Bob,
No I didn't do an amp-off mod.
I was always going to at a later stage and probably the least
invasive version
the one where you only solder to a leg
of the CCD).
I found that my SPC900 had high noise in the blue channel
at mid to high gain and if I couldn't eliminate that then I
assumed the amp-off mod might make it worse.
(A few forums state that the amp-off mod lowers the sensitivity
and adds electronic noise to the image because of the wiring
hanging off the boards due to mods).
In use I minimise the blue noise by having long exp frames below
15 secs, gamma at 50% (DSOs) and gain at about 50% or lower.
HTH,
Steve