Short answer, Doug... I have no idea. I do know the AC is square wave, so it will need massive filtering. My practical side is saying if I want battery bower to just build a standalone SS battery powered inverter, but I'm fascinated by this weird little mechanical marvel. Something magical about touching 12vdc and seeing all that AC on the other side. Inspires dreams of running my guitar rig powered by hamsters.
Brad Linzy Not really a square wave, the vibrator contacts drove a transformer which has inductance and there was a capacitor in parallel to protect the contacts, so the current took a little time to rise and a little time to decay. So probably more triangular?
Wasn't it rectified ? IIRC, it was rectified with either selenium or later germanium diodes in bridge configuration, filtered. Indeed, noise was present at the reception, and the vibrator if mounted rigid on a metal case or plate...was awful. However it was the backbone of inverters before power solid state came .
Very interesting, Brad. I remember hearing the buzz of EM Inverters like this in old car tube radios from the 1950's. I believe the output of this device is a square wave (rather than a sine wave), which might create some filtering problems in an audio amplifier circuit. Here is an interesting and basic article on Inverters in general that covers the old EM devices: electronics.howstuffworks.com/gadgets/automotive/dc-ac-power-inverter2.htm I guess the modern version uses a solid-state oscillator to achieve the AC output. Thanks for posting this and sharing it with us.
What sort of EM interference will be created by this infernal device? I see that a capacitor is used across the points, much like in automotive distributors, to eliminate arcing. 50's car radios using this seemed to work pretty well, without a lot of interference, but that was RF. It should be an interesting project.
Thanx for sharing, as it brings back some memories! :) :) Sorry to say this, but you can pretty much forget about it, as it´s all mechanical, if you load this thing it varies a lot in terms of working frequency and stability. You can try it, but i´ve done it as well some 20 years ago, to built up the same but with no luck. If you really want to build a tube based amp powered by batteries, you may go for battery tubes, or check out the car inverters you can buy today. Usually they have a 12Volts input and an ac outlet where you can plug in pretty much everything if it´s not exceeded the rating. That´s the easy way. If you want it the hard way, here it is: Build up a DC/DC boost converter. You can use a 555 and a PowerMosFet for this. Let it oscillate at about 50kHz somewhere. Hook up a coil to it (of course you have to wind it up all by yourself) and regulate the coil´s output voltage through a feedback circuit hooked up to the control pin of the 555. You have just created a simple PWM controlled boost converter. But if you overload it it´ll just blow up, as it is not short circuit proove. And you have to tweak it until it works on your load (= the Amp) And it will draw a lot of current. If you want to have an Amp with let say 12W out of EL84/6V6 in PP or similar, it´ll need some 50Watts overall input power. To power it from 12V DC you need around 6Amps continously.....What battery you want to carry..?....;)
This idea is shelved. Just my limited experience with this thing on the floor showed me how unreliable it would be. Half the time it wouldn't get going. Thanks for watching the video and replying though! I do think this was an ingenious solution back in the day, but it's just not a practical one today when we have so many better alternatives available.
Never the less, you can do just a little "PlayMachine" around it, just to show everyone that, at least, a tiny, Itty-bitty thing with let say two 6BM8 or 6GW8 is possible, as they draw only 20mA@150Volts in PushPull expecting 1-3 Watts output. And their heaters wired in series would perfect fit to a 12Volts battery. As you already have one of these old choppers lying around. So have some fun with it, but do not try to power a full featured Amp with it....;)
I'm not trying to be negative here, but a randomly chosen transformer and buffer capacitor is a recipe for problems. It is not the vibrator's fault. The buffer capacitor must be selected using an oscilloscope. With correct operating conditions there is no sparking at the contacts - ever. Likewise the transformer must have a minimum amount of primary inductance and some ordinary mains transformers used in reverse are not suitable. There is a very good book written by Mallory on the subject, and the fact it is 129 pages long should indicate there's a lot more to it. The apparent simplicity of a vibrator inverter is always a trap for the unwary. In reference to the vibrator not working at first, this is common when a vibrator has not been used for many years and is the result of an insulating film forming on the contacts. It can easily be burned off with high voltage within a few seconds. As I use a lot of vibrator powered equipment, some vintage, some I've designed and built in the modern day, I can say the technology is extremely reliable when used correctly. If you're interested in vibrator power supplies, I'd recommend this site members.iinet.net.au/~cool386/
