Yamaha C-4 pre-amp help

[avionic]

I found one of the 500mA 250V fuses with a broken wire.

That could be your problem. That provides both of the amplifier's front ends with +/- 80 vdc.

 

[avionic]

Ok, the M-4 looks like it’s never been opened. Very dusty. The RCA connections look ok to me right now. I’ll dig more. I found one of the 500mA 250V fuses with a broken wire.

Replace both of them with new 500ma pieces.

 

[Nashou66]

Ok, the M-4 looks like it’s never been opened. Very dusty. The RCA connections look ok to me right now. I’ll dig more. I found one of the 500mA 250V fuses with a broken wire.

Do you have a Dim Bulb Tester to use for power up?

Was the fuse wire broken or was it burnt?

If broken you might get away with no DBT for power up.

Good luck !