I had some doubts about TR1 and TR2, so I checked their voltages, they looked OK (the 0.2v difference I was talking about earlier was not there anymore, I don't know why).
I decided anyway to replace them. TR1 is managing luma, I replaced it first (yes, I should have started with the chroma one (TR2), but I did not sleep very well last night ...
). Of course, no change. Then I replaced TR2, and that was the culprit : now the colors are very good !Just for information, my motherboard is an issue 4S, TR1 and TR2 were referenced "C945 Y-4D6". I replaced them with "ZTX313".
Thanks a million to all of you for your help, especially to Mark.
Now I still have 2 other Spectrum to put back to life :
https://www.sinclairzxworld.com/viewtop ... &start=100
https://www.sinclairzxworld.com/viewtop ... 519#p37519
Thanks again !