I have an old Yamaha electronic organ. And it just broke. Main amplifier Fuse 3 blows all the time. I wonder if anyone could look at the circuit and give me their opinion of what might be causing it?
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Thank you. I will see if I can do it. I've added some more pictures to the imgur post so's you can see where the board is. At the bottom left hand on a big metal chassis. I think I will have to take it out to get at the things on it.The diagram shows two 2200 uF/63 volt electrolytic capacitors adjacent to the fuse and transformer. If you desolder and remove the two capacitors, then carefully apply power momentarily and see if F3 blows or not. Aging electrolytic capacitors fail occasionally. Note the + and - polarity marks on each capacitor and their installed orientation.
I haven't done anything more yet. Too busy. Will get onto it as soon as I can. I did manage to put the manual up where you can get at it:Do you have the page on what is connected to US2-S? F3 also goes to whatever circuits that might be connected via that connector.
I'll have a go at that when I get down to working on it. It's a good idea?Add an incandescent mains lamp (40W or so) in series with the mains. That will limit the current and may help you find the problem.
Or, you could put a 24V tail light lamp in place of the secondary fuse. It will allow the amp to power up to some extent, but limit smoke. You will not be able to run the amp at any power levels like that, but it will be enough for you to test things without running through a lot of fuses.
by Duane Benson
by Duane Benson