Hello,
I'm doing a portable Master System (which, with a little of luck, I will post here when it's over ) and just made the A/V connection on my Optimus Pocket Color TFT LCD TV. The sound is functioning normally, but the video is full of strange characters on the screen. You can see some "scroll" of the game when it is running.
I saw on http://portablesofdoom.org/page.php?page=sms that you can use some capacitors to amplify the signal, but since on a normal TV the A/V mod is working normally and also is the sound on the pocket TV, I don't think it's the case.
Does anyone know what might be happening?
Thank you very much.

Strange characters are a problem with the console most likely, probably either a voltage issue or the cart and slot needs cleaned.

Thank you, but the console is still running with the normal power adapter and the TV with the batteries (however, I already put the white led mod and desolder the TV tunner).
And the game is the "built in memory" version of Sonic, so it is running without any cartridge.

Try it on a TV first.

As I said, on a normal TV the A/V mod is working normally. Also was the pocket TV channel signals before the removal of the TV tunner.

Pictures needed to continue troubleshooting.

I'm trying very hard, but all I get with my f* cam are photos and videos showing the TV working with a black screen.
Enlightenment is not enough for her to capture the image, but I'll keep trying or get another camera with someone.

I see you're using some sort of translator, so I'm thinking that 'characters' is not the word you meant. It seems likely that you just meant a scrambled screen, which is likely caused by the values of the capacitors not being exact. LCD screens require higher precision for what they receive in input than a normal TV. You need to replace the fixed value capacitors with variable capacitors where the middle is where the desired capacitance rating, so roughly twice the value indicated for the highest value of the variable capacitor. Adjust the capacitors to the indicated value in the diagram using a multimeter to measure, install them, then make small manual adjustments afterward to get the image stabilized.

Success!
I used similar schematics of the nes (those on the book) and it worked. Now I just need to figure out how to convert the signal from Pal-M to NTSC, because the console is brazilian and the TV is american, so the screen turns only black and white.