Mac Plus analog board - Scoping recap needs

[erichelgeson]

Hi all,

I'm scoping what I need to fix my Mac Plus analog board. The Mac Plus does work, it chimes and putting a floppy in will boot, but the screen is blank. The "smack the left side hard" did work and flicker the screen, though it of course is not a solution!

I believe the Flyback Transformer is shot - I've attached a photo where you can see the leads are burnt almost and some corrosion on the top - though I'm not quite sure what it should look like.
 

The board looks otherwise ok - not a lot of bulging or corrosion outside of the flyback.

So my question is - really how to proceed and what else I should look at? Replace the flyback transformer? Is there a way to test the transformer? Do more debugging? Replace some other more common components first? 

 

[cheesestraws]

I believe if "thump the side" worked, the usual culprit is dodgy solder on the J1 (?) connector (my Dead Mac Scrolls is all the way downstairs).  I'd try reflowing the solder on connectors/resoldering before I tried replacing any components with that set of symptoms, honestly.

 

[erichelgeson]

Thanks for the pointer @cheesestraws - after taking a closer look at the back the J4 connector had bad solder joints - along with a few other places that I didn't see on the first pass. I reflowed them and it works like a charm. The Dead Mac Scrolls is quite handy!