Hi,
In the middle of covid lockdown boredom and despair I bought a Fluke 720a in" working state" from the usual auction site.
When on my bench I opened it to check if it would contain most of what is is supposed to contain, and superficially checked
fuctionality for major problems, fearing the successive big regret for spending a lot for some useless paperweight.
To my suprise (the final price was low, but delivery + customs added to total final cost too much) the unit seem to be mostly
fuctional, at least no big problems.
The test was simple and a bit naive: I connected a voltage source to the 1.1 input and my 6-digits multimeter to the output and
regulated the voltage source to have a nice round 10V reading to the output with the divider set to 1.000000
Then started moving the dials decade per decade to see if the reading was coherent with the ratio set.
To my awe the reading was stable to last digit plus or minus 1, had to compensate for some drift of voltage source and
multimiter a pair of times but the final divided reading was astonishingly stable... wow
That was going almost too well untill G dial, the least significan digit one, that was tricky to asses but reasonable
until I selected "3" as last digit... there the output became totally messy. x.xxxxx4 was ok x.xxxxx2 also but x.xxxxx3 was jumping all around.
My suspect went immediately to S7A resistors, so opened the lid and here is the last divider... notice anything strange?
Here is it:
Who knows what happened to this soldering joint... I don't want to think that Fluke would let the unit out of production with a missing
soldering joint but the only other explaination is that someone messed with the internals. Who knows.
Anyway, can I just solder it back with regular SnPb solder?