Micromoog Blowing Fuses. Please Help!

[chuckfalcon]

Hi everyone! I went on a craigslist hunt for a guitar and ended up finding a dusty old keyboard tucked away in a corner on the way. This keyboard was a Micromoog, which I got as is and untested. Cosmetically it was in super condition so it was worth a gamble. I bring it home, fire it up, and get nothing. Pop it open, blown fuses. I get fresh fuses, pop 'em in, turn it on, I get power for about one second and then both fuses blow.

All of the wiring and solder joints look to be original and it doesn't look to have seen any rough use. Does anyone have any ideas of how to get started fixing this thing? Replacing caps in the power sections? Testing the transistors on the power supply board? What are your ideas. Any and all help is very much appreciated.

Thanks,
Chuck

[thealien666]

Hi Chuck.

Congrats on getting a Micromoog (I think).

Fuses that keep blowing in the PSU section means that there are components downstream that consume much more power than they should (shorted out). It could be anything from capacitors (especially Tantalum type that tend to short out over time), to some op amp (1458 and CA3080 have a tendency to get bad over time also), or any other components. The best thing would be to have a good tech have a look at it.

Good luck.

Alain.

[chuckfalcon]

Hi Chuck.

Congrats on getting a Micromoog (I think).

Fuses that keep blowing in the PSU section means that there are components downstream that consume much more power than they should (shorted out). It could be anything from capacitors (especially Tantalum type that tend to short out over time), to some op amp (1458 and CA3080 have a tendency to get bad over time also), or any other components. The best thing would be to have a good tech have a look at it.

Good luck.

Alain.

Thanks, Alain! I ended up diving into it this afternoon, and came across a bad diode on the power supply board. I believe it was CR104. I don't have any on hand to replace it and check but I have some on order, as well as some new filter caps for the power supply section. I will keep you up to date with how it goes.

[miczac]

Hi, did you get it to work? m.