Hi teatime,
[...] but the CPX400S/SP MAIN BOARD(PN:35555-5430-3C) is different.
The form factor is different but it is more or less the same schematic than for the CPX400D.
It seems that the inrush current limitation (R1/RL1) has been removed for the CPX400S.
Before fiddling/making mesurements on the main board (PFC), I strongly encourage you to use/buy some
electrical safety gloves, because of the high voltage/significant power present in this area.
As far as I can remember, if everything's fine, you shoud find about 390 VDC at the output.
Also check for any sparks damage : if the PFC controller goes bersek, the output voltage might raise up to 10 kV

an arcing is inevitable.
I send the email to factory for the service manual, but the factory didnot reply me till today.
Same situation here : I asked for buying the CPX400S SM about 1 year ago but got no response (1).
And
Keith on hackaday seems to have made the same request quite recently.
(1) Don't know why AIM-TTI currently keeps silent. Ten years ago, they sold me several SM for a realy fair price and I was able to successfully repair the defective equipement.