I want to thank you PKTKS for your kind answer, I've already tried to download those GITHUB links -but- there's a problem 4 me:
Several of those files, I cant' be downloaded, and, more of all, I don't know how to compile the firmware.
I'm not a programming nerd, so I have difficulties trying to compile these things.
Also you finally suggest to be careful with the programming fuses...
Since those are ALOT fuses inside the microcontroller, I really don't know which is which and their correct configuration I need to set them to be able to program the new microcontroller I bought AND to be able to reprogram it anytime in the future. (In case it will break again)
I'm a simple user of the TC1 tester, not making them in any production... I simply want to repair this valuable tester... don't want to do anything else with it...
Believe me, all this is a mess as it is, from my pov.
I'm not a master in all this, unfortunately.
similarly, that little PCB to replace the U4... I don' have a PC equipped & power enough to handle also kikad to read those files (I already have a mess of applications on my PC, that I use for a lot of other jobs, and don't have enough time to learn new programs.
The electrical scheme of that little PCB would be already enough for me to replicate it.
Consider that I'm 62!
So if you or someone else could link me:
- the already compiled firmware (any version, .hex or .bin) compatible with the U4 hardware PCB modification;
- could tell me how to set the fuses to be able to use the thing, and can read/reprogram it eventually anytime AFTER;
- and finally could give me a screenshot of the schematic to replace U4, I would be TOTALLY GLAD.
That's all I need.
Thanks for the attention.
Mario