On Sep 26, 8:04 pm, clare at snyder.on.ca wrote:
On 26 Sep 2007 21:14:28 GMT, (DoN. Nichols)
wrote:





According to lew hartswick :

[ ... ]

Anything else you would like to know about vibrator power supplies?

Well ... something else to *add*. The typical automotive
vibrator ran somewhere near 60 Hz (since there were lots of 60Hz
transformers around), but I had (and may still have somewhere) a special
vibrator and matching transformer which had the reed weighted to lower
the frequency to 20 Hz, and it was used to generate the ring signal for
small telephone exchanges -- from before the Sub-Cycle passive devices
to do the same thing by dividing the 60 Hz power line frequency by
three. (I never have been able to find out exactly how they did that,
but I have two sealed units of that type -- different load capacities.

Don -
I didn't understand much of the telephone industry electronics
either :-). Possibly some weird trick with using ferromagnetics in
what is in fact a non-passive way. Were the converters by any chance
unusually heavy and dense, indicating a lot of iron? Oh, never mind,
everything done in the phone industry in those days was unusually
heavy and dense! Modern phones just feel so cheesy!

I remember the vibrators being something like 255 hz. High frequency
is easier to filter, and works just fine on lower frequency
transformers.

Indeed, most Mallory automotive/truck radio vibrators that I've seen
are rated for 230 Hz nominal. I think that was about the limit for the
mechanical construction used. Electrolytics were not as reliable or as
plentiful in those days as they are now, so anything that let them get
by with smaller filter capacitors was worthwhile.

There are higher frequency tuning-fork vibrators used for DC
instrument choppers... this was the 1960 timeframe. I think HP's (and
others) opto-choppers took over by the 70's.

Tim.