Kawai rep

[Guest]

I am trying to troubleshoot the expression pedal on a Kawai E90. Does anyone have a service manual for this model to send me a copy of the relevant section to go by ? Is this unit interchangeable with the pedal unit from a Yamaha B5Br ? They appear identical.

[andyg]

Re: Kawai rep



It's very unlikely that the pedals are interchangeable. Most expression pedals on Japanese organs look the same! The usual problem with old Kawai expression pedals is the potentiometer inside, that starts to fail or gets dirty. The symptoms are usually sudden jumps in volume, or volume that's stuck on maximum or minimum. If you can find the value of the pot, it is possible to disassemble the pedal and change it. The value may be stamped on the pot itself.</p>

Andy
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[Guest]

Re: Kawai rep



Thanks Andy - It's interesting that this is not a total loss of volume, just it has MINIMUM volume, and doesn't respond to change. Your explanation appears spot on !</P>


I'll look further.</P>

[John Kinkennon]

Re: Kawai rep

Hi! I did a quick search on the internet and read something to the effect that this unit uses a lamp in the expression pedal circuit, presumably along with a LDR or something similar. Can't vouch for the accuracy of that, but the person represented himself as being an organ tech. Anyway, it would be worth a look to see if there is a removable lamp that is burned out. Seems like my old Yamaha used something similar in a touch-vibrato circuit on the little "synth" keyboard.

[andyg]

Re: Kawai rep



Pretty sure that model used a pot rather than a bulb and LDR. It was a current model when I joined Kawai in 1976 and we did had a few problems with expression pedal pots at that time. Later models were better behaved.</p>

Worth checking though, as the bulbed ones are usually a doddle to fix.
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Andy
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[JerryG]

Re: Kawai rep



I have to ask:</P>


What's a "doddle"?</P>
<P mce_keep="true"></P>

[andyg]

Re: Kawai rep



Sorry, that one didn't survive transatlantic translation! [:D]</p>

A doddle = something that's really easy.
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[John Kinkennon]

Re: Kawai rep



Sorry, Andy. I definitely defer to your experience with this model. Always enjoy your posts, but forgot you had a connection with Kawii.</P>


John</P>

[Guest]

Re: Kawai rep

Hi Andy, I've stripped out the expresion pedal, and found it has a lamp,(8V, 0.15A ) which exhibits continuity, and appears to be intact. I have no voltage source to suit to check it out, but on re-assembly, the volume is noticeably improved, although nowhere near adequate for the job required. I couldn't identify what you term the LDR - there was what I could best describe as a fine mesh covering a hole in the lamp chamber. Is this some type of light receptor ? I was wondering if the dissembly/ assembly cleared away some accumulation of dust to account for the improvement. It is VERY dusty inside the cabinet, but i hadn't time to clean it out properly. If you think this is possibly the problem, I'll go back in and clean it up. I just couldn't identify a likely "cell" other than this mesh. What should an LDR look like ?

[Guest]

Re: Kawai rep



An LDR is an input transducer (sensor) which converts brightness (light) to resistance. It is made from cadmium sulphide (CdS) and the resistance decreases as the brightness of light falling on the LDR increases.</p>

On some of the older computer peripherals I used to work on the primary malfunction was the lamp. Even though the lamp has continuity and appears to be functioning (the lamp is lit) there is a diminishing output from the lamp due to metal deposit on the interior of the bulb thereby reducing the lamp output. That changes the resistance from the sensor which in turn affects the volume. What little volume change you experienced was most likely due to removing the dust/dirt that accumulated on either surface.
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Change the bulb.
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[Guest]

Re: Kawai rep

OK - Thanks, I'll try to get hold of one.

[andyg]

Re: Kawai rep

Well, I stand corrected on that one, but maybe it's an original E90 (they used the number more than once) from the mid 70's (before my time). Changing the lamp is the first and easiest course of action, if that doen't work then you'll have to find an equivalent LDR.

[Guest]

Re: Kawai rep



Thanks Andy,</P>


I went back in today and found one wire from the LDR (yes, I identified it) was broken but apparently still touching. The insulation crumbled, so I replaced the connection. I'm trying to source a replacement bulb, even though the existing one does work. I'm having trouble though - maybe they're not too common in Australia. I've cleaned the interior up, not that it made any difference. I've about half volume at the moment. I'll keep you posted. Thanks for the help.</P>


PS My next post will probablybe about my Casio WK1600 - the numeric pad in malfunctioning - possibly a circuit board - I don't know !.</P>

[Guest]

Re: Kawai rep



Andy, couldn't identify the LDR type, tried one of only 2 available, suggested by the supplier, and recommended by a tech as used on a yamaha. No response from the pedal at all. I now have half volume on the upper manual, quarter volume on the lower manual, and very little on the pedal range.</P>


I've just about gone as far as I'm game to go (beyond my capabilities I'm afraid). so it looks like it's destined for the scrapheap. Such a shame there's little support from the manufacturer at this age of unit.</P>


I appreciate the help you've given me.</P>

[andyg]

Re: Kawai rep

[quote user="Barry Carter"]

Such a shame there's little support from the manufacturer at this age of unit.</p>


[/quote]</p>

It is over 30 years old now, possibly nearer 35, so lack of spares is pretty common. It's not a Kawai bespoke part, so you're in the hands of the original parts supplier rather than Kawai. Most organs over 15 years are getting difficult on spares now, and some makes don't go back more than the 'required minimum' period.</p>

There probably is a way around it, by replacing the LDR with a swell pedal mounted pot of similar value.</p>

I hope this won't put you off playing or learning the organ, as there are hundreds of small organs out there being sold for pennies or given away, so you're sure to find something to suit.
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Andy</p>

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