[Milsurplus] Vibrator replacements

[Michael Kane]

With regard to recent discussion of solid state vibrator substitutes, I
would like to add my own experience over the years. The two transistor self
excited version works well for smaller loads. I have used these in vintage
farm radios etc, from the 1930s to early 1950s with

no needed mods to existing circuit,  for synchronous versions just add
diodes to rectify.

Higher loads the transistors have to be well heatsinked, or added in
parallel with balancing resistors. Some years ago I switched to 4047 or
like driving FETs. Modern FETs have incredibly low on resistance with
minimal heat generated, and little heatsinking required. This makes things
a lot easier to stuff into the original vibrator cans.



At the moment I am working on a revised design using one of the Chinese PWM
SG3525

modules which have adjustable frequency down to 100hz and variable PWM
settings, as well as onboard FETs capable of sinking up to 1amp, and an
onboard 5v reg.  All this for the price of around AU$ 2.50 posted, less in
quantity.  Just look for SG3525- LM358 PWM on the site we all love and
hate. There are a few versions, mine has two pots, and is the size of
larger postage stamp.

Price varies wildly so look around.



I intend using one of these to drive higher power external FETs. Another
advantage of the variable PWM is dead-time added to the switching waveform
as per the original mechanical devices. Total all up cost around AU$ 6 to
8.00 per vibrator. I will post my results.


I need two of these for restoration of an Australian  WW2  WS122 Army
transceiver. The original octal based vibrators are in soldered up metal
cans, and have all the problems one expects after 60+ years inactivity.
Desoldering the cans destroys the original labeling.



     Michael VK4ZKT
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