KORG Mono/Poly fuse - what kind of capacitor is that?

KORG Mono/Poly fuse - what kind of capacitor is that?

Postby Pepe » Sun Jan 07, 2018 6:28 am

My KORG Mono/Poly synthesizer recently stopped working in the middle of a jam session. After engaging the power switch the LEDs do only light up for a split second but nothing else happens. I had to do a full recap anyway and in the last two nights I have replaced 97% of the electrolytic capacitors (apart from those few with values that I didn't have at home, like 0.44µF and 0.68µF). Some of the caps had already funny looking legs. But I know that the problem with the power is a different and very obvious one that I have yet to repair. Here's the component that has burst:

Image

Is that also some kind of electrolytic capacitor that can be powered with 250V? Is it also prone to aging and drying out, or does it only explode if something is really wrong with the power? It is a synthesizer from 1981 and it gets quite warm inside, but that's normal with this model. It does always only work properly after ten minutes of heating up, but that is the normal behaviour of the Mono/Poly.

I'd like to know what that part is so I can replace it with the identical type. Or is it a case of "Whoa, Pepe, be careful - there's something severely bad going on if THIS part has exploded"? I hope it's just a component that died of its long age.

Thanks a lot for your help! :thumbs:
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Re: KORG Mono/Poly fuse - what kind of capacitor is that?

Postby Laurie » Sun Jan 07, 2018 6:59 am

Looks like old-age to me. No need to worry. It isn't electrolytic - it is a poly of some sort. Can you take a pic of the other text on the side of it?
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Re: KORG Mono/Poly fuse - what kind of capacitor is that?

Postby Pepe » Sun Jan 07, 2018 7:28 am

Great, I'm relieved! Here are detail pics.

Image

Image
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Re: KORG Mono/Poly fuse - what kind of capacitor is that?

Postby Pepe » Sun Jan 07, 2018 10:38 am

Okay, I have found a substitute model for this capacitor. It's an Electromagnetic Interference suppression film capacitor and in an audio forum I read that these are nowadays a common problem in old devices, because of the plasticisers used in the old models that tend to make the plastic perish over time. They are also called jumping cracker. :mrgreen:
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Re: KORG Mono/Poly fuse - what kind of capacitor is that?

Postby Laurie » Sun Jan 07, 2018 1:15 pm

Yep. Just replace it with an equivalent. 250VAC or 600VDC.
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Re: KORG Mono/Poly fuse - what kind of capacitor is that?

Postby Pepe » Thu Jan 11, 2018 6:01 am

I just replaced it. The problem remains. :( I have to explore further what keeps the synth from powering correctly.
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Re: KORG Mono/Poly fuse - what kind of capacitor is that?

Postby fuzzbuzzfuzz » Fri Jan 12, 2018 9:25 pm

Just after the power enters is there a voltage regulator component? A sort of square black component poking up with silver legs? I can't recall exactly offhand but I had a Pearl 33 Phaser that had 18v input, that component was faulty. I suppose tracing from point of entry (power) may be best.
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Re: KORG Mono/Poly fuse - what kind of capacitor is that?

Postby fuzzbuzzfuzz » Fri Jan 12, 2018 9:26 pm

...and I'm sure you changed that fuse shown right? (just in case) ;)
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Re: KORG Mono/Poly fuse - what kind of capacitor is that?

Postby Pepe » Sat Jan 13, 2018 8:54 am

I replaced all the fuses. The power supply seems to work well on its own without anything connected to it. I have already sent a mail to a former forum member who also helped me a lot with the repair of my KORG Trident that finally is properly alive again since yesterday!
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