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Forum index » Electronix » Repair
Autopsy on the body of a voltage regulator
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n cook
electronics forum Guru Wannabe


Joined: 11 Jan 2006
Posts: 153

PostPosted: Mon Jul 10, 2006 10:28 am    Post subject: Re: Autopsy on the body of a voltage regulator Reply with quote

Dave D <dave-d@dave-d.com> wrote in message
news:6K2dnc0DAbVchi_ZnZ2dnUVZ8qKdnZ2d@pipex.net...
Quote:

"n cook" <diverse8@gazeta.pl> wrote in message
news:e8nrat$noj$1@inews.gazeta.pl...
tomh <nospam@ll.mit.edu> wrote in message
news:EWvrg.1865$O5.1307@llslave.llan.ll.mit.edu...

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



You must have a lot of free time on your hands! :-)

Dave



So I can take it on good authority that the Lincoln Lab does no research.
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Dave D
electronics forum Guru


Joined: 08 Sep 2005
Posts: 486

PostPosted: Mon Jul 10, 2006 9:19 am    Post subject: Re: Autopsy on the body of a voltage regulator Reply with quote

"n cook" <diverse8@gazeta.pl> wrote in message
news:e8nrat$noj$1@inews.gazeta.pl...
Quote:
tomh <nospam@ll.mit.edu> wrote in message
news:EWvrg.1865$O5.1307@llslave.llan.ll.mit.edu...

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



You must have a lot of free time on your hands! :-)

Dave
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n cook
electronics forum Guru Wannabe


Joined: 11 Jan 2006
Posts: 153

PostPosted: Sat Jul 08, 2006 8:16 am    Post subject: Re: Autopsy on the body of a voltage regulator Reply with quote

tomh <nospam@ll.mit.edu> wrote in message
news:EWvrg.1865$O5.1307@llslave.llan.ll.mit.edu...
Quote:
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
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Tom Hotaling
electronics forum beginner


Joined: 07 Jun 2006
Posts: 9

PostPosted: Fri Jul 07, 2006 4:23 pm    Post subject: Re: Autopsy on the body of a voltage regulator Reply with quote

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:

Quote:
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/


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n cook
electronics forum Guru Wannabe


Joined: 11 Jan 2006
Posts: 153

PostPosted: Fri Jul 07, 2006 2:50 pm    Post subject: Autopsy on the body of a voltage regulator Reply with quote

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/
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