Pre-switch-on advice for some vintage Korg synths

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liveinabin
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Pre-switch-on advice for some vintage Korg synths

Post by liveinabin » Fri Apr 30, 2021 2:46 pm

Hallo all. Long time listener, first time caller.

I'm about to be given (given!!) a Korg MS-20 mk2 and an MS-50. I can't believe my luck.
Now, they're my first vintage synths so I've little experience. I do, however, fix up old computers and consoles for fun - and from my experience in that, I'm naturally wary of turning these things on. They are from a house clearance and haven't had a good life.

I have looked at the service manual for the MS-20 and there are a bunch of electrolytic capacitors, as well as a couple of the dreaded tantalum caps. Now I don't want to change the sound of this great synth, but I've known too many computers that have died because that dodgy old cap in the power supply fried all the chips on first power up.

Is there anything I should just replace straight away or am I being too cautious?

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madtheory
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Re: Pre-switch-on advice for some vintage Korg synths

Post by madtheory » Sat May 01, 2021 8:39 pm

Lucky you!

If you know how to recognise and test for failing electrolytics and shorted tantalums, go right ahead and replace them.

The electrolytics in these Korgs reached end-of-life about 20 years ago, they were not a good quality part in the first place. Replace like with like, observe polarity. You can use a higher voltage rating but keep mF the same, check your sizes in mm before replacing, some are radial, some are axial.

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Yekuku
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Re: Pre-switch-on advice for some vintage Korg synths

Post by Yekuku » Sat May 01, 2021 9:37 pm

MS-series admirer here , I have worked on a few and I would say that they are the most reliable vintage synths.
Depending on how heavily they were used , you might need to replace the electrolytics.
I have a KEIO MS-20 mkI with all the originals caps that operates according to factory specs, it looks pristine ,it was certainly not used much .
More heavily used MS-series gear exhibit "leaky" electrolytics with a deformed top, not exactly blown more like bulged, and they usually measure 20% more capacitance than they should. They dont do any critical harm but they can cause "drifting" which sometimes is accepted as vintage character.
I have never seen a bad tantalum in an MS synth, but I have seen bad voltage regulators (7915,7815), opamps (4558) and FETs (2SK30Y)
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liveinabin
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Re: Pre-switch-on advice for some vintage Korg synths

Post by liveinabin » Sat May 01, 2021 11:11 pm

Superb. Thanks to both of you. I haven’t had a look at these synths yet but I suspect a bad life in poor conditions, being forced to make bad techno :)

I’ll certainly be looking closely at the caps. As for the power regulators, on old computers it’s usually customary to replace them with efficient newer models for reliability (and much less heat). Is this a done thing with synths?

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Re: Pre-switch-on advice for some vintage Korg synths

Post by Yekuku » Sun May 02, 2021 8:31 am

The 78XX and 79XX series of voltage regulators are still used in new gear, I would not substitute them as history showed that they work great in these products.
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liveinabin
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Re: Pre-switch-on advice for some vintage Korg synths

Post by liveinabin » Sun May 02, 2021 8:52 pm

Fair enough. Thanks. I guess the problem of heat from old style regulators isn’t as bad in a cavernous thing like synth.
It plays havoc in the closed case of a Sinclair ZX Spectrum though :)

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