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Replacing Korg MS-10 internal transformer (100v to 240v) Modular Synthesizers
Old 1 week ago
  #1
Gear Nut
 
mogazi!'s Avatar
Replacing Korg MS-10 internal transformer (100v to 240v)

Hello,
I'd like to replace the Japanese internal transformer of my Korg MS-10 with a 240v one. Judging from the schematics (see picture) the transformer is a simple 36v centre tapped to get +/-18v which then gets regulated down to 15v...

However when measuring (unloaded) the transformer currently in the unit, I found it to be a 60v centre tapped to get +/-30v! I know that unloaded measurement is not an accurate representation of a transformer actual voltages but I was under the impression that the difference is generally about 5~10%...
Not almost double!

Is there any particular reason why Korg would have wanted to have around 30v on input only to make the regulators to work that much harder to slam it down to 15v?
Maybe (probably) I'm missing something here...

Any advice?

Replacing Korg MS-10 internal transformer (100v to 240v)-screen-shot-2019-02-13-12.42.15-pm.png
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Replacing Korg MS-10 internal transformer (100v to 240v)-screen-shot-2019-02-13-12.42.15-pm.png  
Old 6 days ago
  #2
Lives for gear
 
Radardoug's Avatar
 

Just replace it with an appropriate transformer of the same size, 18 volts aside, 1A to 2A.
Old 6 days ago
  #3
Gear Nut
 
mogazi!'s Avatar
Thanks for the reply!
In actual fact I found out elsewhere that the transformer is actually a multi-tap primary!

A bit of further investigation and turns out this is the same transformer used on the MS-03. On the MS-10 any details about the transformer are omitted but n the MS-03 manual it clearly states that this transformer KA-680 is tappable for "100v, 220v and 240v".
I didn't take apart the whole unit but on closer inspection, just behind the fuse holder area, neatly tucked away and wrapped on themselves are two other taps! :o

I'm told the wire colors correspond to the following:
Brown wire for 100V
Orange wire for 220V
Yellow wire for 240V

So it should be as easy as rewiring the primary. I'm told though, that I should replace the fuse as well. Right now all I can see on the manual and the synth itself says "0.5A 250V" which is what I have already in there now...
Old 6 days ago
  #4
Lives for gear
 
Radardoug's Avatar
 

Well spotted! That makes it much easier.
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