[tony brady]

Hi Colin

I have done a 7603 & 7633 but not a 7623A ( so far). you can make some checks without removing the module - is there any voltage on the HV test point? ( -1475V, accessible through a hole in the cover) if it's low remove the black wire going into the potted eht module as when it fails it can load it down. there are also several high value resistors you can check from the top once the supply is discharged.

you can also check the T03 switcher in situ. I would check that the supplies are present before removing the module

if you want to completely remove the module take good pictures and be very careful with the white/ red & white/ brown single wires marked A & B. do not get these reversed on re-assembly. you need to remove the Z axis board mounted on top of the module so take pictures here as well. remove the eht plug to the tube at the side of the module.

remove the connector to the tube base and the other 2 ( or 3?) noting the orientation as the small arrows are not easy to see denoting pin 1.

there are 3 screws holding the module to the chassis, 2 are easy to see but the other one you must remove the plug ins and bottom panel - use a long screw driver with blu tak on the end

it's quite a lot of work so go carefully

good luck!
cheers
Tony