Wanted: Circuit for HV PSU

[eddie_ce]

Mods - If this is better in the wanted section please transfer.

I am looking to build a simple HV PSU - Input ca. 300V Output ca. 150-250 V variable. Current ca. 70mA, max. 100mA.

Can anyone point me in the direction of a suitable circuit using EL34 or EL84 or similar as pass regulator.

Many thanks

[AC/HL]

I'm sure members will have plenty of suggestions, but this simple search returns a good selection of design ideas: https://www.google.co.uk/search?q=va...w=1280&bih=873

[GrimJosef]

You can learn a lot from reading this piece by Steve (now Stephie) Bench http://diyaudioprojects.com/mirror/m...ench/reg1.html

Cheers,

GJ

[M0FYA Andy]

Copy one of the Solartron circuits in this manual.
Andy

[G6Tanuki]

Rather than using audio-valves (whose characters are somewhat less than ideal) for the series-paqss circuit, remember that there were valves specifically designed for this duty.

The 6080 being probably the most well-known example.

http://www.r-type.org/exhib/aaa0725.htm

Sample circuit [by RCA] using one is shown here: http://www.gammaelectronics.xyz/audi...ulated-PS.html

[GrimJosef]

Yes. If you were thinking of using an EL84 then an EL86 - similar in lots of ways but purpose-designed as a pass valve - would be a better alternative. And unlike the '84s the '86s are dirt cheap.

Cheers,

GJ

[Skywave]

I realise you did state that you are looking for a valved PSU. But would a transistor type be of any interest?

Al.

[eddie_ce]

Guys, thanks for your replies, plenty to study over the weekend.

Al, in this day of cheap FETs more than suitable for the job, it would seem the sensible option, however nostalgia rules and I would like to see filaments glowing

I basically want to build a small general power supply suitable to power my small valve projects during the development/construction phase.

[Herald1360]

If you don't need high stability HT, what about a variac feeding a simple rectifier-filter supply?

[joebog1]

Although it doesnt use audio bottles, it does work exceptionally well, and just about fits what you were after.

Joe

[eddie_ce]

Thanks for that Joe, looks more or less just the job

[k_yller]

on cheap valves

[GrimJosef]

Since the heater supplies for the two valves share a common 6.3V transformer winding it might be worth biasing that at some voltage between the HT output and ground. Otherwise the limit on Vhk is likely to be breached either for the EF80 (150V) or the PL504 (250V). Also if the supply's output really does go up to 370V then the EF80's Vak limit (300V) will be breached, although not by much.

Cheers,

GJ

[k_yller]

Circuit is a kind of idea (however its work) of course biasing EF80 is necessary

[G6Tanuki]

Small heater transformers are cheap: in the past when I've used valves like the 6BW6 807 or EL34 as "series gate" screen-grid AM modulators - where the cathode can often be running at 350V above ground (which is well beyond their rated H-C insulation spec) - I've just used a separate heater transformer and strapped the cathode to one of the heater-pins so everybody's happy.

A classic big juicy ex-Admiralty HT transformer often had a couple of specially-well-insulated 0-5-6.3V-at-a-couple-of-amps windings designed to feed directly-heated rectifiers; these can be used to supply 'floating' heater power if you're using silicon diodes as the main HT rectification.

In the past there were also special 'high voltage insulated' heater-transformers available, designed for CRT duty: RS/RadioSpares had a range...

[Skywave]

Originally Posted by eddie_ce

Al, in this day of cheap FETs more than suitable for the job, it would seem the sensible option, however nostalgia rules and I would like to see filaments glowing

O.K. - understood. The only reason I mentioned a transistor type is simply because I designed and built my own a couple of years ago, so there is a proven design available and you can talk to the designer / builder - if necessary. It's O/P is 100 → 300 v.d.c. @ 100 mA regulated plus 6.3 v.a.c. @ 3-amp. Figures are approx., since the transformer determines the max. out (V & I) subject to the series pass device (a power FET) having adequate rating.

Al.

[Philips210]

Hi Al.

I'd be most interested in seeing your variable regulated HV power supply circuit if you don't mind sharing it with us.

Regards
Symon.

[joebog1]

In designing a new valve tester, I collected at least two dozen variable power supply designs. I spent a couple of months going through every electronic construction magazine on Americanradiohistory.com. None of them is as elegantly cheap and functional as the little Electronics Australia design though. I have downloaded most of those designs if you want more. I have the origional magazine for Electronics Australia .

Joe

[Skywave]

Symon - O.K., fine! I'm flattered that someone wants to see it!

Below is a technical description of how it works; cct. diag.; a few design remarks; photos of the front and the insides. The cct. diag. drawing is a bit rough since it is a copy of a copy (it was originally intended for my eyes only, afterall ) and I had to reduce the resolution to fit the requirements of this forum. But I think it is readable.

The next post has a photo. of the control board.

Al.

[Skywave]

Photo. of control board.

"Huh? Transistors to tag strip?" I have been asked before. Reason: ease of prospective corrective maintenance: hopefully,that need will never arise!

Al.