I am new to this forum so tell me if I am in the wrong place. For a while now I have been finding broken keyboards free or very cheap and fixing them to give away just for something to do. Quite often they end up in the dump but also some only have simple faults. At the moment I have a Kawai CA 970 which has been looked after very well but just stopped working. I know old keyboards are not worth fixing but I like a challenge and my labour is free. Does anyone collect and resell old PCBs. This one needs the main board KEP-073. It seems a pity to dump the whole thing and my electronics expertise is not good enough to try to repair this. Power supplies and other electrical faults I have managed in the past. Thanks for reading.
Kawai CA970
- Thread starter Richard45
- Start date
Hi Richard, welcome to the forum. It sounds like you have much the same ideas about older keyboards etc., as myself. I hate to dump anything old that is not working without making a determined effort to repair it, if at all possible. Having said that, sometimes an item is just not worth the trouble and expense, especially if it is a cheap throwaway item to begin with but that's not the case with your CA 970.
How did you determine that the main board needs replacing and by "not working", do you mean it's not even powering on or just not producing any sound? Does the display and LED's light up as normal? Also, does your "electronics expertise" include troubleshooting, using a multimeter and soldering/desoldering? I don't claim to be an expert by any means but I have had success with quite a variety of keyboards over the years. Any information you can give might help to point you in the right direction to get it working again.
Regards, Al
Thanks Al, When I got it, it powered on, all the leds lit up as normal and you could press the buttons and the screen showed what it should. It looked like it was working but just no sound as if the headphones were plugged in. That wasn't the case and the headphone jack was not killing the sound. In testing I could connect my turntable (line out) to the line in and the sound was perfect from all 4 speakers but, of course on full volume as this was after the volume pot I guess. I visually inspected the other 2 boards, both OK to look at and no bad connections. Unfortunately with my mucking about, now it does not even do the above. I used to get the relay to click on power up. Not any more. I get 4.9V (not 5V) from the lead leaving the PS board but that was always the case. Ask me any other questions if you like.
Okay, it's probably a mute point now (excuse the pun: mute:- no sound) when you confirmed there was no headphone jack plugged in, did you try actually using headphones? The reason I mention this is that in the last two weeks, I decided to set up my Yamaha CP300, which had been stored in its road case for about 4 years. It had worked perfectly the last time it had been played but I couldn't get any sound from it at all, not even the demo songs worked.
Well, it turned out that the headphone jack contacts were dirty and after rapidly pushing and pulling the plug in and out a few times, everything was back to normal. I also sprayed inside with Deoxit to prevent further issues later on. I had the same no-sound symptoms with a Roland KR575 and the problem was that our cat had partially chewed the cable which ran from the 3-pedal unit at the back of the piano. After repairing it, the sound was back again.
I don't know if either of those two examples are any help to you now but during your probing around inside, is there a possibility that one of the connectors you checked is not seated properly? You can verify good connection of a ribbon cable by confirming continuity from the back of each plug contact to the back of the corresponding plug contact on the next board.
Ideally, you need a copy of the service manual which should show voltages at various test points on the circuit diagram. Normally, I can find free pdf copies online from various sources but unfortunately came up with a blank for your model. The best I could find was here https://www.wdgreenhill.co.uk/product-page/ca770-ca970-service-manual for a modest sum in pounds sterling. It's for a download copy so if you decide to buy it, you'll receive it very quickly.
The 4.9V you mentioned is probably ok, assuming it should be aroung 5v but there probably should be other DC voltages leaving the PS section as well (check for blown fuses). Also check for positive and negative voltages at the voltage regulators, as they are sometimes prone to failure and are usually cheap to replace, if you can solder them yourself. Surface Mount capacitors (the small ones), along with larger ones can sometimes fail and there are quite a few YT videos showing how to replace them.
I hope this gives you some help in finding the problem(s).
Al
Well, it turned out that the headphone jack contacts were dirty and after rapidly pushing and pulling the plug in and out a few times, everything was back to normal. I also sprayed inside with Deoxit to prevent further issues later on. I had the same no-sound symptoms with a Roland KR575 and the problem was that our cat had partially chewed the cable which ran from the 3-pedal unit at the back of the piano. After repairing it, the sound was back again.
I don't know if either of those two examples are any help to you now but during your probing around inside, is there a possibility that one of the connectors you checked is not seated properly? You can verify good connection of a ribbon cable by confirming continuity from the back of each plug contact to the back of the corresponding plug contact on the next board.
Ideally, you need a copy of the service manual which should show voltages at various test points on the circuit diagram. Normally, I can find free pdf copies online from various sources but unfortunately came up with a blank for your model. The best I could find was here https://www.wdgreenhill.co.uk/product-page/ca770-ca970-service-manual for a modest sum in pounds sterling. It's for a download copy so if you decide to buy it, you'll receive it very quickly.
The 4.9V you mentioned is probably ok, assuming it should be aroung 5v but there probably should be other DC voltages leaving the PS section as well (check for blown fuses). Also check for positive and negative voltages at the voltage regulators, as they are sometimes prone to failure and are usually cheap to replace, if you can solder them yourself. Surface Mount capacitors (the small ones), along with larger ones can sometimes fail and there are quite a few YT videos showing how to replace them.
I hope this gives you some help in finding the problem(s).
Al
Hello Al, I jiggled the headphones in the headphone jacks when I first got it. I only just now took that little board out and the only components on it are 4 resistors, all around 70 ohms and 6 by 2 pf caps all with the same colour code but one measured .9 pf. I'm sure that wouldn't do much but I replaced it with a 2pf I had. No different. Oh well! I've got it on marketplace for free and only a few time-wasters have replied. I found the site for that manual and it would be nice to have it. I'm still thinking. I reckon I might have a chance but with my luck it would probably lead me to something I can't replace like a special Kawai IC. I have not quite given up yet. Yes I have checked all connections and buzzed out a lot of wires. The general condition of this piano is really good. I'll bet it's a 5 cent diode somewhere giving me all this grief. I see you are in Florida. I am in Australia. Are there any places in America who might deal in second hand piano PCBs. It seems Pianos are much more popular in USA than here. Marketplace is full of people giving away pianos and pianolas. BTW We have a pianolo, maybe 100 years old which I have got working using a vacuum cleaner motor. Works great but I am the only one who plays it. (when no-one's home-it's too loud) Thanks for your input. Richard
Hi Richard, it sounds like you have been quite busy trying to locate the problem and sometimes it just takes a lot of perseverance to find it. Personally, I wouldn't try to get rid of it yet but would definitely make sure to get the service manual downloaded. From what I can see, using a currency exchange rate app, it would cost around $10AUS plus any bank conversion fee. That would then allow you to confirm that you are getting the correct DC outputs from the PS and check voltage levels at various test points, which often are marked on the PCB's.
The voltage regulators definitely need to be checked as they are known to fail. There should be at least two, one providing a positive voltage and the other a negative, usually the same value which might be anywhere beween 5 and 15 volts. Some keyboards have more than two and again, the service manual circuit diagram can be invaluable here. Your capacitance meter should be handy to check for dodgy capacitors - that's how I found a bad one in my Yamaha organ which lit up okay but produced no sound. I ended up replacing 74 SMD's because when one fails, there is a good chance others will do likewise.
Here's one US company that sells Kawai parts, including PCB's but they are not cheap so might be worth googling for others, perhaps in other countries also. https://instrumentalparts.com/keyboard-parts/kawai-spare-parts/?page=4.
Al
Hello Al, Thanks again. Sorry to dis-appoint but I have promised it to a young fella who is interested in this type of thing and is eager to have a go. He is picking it up tomorrow. I will pass your info onto him and tell him about this forum. I have a few other things on the go so I don't really have much time for this one. Anyway I have learnt a bit about Kawais and how to get them apart is always useful. In future I will look out for free pianos as there is nothing to lose (except petrol). This one cost me about 50 bucks and I am giving it away. Would you believe when I had $5.00 on it I did not get one reply. Made it free and needed a secretary to reply to my messages. (joke). See, there are people tighter than me. Anyway, nice to chat to you and when I get another tricky fault I'll be back on here. All the best. Regards Richard.
Well, that's a good way to part with it and hopefully he'll be able to get it back up and working again. I hope you manage to pick up something else down the road. Unfortunately, my wife has pretty much tied my hands regarding bringing another keyboard back here to fix - we've been married 54 years and she's had enough but I still have a few of them to sell on.
All the best to you too and hopefully, we'll see you back here on the forum with a new project in the near future.
Al