Electronic keyboard repair

[Dave Nereson]

----- Original Message ----- 
From: "Richard Moody" <remoody@midstatesd.net>
To: "'Pianotech'" <pianotech@ptg.org>
Sent: Thursday, July 22, 2004 11:59 PM
Subject: RE: Electronic keyboard repair


 > The keyboard in question is a Yamaha PSR 340.
> the plug is from an AC to DC converter.   I need to remove the
> receptacle (which I referred to as 'extract the power input') of this
> plug from the keyboard because I think it was damaged when the "dog"
> stumbled over it for the fourth time .     It is a common ac-dc input
> like lap tops, cordless phones, scanners etc. ---ric

    If it's less than 20 years old or so, most likely the jack, or
receptacle, is soldered to a small PCB (printed circuit board) with 4 prongs
or so, typically 2 to solder it to the board and the other 2 being the
conductors.  I imagine you remove the top (search for screws), look inside
along the back wall, and see where the power cord comes in and whether it
has a jack soldered to a board.  It may just have a cable clamp after which
it goes to a board somewhere.  Probably the soldered prongs are underneath
and you'll have to remove the little board to get at 'em.  Look for screws
that hold the little board to the case.  It could just as well be the big
main board, depending on the model.  But if you can get to the prongs of the
receptacle or at least see how it's mounted, maybe you can see if any wires
or traces on the board are broken.  Draw a little diagram, no matter how
simple, because if it's apart for a few days or weeks, you may forget which
color wire went where.
    Now, even if you get the receptacle off, you may not be able to buy the
exact replacement at an electronics store.  You may have to order the whole
little power input board or whatever it's called on that model.  If it's a
common jack, you might be able to order it online from Digi-Key, Mouser,
Newark, or maybe even Radio Shack.  But if you have to get the whole board,
you'll have to order it from the manufacturer.
    It hard to try and unsolder things that have more than two terminals,
unless you have a desoldering tool, which is a plunger, or "sucker" that
sucks up the solder while it's molten -- they have 'em at Radio Shack.  It's
like the opposite of a tiny bicycle pump or cake decorator.  If it's mounted
to a PCB, use a low-wattage pencil-type soldering iron.  If you have the
whole unit loose from the case, sometimes you can melt the solder from a
terminal and immediately shake it towards the floor to make the solder fly
off.  Do that to all the terminals, then see if it'll come loose.  Don't do
any of this if it's still under warranty.  In fact, maybe you should leave
it on there and contact the manufacturer first to see if you can get the
board it's mounted to.
    I'm not sure what to tell you from here.  Some keyboard are quite
complex inside and others quite simple.  I'm not familiar with this
model.....        --David Nereson, RPT