On 27 Nov, 22:10, Prisoner at War wrote:
I have a two year-old Yamaha P-90 and I occasionally trip over the
power supply line. It only happens four times a year or something, so
I've really never thought anything of it.

Today, however, the keyboard wouldn't turn back on when reconnected!!
And it's not the outlet or the extension cord I use, that's for sure
-- so either the AC adapter got messed up, or...my keyboard is toast!!

I looked in the manual but there's no address for a service center at
all! I also tried googling, to no luck so far...the company I bought
the P-90 from, Musician's Friend, doesn't have anything about this
kind of situation in their online FAQ...in a worst-case scenario, what
do I do to get this thing fixed?

I've never had a broken keyboard before...but I suppose any ol'
neighborhood TV repair shop can fix it?? I'm assuming it's an
electronics issue, having to do with sudden loss of power...I don't
understand the physics of it, but it seems to my layman's
sensibilities that that shouldn't be catastrophic at all...I mean,
turning the thing off by hitting the power button is the same as
suddenly unplugging it by tripping over its adapter cord, isn't it???

Any advice, thanks in advance! (Any sarcasm, please be witty at
least.)

This keyboard has an external wall-wart power supply doesn't it? These
are standard Yamaha items - I bet it's one of these:
http://www.dv247.com/invt/8113/
... or whatever the equivalent is in your country.

I really, really doubt the keyboard itself was damaged, it'll be the
power adapter and while these can be repaired, few people would
bother. Certainly getting someone else to repair it for you would cost
more than the price of a new one.

TWJ