I'm a little green on keyboards so I don't know if this is a weird probem or what, I find it insteresting though.

When you play F sharp it also plays F.
When you play A sharp it also plays A.
When you play D it also plays D flat.

This is on all octavs both upper and lower, BUT not the pedals. Also on the lower board these keys sometimes repeat themselves. Also on the lower if you play the A sharp and the F sharp together they kinda appregriate. (sp)

Any ideas ? Since it is all octaves I am thinking maybe the micro or some little diopdes near it, or do these things have a chip in between the board and the micro to scan it ? And possibly the pedals are a different system so they are unaffected ? I think it only has like 14 keys or something like that down there.

I wouldn't mind knowoing more about the architecture of these things. (or do they call that topology now)I mean, some of these keboard, we are talking full 88 here, I can't believe how few wires go to the keyboard itse;f, especially when the thing is 24 note polyphonic.

In the old days I was in a keyboard and there was a wire for each key going to taps on a bank of 11 boards with a big coil on each one, adjustable of course for tuning. No master oscillator and divider chain.

Nother thing I wonder, working on these (relatively) cheap keyboards, am I going to find the innards of the really good ones similar ? Or are they simply a whole new ballgame.

wrote in message
...

I'm a little green on keyboards so I don't know if this is a weird probem
or what, I find it insteresting though.

When you play F sharp it also plays F.
When you play A sharp it also plays A.
When you play D it also plays D flat.

This is on all octavs both upper and lower, BUT not the pedals. Also on the
lower board these keys sometimes repeat themselves. Also on the lower if you
play the A sharp and the F sharp together they kinda appregriate. (sp)

Any ideas ? Since it is all octaves I am thinking maybe the micro or some
little diopdes near it, or do these things have a chip in between the board
and the micro to scan it ? And possibly the pedals are a different system so
they are unaffected ? I think it only has like 14 keys or something like
that down there.



Don't try and overcomplicate the problem. Think Occam's Razor. (Google
that if you're not familiar)

The keyboard is scanned in rows and columns. So you have a 2D grid where
each key will uniquely connect one row with one column (via a diode on each
key)

What tends to happen, in the real world, is that stuff gets dropped down
into the keys and onto the key contact PCB. Beer, sweat, other bodily
fluids etc. Yuk.
This often results in some of these rows and columns being shorted together.
Which might explain why your F key also plays an F# etc.

Take out the keyboard contact PCB, and you will probably find it is full of
****e and corroded to f@@k, and that one of those corrosions is causing a
short between one of those row and column lines, thus the F and F# keys are
shorted together. It doesn't even need to be a short, just enough to
cause the scanning IC to decide 1 or 0 in error.



Gareth.

I have only come across this once, but I did find a Korg keyboard with notes
not triggering that I tracked down to a shorted LED on the front panel.

Turned out the cheapskates had used the keyboard scanning chip to also scan
and power the LEDS and switches on the top panel.

One shorted front panel LED caused one of the Column/Row lines to also be
partially shorted, thus causing many of the keys to malfunction.



Again think Occam's razor.



Gareth.

Thanks. I am familiar with Occam's - the simplest explanaton is usually right.

"Take out the keyboard contact PCB, and you will probably find it is full of
****e and corroded to f@@k, and that one of those corrosions is causing a
short between one of those row and column lines"

Thing about that is it is all octaves. That means it has to be just a bit downstream. But the fact that the pedals don't do it would steer this away from the micro really, unless I find that to be totally separate.

So I am not looking so much under the keys, I assume I am looking more toward the board. Or am I wrong ? I mean, can some conductive gook just under one of them screw with all the octaves ?

And I gotta laught just a bit. They way you wrote that, it makes it sound like beer is a bodily fluid. LOL I know people like that.

I'll get to tearing into the thing next day or so. Let them get over their celebration because I got their Farfisa fixed. Another Italian ting nobody ever heard of.

But back to the subject, the fact that in each of these three faults the keys are right next to each other. That is telling me someting I just have to mull it over a bit. Whatever conductive crap or corrosion it has, has to be in certain positions.

Hmm, I used to have a Panasonic login. I'll have to see if I can find it and if it still works. But maybe, ...

OK, it must scan by octaves though both boards for this problem to be possible. I think it is about five octaves per so that means 11 lines for the notes and 10 for the octave selection. Maybe 20 wires. I need to look where they all come together.

I'll let you know.

Thanks.