Progress at last!
Firstly, many thanks for all of your help and contributions
I was just getting myself in a mess and going in ever-decreasing circles before - stopping to explain the problems, and seeing the feedback from yourselves, was incredibly useful.
I switched a scart lead from the NTL 'video out' socket to the TV, and for the first time, saw an RGB output from the STB
I undid all the cables, tuned the TV to the very poor rooftop aerial RF feed, and started again with the scarts. Bottom line is, one of the scart leads that I had convinced myself I had tested was bad.
I now have the following -
STB (TV) -- TV
STB (Video) --> DVD-R --> TV
VCR -- TV
All of the above via 21-pin scart
I also have the RF out from the STB feeding into an RF amplifier, and the RF back to the VCR, DVD-R and an upstairs TV.
I have one remaining issue though - please advise if it is appropriate to continue this thread, or start a new one...
As stated above, the 'video' scart out from the STB goes to my Panasonic DVD-R (DMRE55EBS). It comes into the DVD-R via Ext2. When I setup the Ext2 via the setup menu, if I choose RGB as the signal input, I get sound but no picture (just black screen). If I change it to composite video, as the expected incoming signal type, I get picture and sound. The same is true if I feed the 'TV' out from the STB into the Ext2 of the DVD-R. The TV indicates that I am feeding an RGB signal from both STB outputs, if I do a direct connect to the TV.
This indicates to me that the NTL box is either not outputting 'standard' RGB (?) or that there is some incompatability between my particular model of STB and DVD-R.
Anyone else experienced this, or have any comments? Is there an easy fix, or do I have to approach NTL for a different model STB?
Anyway, I am much happier than I was before ... I just need to find a way of feeding RGB instead of component video to my Panny
