The 940uF 40V capacitor just dates to before we had
the modern preferred
values system. If it is just a filter capacitor, a 1000uF 50V should work
I don't think that;s the whole story, for several reasons :
The old preferrd values, at least in the UK, were a cobling series (1, 2,
4, 8, 16, 32, 64 uF) and decades multiples therefor. (for example, 640uF
was a common Philips one). The HP values have no particualr pattern
There are hP boards with (offiical, as documented in the service manual)
odd-vlaue capactiors which are close in value, like 5600uF and 6000uF
I have a schematic here for the HP9826/9836, from the 1980s. The colour
monitor PSU (for the 9836C)( has a 900uF smoothing caapcitor on the input
to the 12 regulator (C22), not 1000uF. The main smoothing capacitor in
the computer is 21000uF, not 22000uF. This machine was designed and sold
long after the adoption of 'modern' preferred values.
-tony