tomh wrote in message
...
hmmm, the 317 data sheet from national doesn't list an absolute V max
input but does list a input output max differential V of 40V so for a
15V output you should be good to a 55V input. Still if it were me I'd
try to knock down the input DC somehow. If you go thru the numbers for
heat/thermal transfer you're probably right at the limit. That maybe the
reason you've "welded" the insulator and "cooked" off the lettering. Try
to get a sense of the temperature of the device, I suspect you will find
it's a bit on the toasty side.

tomh

n cook wrote:

Well sort of as still functioned and no downstream damge, but replaced
of
course anyway.
USA kit 120V, powered up in UK at 240 V this LM317T set for 15V out
survived 40 or 50V instead of 25V at its input.
Clamped to heat sink with a thick Ali bar pulled against the body so
sandwiched between 2 bits of ali. The grey PTFE/Teflon or whatever it is
insulator was "welded" to the metal of the V Reg and all lettering
disappeared from the other face. Anyone else seen this before, no
explosive
eruptions from the body at all.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/




I just cracked it open and it looks or rather looked perfectly healthy