[Milsurplus] Easy DC to DC inverter

[Ken Gordon]

Well, I'm with YOU, Ray. Thanks for this.

Ken W7EKB

On 25 Jun 2024 at 15:11, Ray Fantini via Milsurplus wrote:

> 
>     Some ideas work so well and are so simple is hard to wrap your
>     head around them. Last couple years have been playing around with
>     solid state inverters for powering tube equipment in the field.
>     Recently Craig, N3TPM turned me on to this simple circuit, have
>     also seen this several places on the internet so decided it was
>     time to try it for myself. Near as I can figure it´s a
>     multivibrator or at least that´s how I drew it. I have put
>     together a couple of these on the bench and have to say that due
>     to its low parts count and simplicity find it hard to beat. Uses a
>     regular transformer and, in this case, using a center taped
>     twenty-five-volt two-amp transformer and it develops 120 volts on
>     the secondary all day long. The transistors are nothing special,
>     just 2N3055 or the like from the junk box. Unloaded current drain
>     is only around six hundred mills and with Rx being 680 ohms the
>     running frequency is around sixty cycles, increasing Rx raises the
>     frequency and lowering Rx decreases the frequency. When Rx is 250
>     ohms was running around fifty cycles and at 1.2 K was just above
>     seventy cycles. Have not tried it yet but would like to see what
>     this will do to substitute a mechanical vibrator, going to assume
>     that it will work but have not gotten that far yet myself.  
>     Additional comments are commentary: Do not read if easily
>     offended! Ok, so I know that there is a plethora of cheap Chinees
>     crap out there that you can buy for nothing all day long but screw
>     that stuff. Why buy when you can build? The advantage of this
>     circuit is its low frequency so there are no big noise issues, it
>     uses cheap junk parts and can be understood and repaired by anyone
>     with minimal understanding of electronics, just try repairing or
>     replacing something on one of those small micro inverters. Basic
>     assumption: We do this because this is what we want to do, not
>     because it´s easy, or cheap. If we were only interested in
>     getting on the air and racking up contacts there are way better
>     things then playing around with this stuff. Don´t know, maybe
>     some feel they may not be up to the task of understanding or
>     building their own but what better way to learn? Big advantage to
>     working with a lot of this old military stuff or any vintage
>     hardware is its bigger, easy to work on and easy to understand
>     where as modern equipment that´s microprocessor driven or using
>     LSI devices and surface mount technology are way more difficult to
>     deal with. Least that´s how I see it, or perhaps I am just a
>     victim of my own prejudices along with my own personal history and
>     preferences, maybe in twenty years people will look back and
>     regard these as the "Golden Days" when cheap Chinee´s junk
>     freed us from having to use soldering guns? As you can tell it´s
>     a slow day at work, and I have time to sit around and write up
>     such dribble.   Ray F/KA3EKH