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NEKID PICTURES!! (Yamaha P120) #1439246
05/18/10 06:49 PM
05/18/10 06:49 PM
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Northern NJ
dewster Offline OP
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Photos Of Naked Model On The Internet!

Yesterday I decided to take our Yamaha P120 apart. My interests were two-fold. Mainly, like any engineer worth his salt, I wanted to peer at the guts inside, write down some chip numbers, and look up the parts on the web - level one reverse engineering. But I also wanted to do my part to push any visiting techs over the edge into a nervous breakdown, so I'm sharing some photos of it here in this public forum. smile

I took it off the stand and set it on the studio rug on it's back. The application of one Philips screwdriver over a 10 minute time span and the dirty deed was done. Our Yamaha P120 laid bare before my eyes - make love to the camera, baby!

[Linked Image]
Here is the P120 disassembled. It turns out you really only need to remove the screws to the back section, not the sides or the front. The back section slides into slots in each end piece, to remove it just slide it back and then lift up once you hit the end of the slots. The left end holds all the connectors (a rather awkward and unfortunate design decision IMO). The whole deal is supported by a slab of aluminized MDF on the bottom.

[Linked Image]
A view to the left side of the guts. Here you can see the main processor board and the left speaker. Lots of wires. Must be somewhat labor intensive to manufacture.

[Linked Image]
A view to the right side of the guts. Here you can see the audio amplifier board (nice heatsink) and the right speaker. The speakers are rated 10W / 20W max. and as you can see are unfortunately not acoustically contained in any way, just flopping in the breeze. They actually point out the back of the DP, with a slot in the top permitting the backwave to reach the player. Pretty odd all around. Sounds about as good as you might expect for such an arrangement (i.e. not too good).

[Linked Image]
A better view of the processor board. You can see the wire harness to the keyboard, and a large RF-reducing ferrite doing double duty as a wire anchor. The upper board holds all the control buttons and blinking lights and stuff.

[Linked Image]
Key mechanism in the key-up position. Yamaha uses rods bent in a hairpin shape for the weight. You can kind of see the leaf spring there too.

[Linked Image]
Key mechanism in the key-down position.


On the audio board heatsink I discoved this IC:

LA4705N - 15w 2-channel Power Amplifier

And here are some of the parts on the main board

CY62256LL-70SNC - 256K (32K x 8) Static RAM
OKI MSM514260E-60TK - 256K x 16 DRAM
PCM69AU - Dual D/A, 18-bit
Yamaha X201110 - house numbered, most likely flash
Yamaha X201??D - house numbered, most likely ROM or key scanner
Yamaha ??947C0 - house numbered, most likely ASIC
TD62785F - Transistor array (8x)


I'm kind of surprised they apparently use ASICs as processors, they must make tons of these. Too bad the flash is house numbered, I would have liked to have known the size of the sample storage. Couldn't find any soul to speak of.

Afterward I buttoned it back up and checked all the keys - it seems no worse for the peek at the internal organs.

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Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439304
05/18/10 08:19 PM
05/18/10 08:19 PM
Joined: Jan 2010
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Germany
hpeterh Offline
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The keyboard looks mostly the same as the GHE/GHD in my CVP96.
The keyscanner is a single prozessor chip 40 pin DIL and is on the PCB that is beneath the keys. (when it is the same as I had seen)
If I counted correctly, there are 8 wires. Thats not enough for VCC,GND and 88*2 switches to decode, so it is probably the same ;-).


Did you check if the hammers can move independently from the keys? (I dont believe so)

For further questions ask here for the service manual.
http://www.wdgreenhill.com/

They have much more than listed, ask.
You get legal paperware only, no pdf's.

;-)

Peter



Last edited by hpeterh; 05/18/10 08:37 PM.

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Re: NEKID PICTURES!! (Yamaha P120) [Re: hpeterh] #1439333
05/18/10 09:10 PM
05/18/10 09:10 PM
Joined: Jul 2005
Posts: 1,323
Canada
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Melodialworks Music Offline
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Thanks, Dewster. Nice photos. Always interesting to see the inside of these machines . . .

Re: NEKID PICTURES!! (Yamaha P120) [Re: hpeterh] #1439339
05/18/10 09:18 PM
05/18/10 09:18 PM
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Redondo Beach, California
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ChrisA Offline
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Originally Posted by hpeterh

If I counted correctly, there are 8 wires. Thats not enough for VCC,GND and 88*2 switches to decode, so it is probably the same ;-).



They don't need to monitor all the keys at once. They scan the keys. Basically they ask each key switch in turn "are you closed?" Then the switch can report it's state using a "party line" shared by all the 88*2 switches.

Re: NEKID PICTURES!! (Yamaha P120) [Re: Melodialworks Music] #1439341
05/18/10 09:21 PM
05/18/10 09:21 PM
Joined: Sep 2007
Posts: 15,111
Hamamatsu, Japan
Kawai James Offline
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Agreed - thanks for the pics dewster.

Do you know approximately when this instrument was manufactured? It would be interesting to compare the internals to the P140 which I believe replaced the P120, then the P155 which replaced that.

Hmmm...I wonder why Yamaha chose to name the product P155 - P160 would surely have been the more logical progression, albeit potentially confusing with the YDP-160.

Cheers,
James
x


Employed by Kawai Japan, however the opinions I express are my own.
Nord Electro 3 & occasional rare groove player.

"I agree that the User Manual is very good." - arc7urus, March 2019
Re: NEKID PICTURES!! (Yamaha P120) [Re: Kawai James] #1439344
05/18/10 09:26 PM
05/18/10 09:26 PM
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Posts: 1,323
Canada
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Melodialworks Music Offline
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I've never really understood the numbering of various models of various manufacturers. I suspect that they've got a bunch of number and letter combinations on a giant dartboard. When it comes time for a new model, they throw a dart.

Re: NEKID PICTURES!! (Yamaha P120) [Re: hpeterh] #1439386
05/18/10 10:43 PM
05/18/10 10:43 PM
Joined: Dec 2009
Posts: 4,675
Northern NJ
dewster Offline OP
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Originally Posted by hpeterh
The keyboard looks mostly the same as the GHE/GHD in my CVP96.
The keyscanner is a single prozessor chip 40 pin DIL and is on the PCB that is beneath the keys. (when it is the same as I had seen)
If I counted correctly, there are 8 wires. Thats not enough for VCC,GND and 88*2 switches to decode, so it is probably the same ;-).

Good eye! Yes that's 8 wires going to the keyboard assembly. I believe the key scanner chip is a 48 pin DIP right there on the main board (interesting that it is socketed):

[Linked Image]

Maybe they use diodes and multiplex the heck out of it? Or perhaps there is a scanner on the key assembly and it sends serial (MIDI?) data? I should have investigated that more closely.

I didn't think to check the mechanical independence of the hammers, though I did take a movie of pressing a key, see what you think:

http://www.mediafire.com/?enjlzmowwz2

Thanks for the link!

Re: NEKID PICTURES!! (Yamaha P120) [Re: Kawai James] #1439390
05/18/10 10:47 PM
05/18/10 10:47 PM
Joined: Dec 2009
Posts: 4,675
Northern NJ
dewster Offline OP
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Originally Posted by Kawai James
Do you know approximately when this instrument was manufactured?

There's a chip in there with 2001 marked on it if that means anything. Perhaps the serial number has the date encrypted in it somehow, or there is a table of what serials were manufactured when somewhere?

Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439440
05/19/10 01:28 AM
05/19/10 01:28 AM
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Fantastic breakdown of the keyboard dewster!

Originally Posted by dewster

I'm kind of surprised they apparently use ASICs as processors, they must make tons of these. Too bad the flash is house numbered, I would have liked to have known the size of the sample storage. Couldn't find any soul to speak of.


It doesn't surprise me that an instrument of this vintage has an ASIC. My guess is that there's probably a fair amount of full custom DSP to provide all the goodies including real-time effects with low latencies. They weren't going to use FPGAs of that era (nowhere near dense enough for the cost), and off-the-shelf DSPs were powerful enough but probably more expensive per unit than the ASIC (even considering ASIC NRE) and possibly more hungry for both board space and power. That's not including other things like the main micro, peripheral interfaces, etc. which they could do with an ASIC. Off-the-shelf System-on-a-Chip was still getting its legs at this point and was definitely not targeting this application.

Once again, hat's off to you for a great review!


RD-700GX + SN Piano Expansion
If you're playing and you know it, wash your hands! If you're playing and you know it, no sanitizer!
If you're playing and you know it, and don't want your keys to show it,
If you're playing and you know it, clip your nails!
Re: NEKID PICTURES!! (Yamaha P120) [Re: pianodilemma] #1439480
05/19/10 03:11 AM
05/19/10 03:11 AM
Joined: Jul 2009
Posts: 983
Earth
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The P-120 wasn't one of Yamaha's better moments...you'd be better off trading it in on a Roland RD-700 GXF...they look much nicer when taken apart...

Snazzy


Semper Gumby: Always flexible \:^)
Re: NEKID PICTURES!! (Yamaha P120) [Re: snazzyplayer] #1439485
05/19/10 03:25 AM
05/19/10 03:25 AM
Joined: Sep 2007
Posts: 15,111
Hamamatsu, Japan
Kawai James Offline
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Quote
The P-120 wasn't one of Yamaha's better moments.


Snazzy, would you care to elaborate?

Cheers,
James
x


Employed by Kawai Japan, however the opinions I express are my own.
Nord Electro 3 & occasional rare groove player.

"I agree that the User Manual is very good." - arc7urus, March 2019
Re: NEKID PICTURES!! (Yamaha P120) [Re: Kawai James] #1439502
05/19/10 04:47 AM
05/19/10 04:47 AM
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Posts: 983
Earth
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No need...Dewster is doing fine.

Snazzy


Semper Gumby: Always flexible \:^)
Re: NEKID PICTURES!! (Yamaha P120) [Re: snazzyplayer] #1439504
05/19/10 04:53 AM
05/19/10 04:53 AM
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theJourney Offline
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What have been the highest selling Yamaha boards in the past? Anyone know the numbers?

Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439510
05/19/10 05:28 AM
05/19/10 05:28 AM
Joined: Jan 2010
Posts: 824
Germany
hpeterh Offline
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[Linked Image]

This one of the two keyboard - contact PCB's taken from CVP96 SM.
Because it has a quartz, it is probably a single chip CPU that actively scans and debounces the contacts and initiates interrupts and sends serial data to the main CPU.

I think this 40Pin DIL visible on your photos scans and multiplexes the front panel switches and LED's.

Last edited by hpeterh; 05/19/10 06:34 AM.

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Re: NEKID PICTURES!! (Yamaha P120) [Re: theJourney] #1439511
05/19/10 05:28 AM
05/19/10 05:28 AM
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Earth
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Originally Posted by theJourney
What have been the highest selling Yamaha boards in the past? Anyone know the numbers?


Yamaha's DX7 keyboard synthesizer reportedly sold 160,000 during the 80's, according to Keyfax 4.

Korgs's M1 has allegedly surpassed this figure (Keyfax 4 again).

Best selling piano was supposedly the P-250 (2002) from what I hear.

Snazzy


Semper Gumby: Always flexible \:^)
Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439689
05/19/10 11:58 AM
05/19/10 11:58 AM
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Originally Posted by dewster
... The speakers are rated 10W / 20W max. and as you can see are unfortunately not acoustically contained in any way, just flopping in the breeze. They actually point out the back of the DP, with a slot in the top permitting the backwave to reach the player. Pretty odd all around.


I think their design is more sophisticated than you give credit. I think they assume the piano will be placed up against a wall. They are using the wall, the internal volume of the P120 case and the slotted opening to shape the sound. They do a good job considering the very low cost parts used. It actually would have been easier for them to mount the speaker cones facing up and cut a speaker grill in thetop of the piano case. But then it would really sound like a toy piano.

There is enough room inside for you to "hot rod" the audio section maybe with some full range Fostex drivers and a better amp.

Re: NEKID PICTURES!! (Yamaha P120) [Re: ChrisA] #1439791
05/19/10 03:03 PM
05/19/10 03:03 PM
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dewster Offline OP
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Originally Posted by ChrisA
They are using the wall, the internal volume of the P120 case and the slotted opening to shape the sound. They do a good job considering the very low cost parts used.

I've seen some pretty amazing stuff done with low cost parts. A decently flat mid-bass driver, a paper cone tweeter, an electrolytic non-polar capacitor, maybe a sandblock resistor, and a coil if absolutely necessary, all can be had for $10 to $15 per side retail. Put that in a proper sealed or ported enclosure and it can sound like way more than you paid for. But here all they have is an oval speaker, and they point the back of it at you through a slot in a big leaky box. They're not even trying.

Originally Posted by ChrisA
It actually would have been easier for them to mount the speaker cones facing up and cut a speaker grill in thetop of the piano case. But then it would really sound like a toy piano.

The flattest FR is almost always from the front of the driver on-axis. The backs of these speakers point into the entire cavity of the DP, which isn't sealed by any means. The L & R speakers even share the same acoustic space. In this leaky space the slot can't have any real tuning capability as in a ported enclosure. In such a scenario the main thing the backwave emerging from the slot would do is cancel out the frontwave, producing anemic bass. It's pretty clear Thiele & Small weren't consulted for this design.

Originally Posted by ChrisA
There is enough room inside for you to "hot rod" the audio section maybe with some full range Fostex drivers and a better amp.

It really could use a better set of sounds too, so beefing up the audio would be a diminishing returns thing. Easier just to buy something new with no built-in speakers as we're already using an external amp.

Re: NEKID PICTURES!! (Yamaha P120) [Re: dewster] #1439801
05/19/10 03:21 PM
05/19/10 03:21 PM
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fascinating stuff... except i won't take my p155 apart.

Re: NEKID PICTURES!! (Yamaha P120) [Re: signa] #1439805
05/19/10 03:30 PM
05/19/10 03:30 PM
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Lexington, Kentucky
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<--- is hyperventilating.

This is my favorite thread for all week. laugh Loved the pics, and the commentary just as much. "make love to the camera, baby" [snorts with laughter]

Re: NEKID PICTURES!! (Yamaha P120) [Re: hpeterh] #1439817
05/19/10 03:49 PM
05/19/10 03:49 PM
Joined: Dec 2009
Posts: 4,675
Northern NJ
dewster Offline OP
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Originally Posted by hpeterh
[Linked Image]

Interesting. They have 15 banks of 12, which gives 15 * 12 = 180.

180 / 88 = 2.0455

So there are two switch contacts per key, correct?

The XCK / ACK looks like some kind of handshake, S0 could be serial out. Series resistors on the outputs for signal integrity. And I agree that the crystal strongly implies a processor, particularly that humongous DIP.

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