How can I boost the +2A's RGB signal?

[Sparky]

So my +2A works on my small CRT TV/monitor but wont work on my older Samsung CRT which has both a SCART and composite input. My friend's C-64 works perfectly with the composite cable he has. I think the +2A's signal isn't strong enough?
Any solution to this?

[Guesser]

I suspect it's this: https://spectrumforeveryone.com/technic ... compliant/

[Sparky]

Thanks! Now I have to get my soldering iron back up, I thought it would be an easier solution, but this seems good enough for now.