More tests today...
Can't find any power transistor / regulator faulty anywhere in the +24/+30 volt circuit. Even on the boards that use these voltages. There's very few card/circuit using the +30, only Transport Control (A). If I understand the schematics correctly, it's used for solenoids and motors. +24 seems to be for external record sign only... I cannot understand WHAT could have made that fuse to blown, except a faulty card power input regulator, but they are all ok, and provide correct voltage to the specific card. Could it be a problem with some logic control that activates ALL solenoids/motors at the same time, that drains so much current that the fuse blown?
The problem happened when turning ON the machine. Last time I used it, it worked perfectly.
One more interesting thing: removing and re-inserting the card with the power still ON confirm that the motors are working. So is the capstan. Something's funny though: the capstan is ON or OFF independently from the tape sensor. (random state when I turn on the machine). That random state seems to be ordered by the MASTER CPU board cause if I remove it then re-insert it, the state changes randomly... Hope I'm clear... But, there's nothing on the master cpu board that is related to the +24/+30 rail, so I don't get why something faulty on that card could cause a blown fuse.
I'm about to drop this sh** and sell the machine in parts! There's a lot of parts in very good condition on this machine, I would definitely get more $ out of parts than out the complete recorder in its current un-working state...
So before I take my hammer, any other ideas????