I want to build a regulated adjustable 0-300 volt DC supply. It is for testing different tube headphone amplifier configurations. So current is not a large need but something that would have 1 amp available would be nice.
Mostly I want it as clean as possible so it will make a good B+ supply.
Does such an animal exist? Any recommendations?
Jeff
Mostly I want it as clean as possible so it will make a good B+ supply.
Does such an animal exist? Any recommendations?
Jeff
Well well, so 1 amp isn't large? At 300V, it's still 300W... different people, different points of view (and if it has to be clean++, that means purely linear).
Note that I have such an animal in my files, problem it's not in electronic form, and it was basically for my own use, thus not very understandable by somebody else (even I, after 5 or 10 years would probably have difficulty putting the pieces together).
I can tell you for sure that a good HV lab supply is not something exactly easy.
Ill try to see if there are useful bits I can post.
In the meantime, you can have a look at a project I have posted, it is a mix of a switching pre-reg with a linear post reg; it achieves 0-400V and a 1 amp capability, but not at the same time: total power is limited to ~60W IIRC.
It does work well, and if it is well done, it combines the effectiveness of a switching supply (on the cheap) and the cleanliness of a linear supply.
Edit:
After all, I have something in electronic format, but this one is a real monster, a 0-700V 1A one, but it gives you an idea of what to expect...
NOT SOMETHING FOR BEGINNERS!!!
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Why not copying an old Heath/Zenith supply.It's "only" 100...125mA ,for headphone amps (and more) largely sufficient.
Here you find the service manual, schematics print and how to use it.
http://www.jogis-roehrenbude.de/Roehren-Geschichtliches/Roehren-Netzteile/SP2717A.pdf
Mona
Here you find the service manual, schematics print and how to use it.
http://www.jogis-roehrenbude.de/Roehren-Geschichtliches/Roehren-Netzteile/SP2717A.pdf
Mona
Jeff:
Some other older supplies to check:
Eico 1030
BK Precision 1602
Heathkit IP-17
If you really want to build it yourself, it's a good challenge. However, IMO, it will be a lot cheaper to buy one of those power supplies (ebay) and refurbish with new caps, etc. . vs buying new parts. Of course you may have a big supply of old parts there....😀
The Eico and BK are selling for ~ $100 + shipping, the Heathkit for ~ $200. (Heathkits sell at a premium, for some reason...)
BTW, most of the supplies also have bias (C-) supply as well as B+ and heater (6.3v) supply.
Replace R1+R7 by a pot.
R4 sets current limit and can be switched of course.
I even have a PCB for it if interested.
Jan
R4 sets current limit and can be switched of course.
I even have a PCB for it if interested.
Jan
What voltage will this output and what does the input need to be for 200vdc out? If it meets my needs i am interested in a board.
Jeff
Do you absolutely need adjustability from 0 to 300V? If you can get by with less voltage adjust range, such as say from 150V to 300V, you may want to consider something like this approach. (see post 38 on that thread for the updated schematic). This is essentially the author's take on Michael Maida's approach, based on his 1980 brief while at National Semiconductor.
Probably about 215V DC unregulated input for an adjust range that would give you up to 200V DC regulated output. Might also need to tweak or redo the voltage adjust method to give you more voltage swing. Basically you might need to move the voltage adjust pot to the R9 position, and replace R4, R5, and R6 with a single resistor of size 120 to 180 ohms. I can't say more specifically right now, I'd have to experiment.
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Here is another circuit you could modify. Or if you could live with a 120v reg. you could use this. I know both of these have a minimun output of 1.25v but if you just had to have 0v output a cheap fix might be just 2 diodes in line with the output to drop the voltage about 1.3v .
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Usually there's a capacitor to ground on the adjust terminal, with a discharge diode between the adjust and output.
It will output anything that doesn't blow the caps and the pass transistor. The '740 can handle up to 400V.
Input should be at least 10V or so above the Vout.
I do not have boards in hand (they're all gone) but I can provide the Gerbers to have boards fabricated.
You also need a separate (floating) heater winding to supply this regulator's control circuit (shown on the schematic).
Performance is very, very good. Very quiet, very stable.
Jan
Your PS must have to be able to supply 300W+loss=approximately 350W-400W.
You have to deal with heat problem if use solid state. At the low output voltage levels, the power loss that will turn into heat will be near to 300w which is too much so needs a huge heatsink.
If you will use it only for testing different amplifiers,
You can use an isolated variac with a power 300W, a simple bridge rectifier and a CLC filter with an inductance, say, 1 H and 6x680Uf 450V.
Simple, reliable and handy.
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