Kelly and Sandy said:
I have a 5-octave Yamaha Portatone PSR-220 (touch-sensitive keys).
It's four or five years old. I'm writing from England.
Dear Me,
My Yamaha Portatone is now fully functional again. Turned out that
the touch-sensitive part under the keys needed cleaning out (I used a
photographers brush, and then just blew hard). A lot of tiny bits of
detritus, crumbs, fluff, God-knows-what, had collected, and finally
upset the capacitance mechanism for one of the keys.
Here is how I got at the keyboard, and the keys... especially the
row of "circuit-board-etched" capacitances, and mats of rubbery pads
under the keys that go to make up the Portatone's touch-sensitive
system:
1) Turn over the Portatone, placing it on a large pillow (otherwise
it puts pressure on the volume knob). With a small Philips
screwdriver unscrew the seventeen or so screws from the bottom
cowling shell. Three are longer than the rest, by the way. Put
all the screws into a cup labelled (mentally or literally) "Bottom
Cowling". Remove the bottom cowling and put it aside.
2) You are now looking at the insides of the Portatone. Arrange it
so that the keyboard of the Portatone is away from you -- at the
top of the page, so to speak. You will notice that there are two
connectors from the keyboard to the rest of the circuitry. One is
a two-wire power supply. (And the other is a four (or five? can't
remember) wire ribbon cable. The ribbon cable does not need to be
disconnected to access, or to remove the keyboard unit from the
Portatone). The power cable goes from the Printed Circuit Board
mounted on the keyboard and ends in a neat little white plug on
another PCB in the Portatone, which can be simply pulled out.
So therefore, now disconnect the keyboard power wire from the rest
of the Portatone, by carefully pulling out the plug end located on
the other PCB. (Don't worry, there's only one way round the plug
can be pushed back in.)
3) This PCB has to be free, to allow the touch sensitive mechanism to
be accessed. There are two little philips screws holding the PCB
onto the rest of the keyboard unit. Remove 'em, and put 'em in a
cup labelled "Keyboard PCB Screws".
4) You now notice the long thin board (two boards, in fact) of PCB-
like material running the length of the keyboard. Even under the
ribbon cable connectors, you can make out little glass-encased
diodes or whatnots all along the length of the board(s). We have
to remove this "strike board" (actually a unit of two boards,
ribbon-cabled together). Now with the Portatone keyboard still
"at the top of the page", you'll notice on the "top" side of the
strike board unit, little plastic "teeth", or holders, engaged as
hooks to keep the strike board held tight. And along the bottom
side of the strike board, are also "hooks", but saw-tooth shaped,
and mounted on plastic springy gizmos THAT CAN BE PULLED BACK TO
RELEASE their grip on the board.
The trick to getting the entire board unit out is to -- starting
at the outside of the keyboard -- push back a springy thing with
your finger and then lifting up the strike board, past the saw-
tooth on the spring thing, so that it doesn't engage again when
you let go. You then release the next springy thing, and the
next, and so on. Very quickly you have half the board fully
released. Do the same for the other half, working from the
outside of the keyboard in, to the centre. Now the keyboard is
freed from the strike-board unit. (The strike board and it's PCB
is attached to the rest Portatone via a ribbon cable.)
5) This situation now reveals a row of rubbery (bluey-green?) mats
where the strike board was. Five mats, on my 5-octave Portatone.
Each mat has 12 "pockles", "button things", "plops", call 'em what
you like. There's also a small, individual, end-mat (orange)
corresponding to the lone high C at the top of my keyboard. The
octave (12 pockle, blue- green) mats are identical to eachother.
Remove them.
[See 5a) below, "Getting to the keys of the keyboard", if at this
stage you want to get to the actual keys of the keyboard.]
I gave "pockle mats" a good cleaning with a soft dry photographers
brush, and (since I don't have a can of liquid air) several good
percussive blows of breath with pursed lips. I couldn't see
anything physically wrong with any of my "octave" mats, but I
still rearranged them when putting them back. I moved the base
octaves to the treble, and vice-versa.
Putting back the pockle mats takes some care, as the pockles for
the black notes tend to mis-seat themselves if you're not careful.
And then they won't play properly (much stiffer!) if they're not
seated right. Luckily, you can run along the length of the mats
by eye, checking for bad seating of individual pockles, and
smoothing and adjusting with your fingertips. Once the mats are
back right and flat, try not to depress the keys of the keyboard,
until the strike board has been firmly clipped back -- or you'll
risk mis-seating pockles again.
6) Turning back to the "strike board": Clean all the crud from the
row of capacitance "swirls" etched onto the PCB of the strike
board. In my own case, it was a piece of crud that had changed
the capacitance of one for the keys so that it started to
malfunction intermittently. To be honest I think it was a bit of
parmesan cheese, by the looks of it! Anyway, clip back the strike
board over the -- well-seated -- rubber mats. The springy things
make a satisfying "click!" when they engage the strike board.
Make sure they've all clicked, they're ALL engaged, and the strike
board is firmly back in its place.
7) OK! REASSEMBLE! That means screw back the keyboard PCB into
place on the keyboard, and then the cowling, and it's seventeen
screws. Et voila!
- - - - -
5a) Getting to the keys of the keyboard.
Remove the two (for me) screws holding the keyboard to the rest of
the Portatone. (Yes, put them in a special cup of their own.)
The keyboard is now entirely free of the rest of the Portatone.
Turn the keyboard over with the black and white keys showing, as
if you're going to play.
Before we start unscrewing things, let's realise something. Apart
from the top C key, the keys are arranged in identical sets of
octaves: the black keys, (C#-D#, F#-G#-A#) form one complete set
of plastic moulding. The white keys D-F-A form another set, and
the white keys C-E-G-B form another. These three sets of plastic
mouldings overlap and interlink to form one octave. To recap
then, one octave unit is made of two white sets and a black set of
plastic mouldings.
OK. Unscrew ALL the screws along the top -- ie the back -- of the
keyboard unit. (You can't get at just one octave, without
dismantling all of them.) Note that every screw position is
conveniently marked by arrows > <. (A special cup of their own,
please.) I forget from which end, low end or high end, but by
pulling up, and then towards you, on a set of black keys (C#-D#,
F#-G#-A#), you can now remove all the sets of black keys. You'll
see that little notches at the backs of the sets keep them in
place when in the keyboard. (For me -- even though some of them
had different numbers -- the sets are all identical and
functionally indistinguishable from one another.) You can then
remove the single top C key. And then the D-F-A sets, and then
the C-E-G-Bs. Take care with the lubrication grease now exposed
on the keyboard skeleton. I found no difference between the sets.
That's to say, all my octaves are interchangeable. After cleaning
(with spit and cloth), therefore, I rearranged the octaves around,
putting base octave up the top, and high octaves lower. And now,
REASSEMBLE! (Where are those cups now, eh!?)
With kind regards,
Sandy
