Transformer at MS-10

[Harry Bissell]

Try signaltransformer.com and check out some of their transformer designs for
bipolar supplies (+-15). They have special windings for this use as well as
tips on the right regulators.  Check out your regulators and match them up with
theirs, that'll point you to the right transformer. It'll probably cost $20 but
its worth it.

They also have competitors (microtran, etc...) that make direct subs for their
parts... but since they publish the neat design guides I go with them, and the
competition isn't that much less in price.

You need about 18VAC to run a 15V regulator chip, so a center tapped 36 volt
transformer is probablt right. I don't recommend the resistor trick... it makes
for a "ground" point that isn't really firm... It can work in a circuit that
draws very low power, or one that has very big filter caps... and it doesn't
stay centered if the current draw isn't equal on both plus and minus (and it
often isn't). The resistor divider eats up power if it is low enough in value
to overcome these shortcommings.  This is probably why Korg didn't go that way.
It "can" be used for low power circuits like stomp-boxes if the designer knows
what he's doing. You should avoid it. Try to copy the original design with as
little change as possible unless you really are sure of yourself... it'll save
you time and money in the long run.   Good Luck Mr. Phelps
:^) Harry

RoBot wrote:

> I recently bought a Korg MS-10 at a flea-market for about $60 ;)
> It's in perfect condition, except from that I think that someone have fried
> the 110V transformer with 220V "European power" and some other components.
> Now my question for all MS-owners:
> At Hyperreals MS-20 schematics there's 18V with regulators for +15V/-15V.
> How many volts is the original transformer at?
> Could it run with a 15V 400mA transformer?
> I have a transformer without the 0v common ground connection, so I'm
> planning to make one with resistors (tip from a friend), but I don't know
> how many mA's the main board needs.. Any tips?
>
> I've checked the net for some basics in AC/DC converting, but without any
> useful results, and my electronic skills are limited to simple ttl, so
> maybe you can help..
>
> Thanks,
> Martin