How To Fix A Yamaha BK7i Organ Amp? - & AC or DC ?

Hello all.  I am very new.  Today. First post.  Just stumbled across this forum 

Looks good to me.

I am trying to fix our old Yahaha BK7i organ which just gives out loud white noise and blows a fuse.

I'm not trained.  Just an enthusiastic DIY person I guess.

Friend helping me said to measure current at F3 - replace the fuse (that's the one that blows) with my DMM on the 20A scale and see what it draws.

Fine.  Then I suddenly thought.  AC or DC?

And I've been measuring voltages all over TR's 4 - 7 on DC scale. Is that okay or should they be AC?

Lots of info on my imgur posts.  Tried to put a pic of the circuit here but it wanted a link so I've linked to it.

And here's a link to the whole 'album' of pics about the organ:  https://imgur.com/a/K2exqQ0

Excuse me ignorance.  Please enlighten me.

abrogard said:

  Then I suddenly thought.  AC or DC?

Click to expand...

Fuses don't care about AC/DC; they are sexless. 

And I've been measuring voltages all over TR's 4 - 7 on DC scale. Is that okay or should they be AC?

Click to expand...

This is DC here in the absence of signal.

What happens if you disconnect connector US1? You should have no signal, just a little hiss, and maybe slight hum, the normal noise of an amp being alive.

abrogard said:

Friend helping me said to measure current at F3 - replace the fuse (that's the one that blows) with my DMM on the 20A scale and see what it draws.
Fine.  Then I suddenly thought.  AC or DC?

Click to expand...

The current thru F3 is AC. However, if F3 blows, most probably the amplifier or speaker connected to it are faulty.