exxos's Atari, Amiga & retro forum

Hi all, I require your expertise because my STF is killing me. I have an MB C070789-c1, and I installed the dual TOS with a decoder. It was working almost fine, so I decided to apply all the fixes suggested on the EXXOS forum. Everything was fine until the last one to solve the 10K nightmare.
Unfortunately, other than replacing all the SIL, I also removed the TOS sockets to lower the Dual Tos board. I wish I were clever enough to do one mod, test and then do the second, but I didn't. Now I find myself with a white screen when I turn the STF on. I checked the following:

On PSU exit, I have 5V and 12V
On the FDD power cable, I have 5V and 12V
On the video connector, I have: on pins 4 and 13 = 5v fluctuating between 4V and 5V.
on pins 9 and 13 = 15,79 Khz.
on pins 12 e 13 = 60hz that is weird because the TOS is UK.
No soldering seems cold, and on the bad-looking one, I checked the connection between the pin and the track.
I also used the EXXOS test cartridge, but still no video. And using a serial cable, on my terminal, only a weird character appears (see image).
I have attached a few images of the MB, the Test cartridge configuration and the terminal output.
I am not proud of my soldering skills, but my health conditions don't let me have very steady hands.
Only your skills can help me to try to solve the mystery.
Thank you all in advance for the help.

A white screen generally indicates your ROMs aren't working.

Since you have a TOS 1.04-2.06 decoder be sure that you are not trying to use TOS 1.04 with the TOS 2.06 decode enabled as that won't work.

If it still isn't working than I'd suggest you pull out the just the DualTOS board and try with your original ROMs.

It could be that the 2.06 decoder isn't installed correctly and has bad contacts so you may need to consider that too.

Hi, thanks for the tips. I'll give it a try.
Quick question: does the diagnostic cartridge replace the TOS when you insert it, or does it work with it?