Junkbox Voltage Doubler - Vero

[Toney]

  I have been looking at ways to power submini tubes and this is a small spin off from that.
You can make a voltage doubler from standard components in case you need more voltage and you don't have a MAX1044 or similar handy. Its small enough to fit sideways in a 1590B and its not too picky about parts, you probably already have them in your junkbox...


                             

 BC547/BC557 are listed on the Vero but it will work with any common types such as 2n3904/2n3906.

 It's an astable multi-vibrator, like those little LED flashers you find in hobby electronics kits but running at 50KHz driving an NPN/PNP "engine". You can add as many stages as you like. I have just built a multi tapable one here:
http://www.diystompboxes.com/smfforum/index.php?topic=74088.220 Which is the same thing, just more stages tacked on.
You can use 2n3904 or any common trannies for the oscillator. For the NPN/PNP output stage 2n3904/2n3906 can do 200mA. I think it would be possible to use a beefier set such as 2n4401/2n4403 which can do 600mA or even BD139/BD140 if more power was needed. Not fussy about caps either, obviously they need to handle the voltage though. I used all 33uF because that's what I had on hand. The circuit draws ~10mA at idle. For diodes I used 1n4001's to test it which are probably a crap choice as they are lossy and slow but hey, they work.  I think UF or schokky types would be best but it will work with all common types so long a they can do the current.  So its not quite a doubler. Well, its a doubler minus the diode losses.  I got ~16.5v with a 9v battery and ~ 24v with a 12.8v supply which could be improved with better diodes.
I haven't tried powering anything with it yet, just built and tested the circuit. So hopefully no horrible noises coming through but the ocillator runs above audio frequencies so that bit should be OK! May require power filtering for whatever it supplies.
Original pages with schems here:
http://www.sm0vpo.com/power/vconv_01.htm




The first part, the oscillator shares a lot with the Boss flip/flop, just free running as opposed to latching.

[Toney]

 Same deal as above but with two - four stages %^&*roft Walton style.
Up to 44 v out with 12v in. Caps only need to be rated 16v except for C1 which need to be 25v.

                   

           

That's supposed to read C o c k r o f t Walton.

[freakazoidas]

Hello,
i am currently building this - http://www.sabrotone.com/?p=233 and i was wondering could i just throw Junkbox Voltage Doubler in the same box, connect 9v input to Junkbox, 18v junkbox output to fx 18v input and ground, to the same ground as the fx? (i am sorry if this question sounds stupid, i am a noob)

[Toney]

Absolutely - thats kinda what its for!
I would suggest getting the Junkbox Doubler up and working separately first. Probably a good idea to add some filtering to the front end of any effect that comes after it. The oscillator is out of audible range but its good practice.
A 100uF and 100nF cap from power to ground first after the power input should cover it.

[Pyr0]

Hi Rod, I built this but made it a voltage trebler, I'm looking for approx 25v so it should work.
I get the correct voltages under no load, but as soon as I put any load on it the voltage drops from 25v down to around 12.4v, even just using a 10k resistor as the load causes the voltage to drop, and with a 10k load it is only drawing 1.44mA

I also noticed a mistake in the vero layout, the negative connection from C2 should go to the emitter junctions of Q1 & Q2, in your layout it looks like it's going to the base of Q1 & Q2.

Any idea on the voltage drop  ?

[Toney]

 Hi Alan,
Good catch on the electro, I'll update as soon as I get a chance.
I did this some time ago and built it as larger version, which worked great for me up to 93v without issue. I was interested in higher voltage power supplies for a week or two then moved on once I had met my needs.
Here: http://s2.photobucket.com/albums/y16/stm88/?action=view&current=CWaltoncompact-1.png
As far as load goes, what are you supplying it with? I tested at 9 and 12v with a regulated supply rated at 1amp, and marked the voltages on the larger version I linked. So please test it with a regulated wall wart type supply if you aren't already. I built this on the breadboard and probably tested with the same. Which layout did you use ? Running it at 12v as a doubler or at 9v as a trebler?
The only other things I can think of off the top of my head are diode recovery speed and caps, assuming that your build is error free. But hey, seeing as you picked up an error on the vero I am guessing it probably is Lol. So you could try a larger cap in place of the 22uF and faster diodes if you have them.
I'll dig up my build later today or possibly tomorrow morning and test it under load for you.
EDIT:
Veros updated.

[Pyr0]

I was running it from a 9v battery that was in need of a recharge  .  It also works fine now when I use a 9v or 12v wallwart. Thanks.

[azrael]

Very cool, much better output current than a MAX1044.