First, are you certain that you have modified the lead in the manner you think, are all the ground connections on the Video (Yellow?) and Audio-Left (White?) and Audio-Right (Red?) connected to the ground on the 4 pole 3.5mm connection?
BTW The connections are normally referred to from the tip as: Tip-Ring1-Ring2-Sleeve which is what I will use here.
Your pin-out does indicate the right connections though, which is a good start:
- Tip - Right Audio
- Ring 1 - Left Audio
- Ring 2 - Ground
- Sleeve - Video
You will also need to make sure you have the right Composite-Video-Blanking-Signal setting in your config.txt file, the values for sdtv_mode are:
- 0 = Normal NTSC (3.57954545 MHz colour sub-carrier)
- 1 = Japanese version of NTSC without a pedestal
- 2 = Normal PAL (4.43361875 MHz colour sub-carrier)
- 3 = Brazilian version of PAL (PAL-M) – 525 lines / 60 fields per second rather than 625 lines / 50 fields per second, (3.575611 MHz colour sub-carrier)
In the UK I need to use 2.
If you are connecting the TV via a Phono-to-SCART adapter or the TV has the RCA Phono inputs itself you do need to manually switch to the appropriate input manually, the TV will not switch to it automatically as it would with a full SCART interconnection like what you might have with a DVD or VCR.
You may also want to check that there is no setting that is forcing the RPi into using the HDMI connection - have a look through the relevant sections of the ELinux wiki documentation (from which I retrieved the above sdtv_mode details): RPiconfig.
