[volt-nuts] Fluke 731B replacement

[Randy Evans]

I am planning on building an equivalent Fluke 731B transfer Standard using a VRE310 10V Precision reference and LTC5400 Quad resistor as a precision 10:1 divider, plus ancillary circuits.  However, before starting the detailed design I modeled the Fluke 731B circuit in LTSpice.  The 1V, 1.018V and 1.019V outputs are fine but the 0 to 999uV delta E adjustment circuit for the delta V, 1.018 + delta E and 1.019 + delta E outputs does not work per the circuit modeled from the schematic.  I have double and triple checked my LTSpice schematic per the Fluke 731B schematic but I can't see any difference.  Maybe I am just too close to the forest to see the trees.  
 
Note: The Fluke 731B schematic from the manula I have does not show the value of the delta E adjustment pot but the parts list shows a value of 5K ohms.
 
Does anyone have any ideas?  I can forward the LTSpice schematic I am using to anyone that might be interested, just send me your e-mail address.
 
Thanks,
 
Randy Evans