Electronics > Repair

Fluke 5700a repair

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veedub565:
I've been having a bit of a poke around the linearity control area

U2 and U38 both replaced with new parts
Q4,5,6,7 all tested working
VR7 tested working

One slight difference is Z2 which says 14k and 11k on the schematic, but I measure it as 14k and 14k (even with U38 removed). it seems rather too precise to be a fault, possibly an error in the schematic

Ugur:
Z2
14 Kohms from 1 to 2 pin
11 Kohms from 2 to 3 pin

Legs 2 and 3 are connected to legs 2 and 6 of U38.

Maybe there is a revision as you said!

veedub565:
So a small update on this

Having got my 5700a to pass all it's diagnostics tests. I was lucky enough to be able to take it into the UKAS lab at work and perform an artifact cal. I left it switched on for 24hrs to warm up and stabilise. I had access to all the correct (calibrated) 10v, 10k, 1ohm standards.

The 10v part went through with no issues, and a small change of around 7ppm (which doesn't seem to account for the large PPM this instrument is out by)
The 10k part also went through, but with a rather larger change of 137ppm

The 1ohm part failed though with the following error message - "Couldn't Ext Cal 1 Ohm (Ext Meas) (2582)". This appeared while it was performing the 1.9ohm part of the cal.

So it that would confirm there is still a problem with this instrument. The artifact cal was aborted and no changes made to stored cal values.


Question is what does this fail mean, and which board to start investigating. I guess first would be to take a look at the Ohms Cal board.

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