Am 13.08.2013 21:38, schrieb Rob Klein:
Op 13-8-2013 20:16, Joseph Gray schreef:
I came across a couple of old Fluke differential voltmeters that
need some
work. I thought it would be best to use low thermal EMF solder on
these.
I think it would be best *not* to.
As far as I know, Fluke never used any low thermal EMF solder on any
of its equipment, even
the very top-of-the-range stuff. I certainly never seen it mentioned
in any service manual
for e.g. the 720, 845, 750, 752.
Rob.
I have encountered only one model of equipment that needed low thermal EMF
solder; a Holt model 323 AC Voltage standard. The special Cd/Pb solder was
needed for the low level circuitry around the thermocouples. I discovered
this in my first encounter with these units. I used regular 63/37 solder
for a repair and found wild excursions (tens of millivolts) in the output.
A bit of reading in the manual disclosed the necessity of the special solder
in the unit. Luckily, there was a small hank of the Cd/Pb solder inside the
unit, which fixed the problem.
As for HP and Fluke equipment, I have never heard of the need for special
solder, even in the most tightly specified standards. I don't know if there
would be any adverse effects if the low thermal EMF solder were to be used
in those instruments, but unless it's specifically documented to be
necessary, I would be reluctant to use it, especially since it's so
unobtanium.
Cheers,
Dave M
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