Yamaha Electric Piano CLP550 no keyboard output

[dkneyle]

Re: Yamaha Electric Piano CLP550 no keyboard output

why the u.k.?
i'm sure there are much closer suppliers of decent sockets.
where did you order & what did you pay?

I live in a regional area without ready access to electronic part suppliers. The main industry suppliers of electronc parts to the repair industry want to charge big money for post and delivery (they are geared up for large scale orders - not the hobby repairer). I find that ordering from offshore suppliers is usually a fraction of the cost for just a few more days wait for delivery. In fact, the UK is usually pretty fast - about 5 days. I paid about A$10 for four sockets delivered to my door. I'm happy with that. The seller calls themselves Spiratronics on E-Bay.

Quick queston about those old Static ROMs. The owner said the piano hadn't been played for about a year (my guess is probably longer). If the ROM has had no power for a long period of time is that more likely for it to fail?

[stj]

Re: Yamaha Electric Piano CLP550 no keyboard output

no.
storage temperature may make a difference if it's in freezing conditions maybe.
but roms arent "refreshed" by being powered up.

[dkneyle]

Re: Yamaha Electric Piano CLP550 no keyboard output

UPDATE. I pulled the ROMS from the PCB and installed turned pin sockets. With no ROMS inserted I powered up. All was silent (as I'd hoped). I hit a few keys Some of the lowest keys generated a very quiet 'click' sound. I then inserted IC8 (GenROM1) and powered up. I was met with a cacophony of noises, screetches and the usual weirdness as per previous posts. Maybe I had got it in one? I pull IC8 and inserted IC9 (GenROM2) and had very similar sorts of sounds, but not as intense. Mmmm. I pulled IC9 and put in IC10. Nothing. Quiet and no response to any keys. So I put IC9 and IC8 back in. Powered up: all quiet, no response to keys.
So I'm moving away from the ROMs being the problem. The finger gets pointed more at the sound generator chip IC2. This is a SMD square chip mounted on the reverse side of the board.
Trying to think this through like a detective. The piano was working OK. It isn't touched for 12 months, and when the owner next tries to use it there is nothing. When I begin working on it I notice that I can get these distorted sounds out of it when it starts off from cold and hasn't been touched for some hours. The longer it is left with power the less and less these distorted sounds get.
Clutching at straws, I'm going to hit IC2 with a heat gun and see if I can't re-melt the solder joints.
We are in a coastal environment, this home that it lived in is probably 800 metres from the sea, although in a strong breeze you can smell the salt in the air. However the physical condition of the board appears OK. I looked it over with a mag lens and didn't see anything out of the ordinary.
Any other suggestions are much appreciated.

[dkneyle]

Re: Yamaha Electric Piano CLP550 no keyboard output

I was wondering if the clock for the sound generator was running. It is a 6.4MHz crystal with a 1M ohm resistor across it. I don't own or have access to a scope to see if the clock is running. But I thought I'd just try an experiment and see if my multimeter on AC range would read anything. I was greeted by VERY LOUD screetching sounds. But only if I place my meter across the resistor. A single lead didn't produce this effect. I am wondering if the crystal is defective? If the clock isn't running, or only sometimes runs a bit at weird frequencies, it could explain the lack of output. I thought I'd read somewhere else about crystals failing.
Once again, any input is appreciated.
BTW, I checked the 5 volts at the input to the chip. OK at 5.09, with no AC ripple showing on my multimeter.

[stj]

Re: Yamaha Electric Piano CLP550 no keyboard output

i'm wondering about the chip select on the roms after what yam said.

look at the datasheet.
there are 2 inputs, CE and OE usually.
i suspect one will be connected to ground.
the other will go to a chip that selects each rom.
see if i'm right.
if i am - tell me the number on the chip they connect to - probably something like 74ls138 or 139.
go check.

[dkneyle]

Re: Yamaha Electric Piano CLP550 no keyboard output

OE on two of the ROMs are feed from an Inverter IC. Type TC40H004P.
CE is feed from the sound generator chip.
I'm attaching the circuit diagram.

I've done some investigations on that TC40H004P Hex inverter. Read this forum post from elsewhere: http://electro-music.com/forum/post-119201.html

It would appear that this device has failed in another electronic keyboard, albeit, not the Yamaha CLP-550. But that does seem an interesting coincidence, doesn't it?
Their investigations suggested that 74HC04 should be an equivalent device.

[dkneyle]

Re: Yamaha Electric Piano CLP550 no keyboard output

I also stumbled upon this Forum Thread elsewhere: http://forum.allaboutcircuits.com/sh...ad.php?t=71808

It's for a different Yamaha Electric Piano, but the story sounds all too familiar. It might give me some guidance. Lot's of fault finding involving a scope. I might need to invest in one eventually just to be able to see what's going on with those various address, data and ciontrol lines.

[stj]

Re: Yamaha Electric Piano CLP550 no keyboard output

looked at the schems
i'd try replacing ic11 the 74ls04 or 74hc04 or 74hct04
or whatever it is - it's an 04, but the type isnt marked on the schems
i'd try the hc.

[dkneyle]

Re: Yamaha Electric Piano CLP550 no keyboard output

I have ordered a 74HC04 locally, so hopefully it will be here in a couple of days and I can report back. I've also ordered a socket so I can easily compare old with new.
That Hex Inverter feeds ROMS 1 & 2, but not ROM 3. Interesting that when I was swapping ROMs in and out, ROMs 1 & 2 gave me weird sounds but ROM3 was silent.
BTW, there's a brief parts index hidden away on the righthand side of the circuit diagram.
(If I do ever get this going we'll still be dumping those ROMs. Maybe even if I don't get it going now that we suspect that they are probbaly OK.)

[stj]

Re: Yamaha Electric Piano CLP550 no keyboard output

looking forward to hearing what difference the chip makes.

[dkneyle]

Re: Yamaha Electric Piano CLP550 no keyboard output

Sadly, replacing the HEX inverter has not resolved the situation. Sometimes the keyboard appears to be slightly responsive, producing some sounds, upper keys producing noises with higher tones, lower keys producing louder and lower tone sounds. Still nothing like the expected sounds of a piano. And it's completely inconsistent. I can power up sometimes and it will be completely dead; totally unresponsive to any key strikes. Then I leave it powered up for a few minutes and it starts to respond as I've described. Although sometimes the situation can be completely reversed! Power up, it is somewhat responsive and then it settles back after a few minutes into no response.
I pushed and proded once again around the board. I must say, there is a sense that manipulating the board does somehow change the response.
I'm going to test continuity of all the bus lines and just check that all is good there. This board is double sided and I'm just wondering about the integrity of some of those through-hole connections.
By the way, I used a fine soldering iron tip and re-worked all the pins of the sound generator chip just in case.
I'm close to the point of needing to invest in a CRO to see what is going on.

[stj]

Re: Yamaha Electric Piano CLP550 no keyboard output

if that fails you can send me the roms for dumping.

[dkneyle]

Re: Yamaha Electric Piano CLP550 no keyboard output

Yes, one way or the other we'll get those ROM dumps out! I feel like I want to try to get this going; it's as if I'm missing something easy. The fact that I get these sounds out suggests maybe the sound gen chip is trying to do something. I keep going back to the reported problem. Was working, not touched for 12 months, then no go at power up. That sounds like a 'mechanical' failure to me - open circuit, etc, rather than a semi-conductor failure. In fault finding I've always followed the rule that it's usually a simple explanation rather than a more complex one.

[ogilvie]

Re: Yamaha Electric Piano CLP550 no keyboard output

90% certain it is the DACs Id change them and start worrying if it does not fixit.

[stj]

Re: Yamaha Electric Piano CLP550 no keyboard output

90% certain it is the DACs Id change them and start worrying if it does not fixit.

do you work on these?
if you do, do you archive the roms?

[dkneyle]

Re: Yamaha Electric Piano CLP550 no keyboard output

Thanks for the suggestion ogilvie. I did change over one DAC chip PCM56P that is the final link between the digital and analogue stages and had no success. If you look at Post #46 you can see the circuit. Most of the other chips are proprietary Yamaha specialist chips that even Yamaha no longer sell. I've purchased one of those USB digital oscilloscopes and the digital stages seem to look OK from a superficial check. I thought that maybe the crystal oscillators (clocks) had failed but they appear to be working. If you look at the circuit you might be able to suggest some other possibilities?
STJ: Until this post arrived I'd all but decided to sell parts for scrap. Living in a regional area of Oz makes the shipping costs prohibitive for anyone looking to get it with the hope of repairing it themselves. As I think I've determined, the ROMS are probably OK. In light of this I'd be prepared to post them to you and you can see if you can pull the codes out of them and post it up to the web. If I go down this path I'll PM you and get a delivery address.

[stj]

Re: Yamaha Electric Piano CLP550 no keyboard output

you cant say the roms are o.k. unless you can read them, and know atleast what the checksum should be.
those roms are 4megabit, that's 4,000,000 bits - if just a handfull go bad it wont pass the correct data.

[TabajaraLabs]

Re: Yamaha Electric Piano CLP550 no keyboard output

Any updates in this thread?
Just got a CLP550 with the same problem. I can dump ROMs here. If someone wants to take a look at the code, I can share it.

[stj]

Re: Yamaha Electric Piano CLP550 no keyboard output

dump them - atleast we either get a backup or the programmer tells you there is a stuck bit or address-line.

[dkneyle]

Re: Yamaha Electric Piano CLP550 no keyboard output

I gave up on the beast and have stored it under my house and advertised it for parts on E-Bay. But I'd happily send the ROMs to someone like STJ to see if the code is corrupt or otherwise.
I've seen a working CLP-550 advertised on E-Bay in Sydney for A$300. Hardly worth the worry of trying to repair this old beast if I really wanted to; should just buy this one and swap it for the buggered machine and charge it to the client who asked to see if I could fix the original!
Anyway, if STJ or someone wants those ROMs to at least download the code and make it available up in the cloud for anyone else that wants to burn new chips, than I'll send them overseas to wherever.
In many ways I'd like to find out if it really is the ROMs that are to blame for the failure. I suspect not, but what has failed has got me mystified.