Planning to build benchtop 500V tube PSU, help needed.

[001]

Great work 

What I’m using now is an electrophoresis power supply made by Bio-Rad 

Why? Can You post Biorad schematics?

[ArthurDent]

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. 

[001]

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.

Yea it`s really meaningless
And what about this analog beauty? I can`t google schematic for it

[gbaddeley]

EL34 PL509 PL519 or 807, in parallel to get enough current & power handling, possibly triode connected

[TERRA Operative]

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.

[basinstreetdesign]

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.

[TERRA Operative]

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.

[TimFox]

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.

[001]

hi

How are You? No posts for a long time 

[Wolfgang]

Hi,

sorry for no progress, but still searching the web for some realistic tube SPICE models.

Wolfgang

[TERRA Operative]

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. )

[KD4CCF]

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.

[schmitt trigger]

*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?

[duak]

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,

[schmitt trigger]

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.

[001]

For vintage stuff, it's often better to buy then recreate. 
Check out Heathkit IP-17 and IP-32  power supplies on ebay.

This is normal only for US customers.
Abroad, we can build a new one for the cost of delivery

[001]

Hi,

sorry for no progress, but still searching the web for some realistic tube SPICE models.

Wolfgang

How are You?

[Wolfgang]

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.

regards
  Wolfgang

[artag]

I've got a Kepco HB525 similar to  https://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 ?

 

[schmitt trigger]

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

[artag]

 

[chris_leyson]

There is always this monster http://www.pmillett.com/HV_bench_supply.htm with 807's !!

[romhunter]

There is always this monster http://www.pmillett.com/HV_bench_supply.htm with 807's !!

I'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.

[coromonadalix]

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

[H713]

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 go really 1970s 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