Michael Black wrote:
On Fri, 4 Nov 2011, JIMMIE wrote:

I came by what appears to be a power supply module from some old
military gear. It uses a synchronous vibrator unless my analysis of
the circuit it way off. My plan is to build a circuit to replace the
vibrator with a couple of power FETs driven by a 555 osc and a bridge
rectfier to handle rectification of the output. I was wondering if
there were any circuit designs around before I started to reinvent
the wheel. Also what freqency do they use. Seems like I heard 100Hz
at one time but I dont trust my memory on something I learned 40
years ago. Any help would be much appreciate.

The earliest replacements would have been a couple of power
transistors on a heatsink, with a few resistors and capacitors,
relying on the existing transformer for feedback (and frequency
control).
Of course a lot of early power inverters were about the same, save
that they weren't built around a vibrator supply.

Look in forty year old ARRL Handbooks, I'm certain the 1971 edition
(the first I ever saw) has a simple inverter that is on that level.

I'm sure some built fancier ones, but I'm sure many got by with
something pretty simple. SOme small companies that deal in antique
radios sell virbrator replacements.

Michael VE2BVW


Yes, there are several schematics on the web for solid state vibrator
replacements, but most are too simplistic and are prone to failure due to
unsuppressed transients destroying the semiconductors.
There is one that appears to be a good design at
http://antiqueradios.com/gallery/v/temp/VIBRA2.jpg.html. The component
values are all indicated on the schematic. The circuit can be built into a
salvaged vibrator can. Be sure to provide some method of heatsinking for
the transistors. The only drawback that I can see with this circuit is the
lack of "dead time", that is, a short time interval at the switching point
to keep both transistors from conducting at the same time. A more involved
design might be able to eliminate that problem.
This circuit is the one I would build if I were in need of a vibrator
replacement.

--
David
dgminala at mediacombb dot net