I've added resistors in series with R1008 and R1044 to bring the resistance for those parts of the A divider to a value that it would calibrate OK (two of the resistor sets in the oil bath very low in value). I also had to remove five turns (about 1.3 Ohms) from R1051 as the combined value of R313 and R314 was too high to allow me to calibrate S2. I also replaced R1041 as it was worn out (almost impossible to get a null).
I've successfully calibrated the C decade as per the maintenance part of the manual. Sadly the beast isn't giving me a nice linear voltage sequence when using just the A decade. Input voltage 100.001,4V fed to 0/1.0 Input terminals All Decades set to zero except Decade A. Decade A Output V 0.1 9.999,88 0.2 19.967,8 0.3 29.936,7 0.4 39.903,8 0.5 49.874,7 0.6 59.855,6 0.7 69.852,4 0.8 79.871,3 0.9 89.919,6 See also attached graph. Any suggestions on where to look for trouble will be most welcome ... All sections of the A decade attenuator now measure about 9.999,2 ohms. It was suggested on eevblog that the next decade (or a subsequent one) was loading it, but with all the other decades set to 0 I don't quite "get" how. Thanks Dave
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