marc, there are a number of responses to your problem
- You need to use the original TV remote to access service mode. Other remotes will probably not work.
- The VGA-SCART cable I made for you auto-switches into AV mode constantly by sending 12v to pin 8, so that will may thwart your attempts to enter TV service mode while using that cable.
- You would temporarily disconnect the 12v power supply, if you feel confident. You could do this simply by temporarily removing the pin from the molex plug (12v is yellow). The cable will still work, but you'll need to select AV mode manually.
- Otherwise, try service mode with the TV on normally, without the SCART cable attached.
Otherwise, you are stuck unless you can find/borrow a real remote! You could try taking the TV to a TV repair shop, where they might have the remote.