[volt-nuts] Fluke 720a self calibration repair

David Garrido d.garrido at me.com
Thu Sep 24 18:31:54 EDT 2015


After having spent the last couple of hours getting to know the switching, schematic, circuit, and layout I had a chance to lift the leg of R1006.  Measured spot on as did R1005 and R1007.  I was able to measure those resistors in the tank as well.  Having done all of this I was thinking about the VERY same thought to find the center as I did have to turn all of the pots in the “A” decade in the same CW direction to bring them into spec.  If I remember correctly as I was checking the R1005 (20 turn pot), I recall it bringing the resistance out of R1005 down, as I was turning the pot CW and that was lowering, so opposite.  I am going to try this and if all the rest falls into place after the adjustments, I will call it a success.

BTW……….so far after initial inspection and testing, the 335D, 845AR, and the 721a all seem like they just needed cleaning and adjustment.  This is the only one left from that 7105a Calibrator and I have a 750a on the way to finish it all out.  The 5200a is all clean and adjusted and I am still working on a small issue in the 5205a.  Other than that, I just need a 540b and a rented 3458a to calibrate all of the calibrators.


Thank you so much for allowing the bandwidth.



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