[volt-nuts] Fluke 725 and 726

[pa4tim at gmail.com]

Can someone help me with 2 Fluke service manuals or schematics fot the 725 and 726 proces calibrators ?


I have here for repair a Fluke 725 that has a fried ADC. It has been to a Fluke dealer for repair and you do not want to know how bad that job is done. (missing pads and traces , cold solderjoints, , a relais facing the wrong way, the -5V from the 4053 tied to gnd, a damaged resistor etc. )  I'm 100% sure the ADC is dead and 95%  that is the only problem left but have not ordered a replacement yet because I hope for a manual so I can check the rest for hidden supprises caused by the dealer.


The 726 from the same customer that came in this week only has a TC problem.  I traced the TC output to an opamp and analog switch. In TC mV mode he measures it correct but in K mode ( I only haver K TC's ) or any other TC's except for N, he shows the letter of the TC so that part works.  But no value in derees.

As far as I can gues the ADC measures the voltage, and the software does the conversion. But in that case it is weird it measures and displays the voltage correct. So I think there must be some switching before the ADC but I can not find it. I get stuck at the opamp.

and ADC because they are hidden behind the display making it hard to measure. I use a lab powersupply and an extender cable to the keypad but the display uses those bloody zebrastrips.


A lot of the repairs I do are older, rather exotic gear with missing schematics/service doc so I'm used to finding my own wayvbut I'm not that masochistic, so I prefer to use documentation.


Fred

Schneider electronics repair bv

www.schneiderelectronicsrepair.nl

www.pa4tim.nl