[Milsurplus] Design for a cheap 400Hz power supply

[Gregory W. Moore]

Rich, this is a usual ploy from avionics companies. I guess they have to fund
their "Malpractice" insurance, like every other organization even remotely
connected with aviation.
Having spent my career as an aerospace avionics engineer, I can tell you that
there are 3 grades of any electronics, or any other component.  I will use the
good old RTV rubber for example. First, of course is "consumer", comes packaged
in an attractive tube, is covered with "warning" labels and legal disclaimers,
and has no expiration date.
Second is "industrial", a rather plain tube, no warnings or disclaimers, and
less expensive than the "consumer, again, no expiration date.

Third is "mil-spec" and "avionics grade". This costs about 1000% more than the
other two per unit. Comes with voluminous specification sheets and inspection
records, and most definitely has an expiration date, usually of only about 2
months, after which it must be discarded (ALL the RTV caulking and sealing in my
home has been done with this grade ROTFL).

The interesting thing is, of course, that all three grades come out of the same
vat, at the same time, and only the tube is labeled differently.

I will check with a few of my contacts (I'm retired disabled now), and see if I
can't scare up a manual copy for you, no charge. It's my way of striking back at
the idocy of the "great aerospace/avionics ripoff".

73 de WA3IVX (Greg Moore)

Richard Brunner wrote:

> Yes!  I bought, inexpensively, a solid-state 24-32 vdc to 115 volt 400 cycle
> 2500 va inverter, intending to convert it to 800 cycles.   Well, Avionic
> Instruments Inc. wants $250 for the instruction book and schematic, so
> conversion is academic.  It's complicated, with 40 power transistors and a
> driver board with no visible adjustments.  However, it works fine; I loaded
> it to 900 Watts, and the output voltage didn't move a hair.  This is fine
> for the PRC-47, (400 cycle) but not good for the TBW. (800 cycle)  The
> output transformer sings a bit at 800 cycles, and when the cooling fan comes
> on it sounds like a shop vacuum, but is less noisy than the 800-1 rotary
> inverter.
>
> Richard Brunner, AA1P
>
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