Vintage Synth Explorer Forums

Posted parts of this a couple of days ago in the "show-n-tell projects"-thread. Guess it's more of a help topic really.

Kawai S-100F: Took apart the S-100F in order to fix the 13 leftmost keys which are triggering some pretty interesting notes. Found out the keys match the 13 contacts on this "box". Can't figure out how to open the thing without breaking it though, so I'm kind of stuck


Kawai S-100F: Same part seen from the opposite side. Anyone know what this part is called? Or if it's fixable at all? I'm guessing it will be nearly impossible to find a replacement, but you never know...


Searching google for 450R9124/45OR9124, as printed on top of the enclosure, obviously didn't give any results.

Anyone?

I have a gut feeling that the problem isn't there. Is that just the housing for the keys?

Thanks for replying. Not sure what you mean by housing for the keys (language barrier), so I took these snaps to illustrate how the keyboard works. Obviously neither the keys nor the contacts are mounted properly here.



Any idea where the problem might be?

The reason I'm thinking the 45OR9124 is faulty, is that only the 13 keys corresponding to the 13 contacts on the 45OR9124 make strange notes*. The rest of the keys which are split between two 44OR9124 contact boxes are fine. And they all get power from the same connector from the main board.

*sounds like a combination of a contact not quite making a proper connection, like a flickering neon light, and an inconsistent note.

found a schematic if you need one.

looks like the keying is simple N.O. contacts with a string of 47-ohm resistors: +4 volts at top, GND at bottom.
if the keyboard is in sections, how about the connections BETWEEN the middle and lower section?
there is a keyboard scaling circut with an op=amp...maybe this has failed and the lower notes are 'falling off the edge'.

looks like a cool little mono. Good luck with it!

Late reply... too many projects going on at once.
Thanks for replying and for the schematic, it's much better resolution than the one I had.

rhino wrote:looks like the keying is simple N.O. contacts with a string of 47-ohm resistors: +4 volts at top, GND at bottom.

Not sure what you mean by N.O. contacts.

rhino wrote:if the keyboard is in sections, how about the connections BETWEEN the middle and lower section?

The keyboard is in three sections, the upper section (~the higher notes) is the failing one. I've done continuity checking between sections, and I believe the connections are fine.

rhino wrote:there is a keyboard scaling circut with an op=amp...maybe this has failed and the lower notes are 'falling off the edge'.

Trying to locate that op-amp. Guess it couldn't hurt changing it?
Oh, and it's actually the higher notes that are problematic, not that it matters really , just to make it clear.

rhino wrote:looks like a cool little mono. Good luck with it!

Thanks. It's certainly fun to play!

still think there a problem with electrical flow from one section of keys to another. try measuring the output voltage from the keys as you play up and down the notes. the highest note should be aroung 4 volts and get lowere in a smooth manner down from there.

ok. i've had time to think about this.
you're saying that the TOP octive of keys makes strange noises: can you describe these sounds?

two thoughts:
1. the oscillator circut has changes (aging componets) and cannot sustain correct oscillation at higher notes.

2. the gate circut that detects the keyboard control voltage and cues the ASDR is not reacting to the signals from the top octive

3. is there a "keyboard scaling" mod path? maybe this is causing the problem

Thanks Rhino, your troubleshooting help is much appreciated.

1. There's no doubt that this synth has seen better days. Osc circuit may very well be affected by aging, but as keyboard behaviour doesn't change when VCO RANGE is switched and as notes only (mostly) change upon keys being released, I believe the problem must be the gate circuit or the keyboard mechanism.

2. Possibly. It is reacting though, just not always quite right.

This clip shows how some notes change after the key is depressed.
[youtube]EMNaHsYRtks[/youtube]

Hello, I thought I'd bump this old thread with a question that at first glance might be somewhat simular.

I am the proud new owner of an old Kawai 100F in what seems to be a good shape. Sounds awesome, works like a charm, has no mods and actually show no previous signs of having ever been opened before.
Now to the problem

The synth is out of tune, a few cents between each note, ads up to about 17-20 cents between the A on the first octave but as higher up on the octaves I go, the more out of tune it becomes and the difference between the A on the first and last octave is almost 2 tones!!! I have some limited experience with other analog synths and opened it up to look for the "tuning pots" that I have in another synth but couldnt find any.

Is this a sign of old parts, problem with electricity or should I look harder for those pots?

best
Karl

I have the same problem getting to the key contacts (want to clean em). Has anyone (or even the thread opener) finally managed to open that box ?
thankyou, soda