[Milsurplus] [MMRCG] Parts Box Inverter

B. Smith smithab11 at comcast.net
Tue Apr 2 15:09:37 EDT 2024


No one seems to like the  imported power supplies that operate at a much 
higher frequency. But if you determine the frequency then you can build 
a proper filter et.
They are very efficient sometimes around 85-90 percent and can fit into 
a small enclosure.
An example of proper noise reduction can be found here:
http://k4che.com/Tempvideo/Zenith/Zenith%20k4che.mp4
K4CHE

On 4/2/2024 1:39 PM, Robert Nickels wrote:
> On 4/2/2024 10:11 AM, Ray Fantini wrote:
>> The transformer is a 36 volt and although it is not happy about being 
>> driven by a square wave it works and provided a good range of output. 
>> Thru trial and error found this one to be best. Transformers work 
>> both ways so you can use the primary as the secondary and they don’t 
>> know the difference. The trick is to not exceed the insulation 
>> value.  Cheap Radio Shack transformers tended to get hot or buzz.
>
> Good job Ray!
>
> The transformer is the secret to these things, and many just won't 
> work efficiently (hot) or put enough back EMF into the FETs that they 
> get hot or fail from overvoltage.    Mallory built bazillions of 
> mechanical vibrators and vibrapacks and literally wrote the book on 
> how to design power supplies using them - you can find it online: 
> http://www.tubebooks.org/books/mallory_vibe.pdf
>
> There's a whole chapter on transformer design (and more) - but of 
> course you can't buy one nowadays. However you can scrounge them - or 
> experiment with what you have and maybe find one that has the desired 
> magnetic characteristics.   Vibrators typically ran around 100 - 120 
> Hz.    I haven't tried a 400 Hz transformer yet but it might be a good 
> way to go, and a bit smaler and lighter as well.
>
> 73, Bob W9RAN
>
>
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