2040 problem

SX1010

New Member
my buddy has a cr2040, it powers up but no lights and no sound. my buddy says the fuses are blown. are the fuses on a 2040 easy to blow? is this a common problem on the 2040s? what would cause a fuse to blow?
 
I am literally working on a 2040 right now that had an issue with the 3A fuse that keeps blowing (the one that supplies the lamps). The source of the fault was a bad diode at D912 (one closest to the rectifier), which failed shorted. I replaced with a 1N4004 from the 'shack and now everything works...for the most part.
 
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I am literally working on a 2040 right now that had an issue with the 3A fuse that keeps blowing (the one that supplies the lamps). The source of the fault was a bad diode at D912 (one closest to the rectifier), which failed shorted. I replaced with a 1N4004 from the 'shack and now everything works...for the most part.

Thanks, do you know what would cause a fuse to blow for the output? do these units have speaker fuses?
 
My bad, I thought I read that just the fuse for the lamps blew. If an output transistor fails shorted it could cause a fuse to blow. Although...having both fuses blow together is a bit strange since they are on separate circuits. Make sure the fuses are the correct rating.
 
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output transistors are :

_2SB700( 2SB755)
_2SD736 /2SD845

Check if there is any in short circuit explaining burned fuse !
 
Is the fuse open or blackened on the glass? A blackened fuse is an indication of a dead short.
Are you saying the fuse in inline with the output/driver transistor circuit?
How do you know the fuse 'is for the output'?
 
My bad, I thought I read that just the fuse for the lamps blew. If an output transistor fails shorted it could cause a fuse to blow. Although...having both fuses blow together is a bit strange since they are on separate circuits. Make sure the fuses are the correct rating.

no worries, you helped me with the light problem...Thanks
 
Is the fuse open or blackened on the glass? A blackened fuse is an indication of a dead short.
Are you saying the fuse in inline with the output/driver transistor circuit?
How do you know the fuse 'is for the output'?

the Yamaha belongs to my buddy. he wants to sell it to me, but I want to know what's wrong with it (he has no idea). I do not know if the fuses ARE for output...it was a wild guess.
 
hello SX1010

here is what output transistors look like
 

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