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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Autopsy on the body of a voltage regulator
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/ |
#2
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Autopsy on the body of a voltage regulator
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 |
#3
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Autopsy on the body of a voltage regulator
"n cook" wrote in message ... tomh wrote in message ... 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 |
#4
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Autopsy on the body of a voltage regulator
Dave D wrote in message
... "n cook" wrote in message ... tomh wrote in message ... 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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