bad garbled up video on sega master system I

When I got the master system in, it had no video whatsoever (unsure about sound). So I replaced all capacitors, checked the voltage regulator, and resoldered all the solder joints because many of them was cracked due to age. I now get video but it's all garbled up, and don't know why. I originally tested it using RF but bought a composite cable for it, hoping it was just the RF output, but it does the same thing. Any solutions? Thanks.