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

[TERRA Operative]

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!

[001]

look my old tread
it is not possible
simply buy one

[TERRA Operative]

What do you mean it can't be done? Did you see the attachment?

[001]

What do you mean it can't be done? Did you see the attachment?

Yea
this is common regulator circuit of sixties

What do you mean it can't be done?

but it is not lab PSU since no any current control
Many peoples here told me keep HV away

[Moshly]

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/

[TERRA Operative]

but it is not lab PSU since no any current control
Many peoples here told me keep HV away

That's ok, as it is just for powering tube amplifiers during testing and repair etc. No need for super accurate voltages etc.

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/

Holy 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....

[Cyberdragon]

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).

[TERRA Operative]

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?

[001]

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).

Wrong way
since internal PSU impedance is not small, parasitic feedback in the circuit under test is sufficient
few pass tubes eliminate problem

[tautech]

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?

A 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.

[Wolfgang]

Hi,

have you seen that there are books full of PSU designs for tube audio, like this one:

Valve Amplifiers, by Morgan Jones

or have a look at this thread of EEVBlog:

https://www.eevblog.com/forum/projects/overhauling-high-voltage-vacuum-tube-(valve)-power-supply/msg389145/#msg389145

play safe, have fun.
  Wolfgang

[David Hess]

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.

[TERRA Operative]

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)?

[001]

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)?

it is wery difficult at XXI century
Do You Really NEED 500V output?

[Wolfgang]

You need two 450V caps in series with equalizing resistors. No big deal.

[Emo]

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 working

Eric

[Wolfgang]

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 fun
  Wolfgang

[001]

- Make the whole regulator floating.

Can You illustrate it with tube circuit?

[TERRA Operative]

You need two 450V caps in series with equalizing resistors. No big deal.

Ah yep, I completely missed that one. Easy enough to do and caps are cheap.

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 working

Eric

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 fun
  Wolfgang

I 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 200V

I'm also interested in how I would make the reguator floating too.

[001]

6aq5 so crappy
try TV tube
it is rugged and cheap

[Wolfgang]

Hi,

I will post a floating design in a few days, sorry for the delay.

[Dave]

What do you mean it can't be done? Did you see the attachment?

Yea
this is common regulator circuit of sixties

What do you mean it can't be done?

but it is not lab PSU since no any current control
Many peoples here told me keep HV away

Yes, they told you to 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.

[TERRA Operative]

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.

Either that, or the electricians callouses offer me enough insulation resistance to keep me relatively safe. 

[TERRA Operative]

6aq5 so crappy
try TV tube
it is rugged and cheap

Do you have any suggestions? I'm not as well versed in tube substitution as I am with silicon...

[001]

6aq5 so crappy
try TV tube
it is rugged and cheap

Do you have any suggestions? I'm not as well versed in tube substitution as I am with silicon...

Try this http://tdsl.duncanamps.com/show.php?des=6KG6

U still not  say how much mA do You need