I avoid keyboards whenever I can. They are heavy, have too many screws in,
and take up too much bench space. On this occasion however, I was asked to
look at a Korg LP-350 electric piano by a music store that I have only
recently started doing work for, so had to be 'accommodating' to ...

The shop owner said it was dead, and that he had tried another power supply
already. I figured that this might be something nice and straightforward
like a socket busted out of the board. When it arrived, I was delighted to
see that the socket and on - off switch were located in a largish 'pod'
secured to the bottom of the unit with just 6 screws. So I stood the unit
vertically, leaned against the bench, and removed the pod. In fact, the
entire electronics seems to be on a single board in this enclosure, with
just the keyboard itself and the control switchery being in the main part of
the cabinet. The problem turned out to be some miniscule little sm device in
series with the DC connector centre pin. It is too small to have any value
marked on it, but does have the designation "R" on the board so maybe its a
tiny safety resistor (anyone know ?)

So to get it going initially and check for any other problems, I hung a 1
ohm fusible R across the pads. This restored life to the LEDs on the control
section, so I hooked it to an amp. And this is where it got odd - for me at
least.

Some notes sort of worked, although you had to pound them quite hard. Other
notes didn't work at all. Then when you went back to one that worked a few
seconds ago, now it didn't. Clearly, it's a keyboard with full velocity
sensing, but this seemed very arbitrary as well. My heart was just beginning
to sink when I decided to turn it 'right way up' i.e. horizontal, just in
case. And Lo! Then it all worked. Every note was fine, and the 'touch'
behaved perfectly. Now I don't pretend to understand keyboards, but as far
as I can recall, all the ones that I've previously seen have either been
based on bus bars and springy contacts, or rubber keymats.

So how is this one done such that it won't work when the unit is standing
upright on its end ?

Arfa