No signal from PC on TV

[snorkerz]

Hi, Can anyone offer any suggestions...

PC with Hercules 3D prophet 4500 TV-Out Card (SVGA & S-Video)
|
S-Video & Audio to Composite convertor
|
10m composite cable
|
Composite input on Wharfedale LCD32 TV
OR
Composite/Scart adaptor into TV

I have set the card up on the PC and it is clearly set to dual screen (TV & Monitor)

My sons X-Box was formerly working on the composite input on TV, replacing the X-Box cables with the TV cables = no image. So TV composite IN is obviously working.

Connecting via available scart = nothing!
Connecting X-Box via scart - okay

I have used the 10m composite cable on the x-box/TV link - it's fine.

A search for

Audio / Video Adapter Cable / 7 Pin S-video / 3.5mm Stereo Audio To S-Video / Composite Video / 2x RCA Audio Cable

on play.com will show the adaptor being used at the PC end.

Problem is obviously, either the above adaptor or the card itself, how do I check these?

TIA