On Thu, 14 Jul 2016 15:40:04 -0000 (UTC), Cursitor Doom
wrote:

I've got a linear PSU that uses a LM317 (TO-220 case) to drop 37V down to
12V for a small 555 timer board that's set up as a pulse generator (at
about 0.1Hz).

The data sheet at:
http://www.ti.com/lit/ds/symlink/lm317.pdf
says that 37V is the maximum output voltage with an input-output
voltage difference of 40V absolute max. With 37v in and 12v out,
you're within spec, but seems to me too close for comfort. Maybe you
blew up the LM317? Try another LM317 and watch your input voltage
carefully. Or maybe add a big dropping resistor between your 37v
supply and the LM317 input.



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Jeff Liebermann
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