I have a Macintosh Plus, which as soon as I turn it on shows the floppy icon and then resets itself immediately afterwards. Note that it does so as soon as it needs to power up the floppy drive. For example, if I unplug the floppy drive connector, the Macintosh Plus will not reset. The floppy drive works correctly because it has been tested on another macintosh plus, and the logic board also works correctly, because this is also tested on another plus. The only thing I have done on the analog board is to go over the solders (especially in the junction connectors), and change the two capacitors C1 and C2. I did not recap the other capacitors. Note that even if I turn it on without floppy and try to vary the screen size horizontally, as soon as I enlarge it a little more, it resets.
I have replaced all the capacitors of the video card, I have also gone over ALL the contact tracks of all the components of the video card but without openable results. I am sure that the defect lies in the video card because (having two macintosh plus) I tried to put this card in the working one and it gives me the same problem. Unfortunately I do not have an oscilloscope available and I was wondering: it is possible to connect only the video card, without connecting it to the logic card, and from the first check the output voltages from the cable that goes to the logic card, with a normal tester and possibly check voltage drop by manipulating the trimmer of the screen adjustment? Or risk something?