area. Something like this on a smaller scale could work nicely, although it is a bit crude.If you're looking for a power transformer, I've used these Antek toroidals and found that they're pretty hard to beat for the money. Making them look nice on top of a tube amp can be a bit of a pain, but if you put it in a rackmount enclosure they're pretty nice.http://www.antekinc.com/One advantage to solid-state diodes is that you can use very large filter caps without worrying about the tube arcing and sparking.Also, regarding the Heathkit, I would be willing to bet that the reason they used the 6X4 is because they had a lot of them in stock. Heathkit sold plenty of other kits back in the day, and a lot of the parts in that power supply are slightly odd choices and look suspiciously like they were originally specced for other equipment.Just my $.02

author: 001
author_rank: Super Contributor
timestamp: June 08, 2019, 04:59:59 pm
content: Quote from: H713 on June 07, 2019, 06:25:37 amnever heard of special " benchtop 500V tube PSU" parts

author: samofab
author_rank: Regular Contributor
timestamp: June 08, 2019, 07:23:31 pm
content: There are tubes that are specifically marketed for use in series regulator circuit. e.g. 8068

author: David Hess
author_rank: Super Contributor
timestamp: June 08, 2019, 08:21:20 pm
content: Quote from: samofab on June 08, 2019, 07:23:31 pmWhat makes them specifically suitable for series pass elements?I seem to recall that these tubes had unusually low anode resistance and would operate at low anode voltages but I do not remember how this was achieved.

author: samofab
author_rank: Regular Contributor
timestamp: June 08, 2019, 08:49:05 pm
content: Quote from: David Hess on June 08, 2019, 08:21:20 pmI don't really know and the datasheet is quite sparse (at least for me). I always assumed that intended use is just a marketing term . Perhaps this particular tube could be used in audio amplifier just as well (e.g. for electrostatic speakers).

author: Circlotron
author_rank: Super Contributor
timestamp: June 09, 2019, 01:16:46 am
content: Such a tube might have an unusually low voltage drop, just the ticket for series pass regulator duty, but the construction techniques used to get this low voltage drop might also make the grid volts vs anode current quite nonlinear and therefore not suitable as a normal grounded cathode amplifier. Similar to bipolar transistors - some are optimised for linearity, some are optimised for switching usage.

author: duak
author_rank: Super Contributor
timestamp: June 10, 2019, 12:33:57 am
content: Probably hard to find these days are television horizontal sweep tubes. These are tubes optimized for switching applications - in a way like power FETs and IGBTs are optimized for low RDS, high breakdown voltages and minimal drive and switching losses. Radio amateurs use them in power applications where non-linearity isn't such a big deal. There are a few articles on the tubes here:http://www.tetrode.co.uk/sweep.htmlI think one of them says that to get low plate resistance, the cathode is larger than one would expect. Scanning the vast wasteland of the 'net, I see that tube audio people that have tried them, especially the single ended Class A open loop folk, don't seem to care for them. I wonder if the thrash guitarists would?I would think that as long as the transfer function is monotonic, a good power supply could be designed using a sweep tube for the pass device.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 10, 2019, 03:14:31 am
content: Nonlinearity isn't such a big deal, it's mostly the 3/2 power law, typical of any tube. Frame grid and planar types tend to be worse actually, because of cathode space-charge physics.The relevant properties are: very high perveance (large cathode, small grid cross-section), close anode spacing (low Rp), and relatively high anode dissipation. This gives low mu, or relatively low gm, but as the cathode-grid voltage drop is usually used for the anode resistor of the error amp, it really only affects the headroom of the error amp.Which means if you are okay with a 250-500V supply, you probably won't need a negative supply, but if you need 100-500V say, you'll likely need a -50 to -100V supply, and then you might as well go slightly further and make it a -250V supply and go for 0-500V output range instead. (And, mind that now you're talking a >800V range on the error amp, and you may want to use a small power tube just to handle that; like, say, 6S4 but if it had higher mu?)Sweeps are the same way, but with the plate replaced by the screen of course (in terms of grid-anode / grid-screen spacing being similar), the grids aligned (to reduce screen current), and somewhat tighter grids to give higher Gm and mu_g2g1. Here the peak current is as important as the high perveance. Some other tweaks to beam tetrode structure and you get a useful saturation voltage under 100V.Tim

author: David Hess
author_rank: Super Contributor
timestamp: June 10, 2019, 03:43:02 am
content: Tektronix used tubes like the 6080 (sometimes with both triodes directly in parallel) and the 12B4 (sometimes lots in parallel).The 6080 was apparently intended for series regulators and the 12B4 was often used for them.

author: H713
author_rank: Regular Contributor
timestamp: June 10, 2019, 05:19:11 am
content: I would use tubes that are cheap and available long-term. Look at plate dissipation ratings. The 6L6GC might be a good choice- lots of good power supplies have been built around them, and there's a Russian equivalent that is very cheap.There are advantages of using tetrodes and pentodes instead of triodes for the pass elements, most notably what Pete Millett describes as a "simple, brain-damaged half-assed current limit" that can be implemented by limiting the screen voltage. The other big advantage is that big triodes are very costly in comparison. The 6AS7 was a very common pass tube back in the day, but both new production and NOS tubes are very expensive. Demand has brought down the price of new-production tubes used in guitar amps, and as such 6L6GCs in particular are pretty economical and have a 30W plate dissipation rating. BTW, for those unaware, there are multiple different tubes called the 6L6, and not all of them have the same ratings. Throw an original 6L6 into some circuits designed for the 6L6GC, 5881 or 7581 (all closely related to the original 6L6 in terms of characteristics) and there's a good chance of it red-plating or melting the screen grid (UL operation is very hard on the screen grid- the early tubes weren't designed to take that kind of abuse). Plate dissipation ratings are also lower on the old tubes.Quote from: 001 on June 08, 2019, 04:59:59 pmOf course there are no special parts for a bench 500V power supply, but there are parts that one would expect to use and parts that aren't. There are a lot of parts in that particular power supply that I probably would not have chosen if I were designing a bench power supply, but suspiciously turn up in other pieces of Heathkit gear. In other words, they were originally chosen and purchased for other kits.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 10, 2019, 05:52:11 am
content: Also 6BG6 (sweep version), 807 (coke bottle, RF), 1614 (metal, RF), etc.Mind that new "6L6s" are all over the place, at least in the cheaper brands. Everyone makes 6L6GCs, because of course they do, but they don't all handle 30W like a 6L6GC is supposed to. Derate generously (say 30-50% below rated), treat them more like 6L6GBs if that.Even then, the material quality is poor, so don't expect great lifetime.That's a nice advantage to industrial and PQ types: better materials, higher ratings, longer life. A $100 tube that lasts 10khr is a better deal than a $50 tube that lasts less than 5k -- assuming you have the budget to do so, and will be using the equipment frequently.Or conversely, if not, it may actually be a better deal to use the cheaper part, and then maybe keep spares handy, accepting that when (not if) the originals fail, you'll have the annoyance of changing them out, but you won't be SOL for a week awaiting delivery of new parts.One last thing. Mind that poorly constructed tubes are more likely to melt or arc over and fail shorted. Have some protection method in place (a crowbar?) to deal with this. It's most likely to happen at the lowest output voltages, where the load will be most vulnerable to a surge to full B+...Tim

author: H713
author_rank: Regular Contributor
timestamp: June 11, 2019, 04:30:46 am
content: Quote from: T3sl4co1l on June 10, 2019, 05:52:11 amJust my personal experience, but I've found that the new production 6L6GCs are pretty good. They've certainly gotten better over the last few years. Buy sets that have been burned in, you should be fine. I've pushed some of them pretty hard, and they take it. I'm running Tung Sol (new production) 6L6GC-STR tubes in one of my power amps, and they've been rock solid for over a year (figure five hours a day?), running at about 28W plate dissipation.Keep in mind what most of these are being used for- Guitar amps. Lots of them push tubesreallyhard, and in a lot of cases they are sitting just a few inches away from one or two twelve inch speakers that are producing earth-shattering SPLs. And remember- a lot of these amps are being blasted for quite a few hours at a time, and they aren't being babied. Your bench power supply will be sitting on a bench, away from speakers, and you probably won't be running them any harder.As a contrast, when I built my latest power amp using 1625 tubes (12V heater version of the 807, itself a version of the 6L6), I had two NOS RCA tubes and one NOS National Union tube that shorted after a total of about eight hours of usage running at about 19W plate dissipation.In addition, a lot of the alternative tubes that could be used have dwindling supplies that I would prefer to see used to keep existing equipment operating. Aside from my personal feelings on this subject, there is nothing more frustrating than having a piece of gear that uses an unobtainium part with a finite lifespan. Just ask owners of U47s and U48s how they feel about the supply of VF14Ms.Also, I would definitely suggest implementing something to minimize how much power is dissipated in the series pass elements. This could be as simple as a carefully chosen dropping resistors, or as elaborate as a variac controlled by a servo motor. I can attest that the later does work quite well. If you use the Antek toroid I suggested, you have a pair of HV windings. Switching transformer taps is a pretty easy way to handle this issue. That combined with a simple crowbar would go a long way to improving the safety of this power supply, though one must always remember that anything that can source 500V at this level of current can easily kill you.

author: 001
author_rank: Super Contributor
timestamp: August 17, 2019, 04:59:33 pm
content: Any news?

author: geggi1
author_rank: Frequent Contributor
timestamp: August 17, 2019, 06:33:18 pm
content: If you want at rough and simple 500DCV PSU without any features the resepy is simpel.- One transformer with secondary voltage of 350V.- Four diodes capable of at least 500V. Recomend 1N4007 or better.- Electrolytic capacitors with a rating of at least 500V (go for at least 600V capacitors) with plenty of capacitanceOptional- One variac to get ajustable voltage.- Toroide bifilar winded core for noise reduction.Rectify the 350VAC with a four diode rectifier bridge. Smooth the voltage with plenty of electrolytic capacitors. Add a bifilar wounded inductor to reduce the noise. The variac can be placed in front of the 350V transformer to have some voltage regulagtion.If avalable get a 230/380 transformer this will be avalable at companies like RS, but you will have to use a variac to ajust the voltage dowin to 500v

author: 001
author_rank: Super Contributor
timestamp: August 18, 2019, 04:34:57 pm
content: Quote from: geggi1 on August 17, 2019, 06:33:18 pmHoney. It is EE forum.Everybody can build simple Herz bridge hereThe story ofHVbenchtop tube PSU is always WERY tricky. So any benchtop PSU requires constant voltage and constant current modes. And big caps at lab PSU output is BAD idea

author: TERRA Operative
author_rank: Super Contributor
timestamp: August 18, 2019, 05:10:20 pm
content: I still got all the parts here for the unit as it is in the first post. I'll have to filter through the thread and see what mods I want to use for my final design...I haven't done any actual work on it yet, I keep getting distracted with the next shiny thing, but once my current project (A Fluke 332D restoration) is done, I'll get back onto this one for sure.

author: 001
author_rank: Super Contributor
timestamp: August 18, 2019, 05:50:43 pm
content: Quote from: TERRA Operative on August 18, 2019, 05:10:20 pmBest wishesLet`s us to know how