Yamaha PC-100, MP-1

YAMAHA PC-100
Yamaha MP-1

world first key lighting keyboard,
first keyboard with score printer

Yamaha PC-100

This Yamaha instrument from 1982 was likely the world first portable polyphonic keyboard with key lighting feature. Unlike modern such keyboards, not the keys itself but a row of tiny LEDs above the keys flash up to teach keyboard playing. The musics to be learned are stored on so-called PlayCards, those show the musical score and have a strip of magnetic tape on their lower edge that stores the music data, much like nowadays MIDI files.

This is the instrument in its carry case.

To read the data, the card is simply moved by hand from right to left through a slot on the instrument top, which only takes a second (extremely fast in comparison to that time's homecomputer datasette tapes and diskettes). The PlayCard musics are quite complex orchestrated and contain multiple accompaniment voices; thus they were far superior to the barcode reader approach of Casio's competitor MT-70 and resemble rather the quality of Casio's later used ROM- Pack cartridge technology.

The main voice preset sounds are cold and very bright and resemble simple 2 operator FM sounds; interesting is the cheesy "vibraphone" sound which has slow tremolo. The single finger accompaniment has a nice arpeggio. The rhythms employ blip percussion of quite unique electronic style with semi- metallic hissing cymbals (a bit like Casio SK-1) and may be interesting for tekkno. The original German retail price of the PC-100 was 990DM (about 445€). Beside gold metallic also an ultra-rare dark brown woodgrain version was made (seen on eBay).

main features:

44 midsize keys
key lighting with 30 red & yellow LEDs above the main (non chord) keys
slot with a tape head for reading PlayCards
main voice polyphony 8 notes (only 4 with accompaniment)
10 semi- OBS preset sound {organ, trumpet, clarinet, piano, guitar | piccolo, violin, oboe, harpsichord, vibraphone} selected by 5 locking buttons + bank a switch button.
10 semi- OBS preset rhythms {march, waltz, jazz rock, swing, rhumba | disco, slow rock, 16 beat, bossanova, samba} selected by 5 locking buttons + bank a switch button.
locking push button switches to select sounds and rhythms
single finger accompaniment (manual organ chord with rhythm off)
2 switchable accompaniment variations per rhythm
sustain, single finger chord & variation buttons
master volume slider
sliders for auto bass-, arpeggio- and rhythm volume (each 8 steps?)
tempo slider
transpose knob (-5..+6 semitones)
sound generator layers 2 static digital waveforms with independent envelopes, which sounds quite bright and a bit harsh; with low notes sample aliasing gets audible. The trumpet, violin, oboe and piccolo have a delayed vibrato that fades in only after the sustain phase of the envelope begins.
The drums sound like squarewave blips, the hihats sound somewhat metallic and may be shift register noise or a very low- res waveform sample.
multi-chip hardware:

main CPU= "Yamaha YM1032" (40 pin DIL | KAP)
sound IC= "Yamaha YM1019" (40 pin DIL | GE4)
PlayCard CPU= "Yamaha YM1020" (48 pin DIL | IE)
PlayCard amp & obligato filter= "Yamaha IG06110" (16 pin DIL | IEF)
2x SRAM= "TC5514APL-3" (18 pin DIL, 4 bit, in total 4KB)
HF filter= "Yamaha iGO65310" (10 pin SIL | GEF)

jacks for line out, AC adapter and analogue volume pedal

Above the keys are the key lighting LEDs. At the top is the PlayCard slot.

These are the key lighting control buttons. The round knob is for transpose.

This is a PlayCard; much like a MIDI file the data tape strip contains the music data.

notes:

This instrument sounds very bright and almost harsh; thus the "harpsichord" is the most natural sound on it. The PC-100 sounds much like when Yamaha attempted to replicate the at that time modern timbre of their digital FM instruments on cheaper non- FM hardware, thus this keyboard sounds extremely different from the rather muffled analogue timbre of my first PortaSound generation's PS-2. The locking push buttons were likely taken from the previous analogue PortaSounds where their multiple contacts had been technically necessary. A nice sound effect of the PC-100 is the arpeggio, which has a harp- like timbre and is a typical element of early 1980th keyboards; most modern keyboards don't feature this chinking and slightly cheesy accompaniment style anymore. The PC-100 was shipped with these PlayCards.

The "organ" is rather Hammond than church style; it quickly grows slightly duller during its percussive attack phase (likely by crossfading 2 waveforms). The "piano" sounds more like an electric than acoustic one and the bass range strongly resembles a gently picked nylon guitar; "harpsichord" sounds much more realistic. The "trumpet" sounds way too thin and harsh. "trumpet", "violin", and "oboe" have a delayed 7Hz vibrato. "guitar" attempts to be a bright acoustic one. The "vibraphone" has a strong and cheesy sounding 3Hz tremolo, includes sustain and ignores the sustain switch. All other sounds stop almost immediately after key release when sustain is not pressed.

The single finger chord mode employs an envelopeless electronic organ chord timbre, while the automatic accompaniment during rhythm plays a kind of piano chord made from the same waveform with decay envelope, combined with an e-bass. In manual chord mode the variation button toggles between a very bright and a less bright organ timbre or vice versa depending on the selected rhythm. (There are 2 chord timbres in total, those are also used by the accompaniments.)

hardware details

All sounds including percussion are generated digitally by the YM1019 (GE4) sound IC and output through a 10 bit resistor ladder DAC and 3 additional volume control bits to scale the output. The obligato voice however is generated in the PlayCard CPU YM1020 (IE) and filtered in the analogue IC IG06110 (IEF), which also amplifies the tape head signal. The IE also polls PlayCard button group, controls key LEDs and handles song data in SRAM. For this it communicates with the main CPU and sound IC through serial lines. (I haven't examined the hardware, but read the service manual.)

Initially I expected that there was a hidden sequencer easteregg in it, because the hardware used for PlayCard reading and playback (RAM etc.) is technically almost the same like a sequencer. How ever I later found out that keyboard variants with actual sequencer (like Yamaha MP-1) have a different main CPU and especially instead of the PlayCard CPU YM1020 an 80C85A with external ROM, which reduces the chance of its existence. If present, a hidden sequencer feature might even be capable to save data onto PlayCards, which would explain why Yamaha disabled or removed it to prevent users from accidentally overwriting their precious pre- recorded cards (or to avoid disturbing Yamaha's own PlayCard sale interests). At least the KAP serial line /SO1 outputs also 4 unused "sequencer" bits (seen in service manual), which hints that the main CPU can support a sequencer.

The Yamaha ICs mainly communicate through 3 serial data lines /SI1, /SO1, /SO2. According to service manuals, many bits are not digital numbers but flags those (when hi) indicate whether a certain button is pressed or function is active at the moment. So each time slot after the /SY sync signal stands for one function flag or cipher bit. But the KAP sends the note key codes (those differ when transposed) also parallel to the GE4, which may be done to reduce latency. The service manual info looks complete enough to design a MIDI interface using these lines.

caution!: The key matrix and serial data high level is +9V, which can be dangerous to TTL components when shorted for circuit- bending. So always use high resistors during experimentation, followed by 5V zener pulldown diodes against GND to avoid damage.

note: In service manuals Yamaha uses "negative logic" terminology (exchanges the terms "ground" and "supply voltage") and often unintuitive pin function names (like "initial clear" for "reset"). I try to use here standard names and positive logic to avoid confusion.

PlayCard data format

Nowadays PlayCards are not made anymore; it would be interesting to find out the data format to make own PlayCards from MIDI files. Unfortunately Yamaha patented every tiny aspect separately instead of keeping everything in one text. An early key lighting algorithm is in US patent 4378720. The PlayCard system is described in the US patents 4413545 (basic idea) and 5144875 (as key lighting keyboard), the algorithm concept (unfortunately no details) in 4466324 and 4454797. Patent 4387620 reveals that the algorithm uses subroutines for repeatedly played parts of the song to conserve memory. Patent 4587878 describes the chord data. Patent 4406203 hints that data word lengths of musical notes is chosen by use frequency (like ZIP compression), i.e. the file contains a list renumbering all notes instead of using (like ASCII) always the same code for each of them (and every song is transposed to C); this would be surely hard to figure out without patent text. Beside the main voice, PlayCards contain also an additional obligato voice - so the PC-100 plays them often with more complex accompaniment than the normal built-in ones. I guess the very plain hardware of Yamaha PCS-30 is best suited to reverse- engineer the algorithm. Also the Yamaha MK-100 had a sequencer that can save its data on audio cassettes; possibly there are technical similarities in the data format. Has anybody more information on this?

pinout YM1032 (KAP)

The "Yamaha YM1032" (40 pin DIL) is the "KAP" main CPU of the Yamaha PC-100 keyboard (and possibly others). It contains internal ROM with rhythm and accompaniment patterns, polls the keyboard matrix and tempo potentiometer, and controls the external sound IC YM1019 (GE4). (Pinout is based on Yamaha PC-100 service manual.)

pin	name	purpose
1	Vss	supply voltage +9V ?
2	/TL	tempo led out
3	/SY	synchro pulse out (64 clock cycle)
4	/TRCH	truncate signal (from GE4)
5	/IC	reset
6	/KON	key on signal out
7	/N1	note key code out
8	/N2	note key code out
9	/N3	note key code out
10	/N4	note key code out
11	/B1	block key code out
12	/B2	block key code out
13	/B3	block key code out
14	/TCL	tempo voltage in
15	/SO2	serial data (to GE4)
16	/KCI	serial key code in (from IE)
17	/KCO	serial key code out (to IE)
18	C	key matrix out
19	B	key matrix out
20	A#	key matrix out
21	A	key matrix out
22	G#	key matrix out
23	G	key matrix out
24	F#	key matrix out
25	F	key matrix out
26	E	key matrix out
27	D#	key matrix out
28	D	key matrix out
29	C#	key matrix out
30	BL3	note key matrix in (C4#..C5)
31	BL2	note key matrix in (C3#..C4)
32	BL1	note key matrix in (C#2..C3)
33	BL0	note key matrix in (F1..C2)
34	/F1	panel switch matrix in {'Tone', 'Rhythm SW'}
35	/F2	panel switch matrix in {'ABC', 'Rhythm Start', 'Sustain SW'}
36	/F3	panel switch matrix in (transposer)
37	/SO1	serial data in (to GE4)
38	/SI1	serial data in (from IE)
39	VDD	ground (0V)
40	øM	clock in (445KHz)

pinout YM1020 (IE)

The "Yamaha YM1020" (48 pin DIL) is the "IE" PlayCard controller CPU, which was used in 1980th Yamaha keyboards with PlayCard system. It reads PlayCard data from the tape head into external sequencer SRAM, polls the PlayCard button group, controls key lighting LEDs, handles song data in the SRAM. For this it communicates with the main CPU and sound IC through serial lines. It also contains the obligato sound generator. (Pinout is based on Yamaha PC-100 service manual.)

pin	name	purpose
1	Vss	supply voltage +9V
2	/SY	synchro pulse in (64 clock cycle)
3	/TEST	test signal
4	/Si1	serial data 1 in (from KAP)
5	/Si2	serial data 2 in (from GE4)
6	/SO	serial data out (to KAP)
7	/KCi	serial key code in (from KAP)
8	/KCO	serial key code out (to KAP)
9	/MODE	switch data for PlayCard
10	/IC	reset
11	HEAD	magnetic head signal
12	/D0	ram data bus
13	/D1	ram data bus
14	/D2	ram data bus
15	/D3	ram data bus
16	/RW	read/write
17	CS0	ram address bus
18	CS1	ram address bus
19	/A9	ram address bus
20	/A8	ram address bus
21	/A7	ram address bus
22	/A6	ram address bus
23	/A5	ram address bus
24	/A4	ram address bus
25	/A3	ram address bus
26	/A2	ram address bus
27	/A1	ram address bus
28	/A0	ram address bus
29	V	ram supply voltage +5V
30	L11	key led matrix out
31	L22	key led matrix out
32	L33	key led matrix out
33	L44	key led matrix out
34	L55	key led matrix out
35	L1	key led matrix out
36	L2	key led matrix out
37	L3	key led matrix out
38	L4	key led matrix out
39	L5	key led matrix out
40	L6	key led matrix out
41	AV	dac reference voltage
42	AGND	analogue supply voltage (+9V??)
43	OUT1	obligato digital audio out
44	OUT2	obligato digital audio out
45	OUT3	obligato digital audio out
46	OUT4	obligato digital audio out
47	VDD	ground (0V)
48	øM	clock in (445kHz)

pinout YM1019 (GE4)

The "Yamaha YM1019" (40 pin DIL) is the "GE4" sound IC, which was used by Yamaha in many digital pre-FM keyboards of early 1980th. It outputs digital audio through a 10 bit resistor ladder DAC. Like Casio'sHD43517 it uses outside the main waveform 3 additional volume control bits to scale the output. (Casio even patented this as US patent 4414878.) The 8 note polyphonic sound generator layers 2 static digital waveforms with independent envelopes and generates blip percussion. It also polls the control voltages of channel volume potentiometers (rhythm, chord, arpeggio) and is designed to be controlled by a Yamaha "KAP" CPU (or variant like KAP2). The protocol (in service manual) looks like when preset sounds are selected through only 4 bits, thus they seem to be entirely predefined inside GE4 and can not be edited by synthesis parameters (which would make this chip boring). How ever some unused bits may still contain undocumented features. (Pinout is based on Yamaha PC-100 and MP-1 service manuals.)

pin	name	purpose
1	Vss	supply voltage +9V
2	/SY	synchro pulse in (64 clock cycle)
3	/SI1	serial data 1 in (from KAP)
4	/SI2	serial data 2 in (from KAP)
5	/SO2	serial data out (to IE, buffered signal from /SI2?)
6	RHV	rhythm volume voltage in
7	ARV	arpeggio volume voltage in
8	ABV	chord volume voltage in
9	Vref	ADC reference voltage (+2.5V)
10	AGND	analogue supply voltage +9V
11	IC in	reset
12	/IC out	reset out
13	NC	-
14	S3	digital audio out (DAC volume)
15	S2	digital audio out (DAC volume)
16	S1	digital audio out (DAC volume)
17	M9	digital audio out
18	M8	digital audio out
19	M7	digital audio out
20	M6	digital audio out
21	M5	digital audio out
22	M4	digital audio out
23	M3	digital audio out
24	M2	digital audio out
25	M1	digital audio out
26	M0	digital audio out
27	/B3	block key code (from KAP)
28	/B2	block key code (from KAP)
29	/B1	block key code (from KAP)
30	/N4	note key code (from KAP)
31	/N3	note key code (from KAP)
32	/N2	note key code (from KAP)
33	/N1	note key code (from KAP)
34	/KON	note key code (from KAP)
35	/TRCH	truncate signal (to KAP)
36	NC	-
37	NC	-
38	NC	-
39	VDD	ground 0V
40	øM	clock in (445kHz)

pinout iGO6110 (IEF)

The "Yamaha iGO6110" (16 pin DIL) is the "IEF" PlayCard helper IC of Yamaha PC-100. It contains the analogue filter for the obligato voice and the preamp for the tape head signal. (Pinout is based on Yamaha PC-100 and MP-1 service manuals.)

pin	name	purpose
1	MHO	magnetic head out
2	Vref	supply voltage out Vin/2
3	MH1	magnetic head in
4	MH2	magnetic head in
5	GND	IC supply voltage ?
6	Vin	supply voltage
7	+V	IC supply voltage ?
8	MI	mixing in 1
9	F	gain adjust
10	M2	mixing in 2
11	MO	mixing out
12	AI3	obligato in
13	AI2	obligato in
14	AO	obligato audio out
15	AI4	obligato in
16	AI1	obligato in

pinout iGO65310 (GEF)

This is simply an analogue low-pass filter IC, used to remove HF ripple behind the DAC.

pin	function
1	1st stage filter signal in
2	1st stage filter signal in
3	1st stage filter signal out
4	ground 0V
5	bias power out
6	supply voltage +9V
7	supply voltage +9V
8	2nd stage filter signal out
9	2nd stage filter signal in
10	2nd stage filter signal in

A white PC-100 variant with slide switches instead of push buttons was later released as Yamaha PC-50 (seen on eBay). 2 variants without PlayCard reader (and no key lighting) were made as Yamaha PS-400 and PS-300 (I read the manual). The black PS-400 had a chord sequencer, 4-bar rhythm variation switch and duet mode. The beige PS-300 (with beige carry case) has far less features; it has only 37 keys and 8 preset sounds and is missing many features like the chord sequencer, chord variation, transposer knob, duet mode and even lacks the arpeggio. (The Yamaha PS-500 looks identical and Yamaha PSS-401 seems to be a golden 44 keys variant of it.) These instruments were likely intended as digital successors of the analogue Yamaha PS-2 and PS-3. Also the Yamaha PS-200 from 1984 seems to be a black PS-300 variant with slide switches instead of push buttons and 3 built-in demo melodies. A very rare fullsize keyboard with PlayCard system was released in 1983 as Yamaha PC-1000 (49 keys, metallic with dark control panel, case style like Yamaha PS-55 but only 1 speaker | I own one.). Its main voice resembles Yamaha MK-100, while the percussion employs medium resolution samples similar like Casio SK-8. In 1984 the larger PlayCard keyboard Yamaha PCS-500 was released as successor of the PC-100; it featured 49 midsize keys, stereo symphonic (rotary speaker simulation), fingered chord and warmer sound, but unfortunately has no arpeggio anymore. A small PlayCard keyboard with only 32 keys and squarewave sound was released as Yamaha PCS-30. Later Yamaha released some ROM based key lighting instruments like e.g. the small TYU-30.

A PC-100 without keys came out as the "Synthesizer Card Player" Sanyo DP10, which was likely meant as a karaoke-like sing-along device with 2x microphone + aux jack and echo circuit. Although Sanyo omitted the preset sound switches and renamed some controls (e.g. "tone" for "transposer"), it has the same rhythm button set and also the sound (seen on YouTube) is blatantly similar. The DP10 was solely a music player for PlayCards without any means (no midi) to create own contents.

Yamaha MP-1

This keyboard was a close variant of the Yamaha PC-100, but instead of the PlayCard key lighting feature it had as the world only such midsize keyboard a built-in musical score printer.

This printer is a small plotter that draws music notes on a narrow paper strip using a small ball pen. It either prints immediately all played notes, or prints the recorded contents of an internal sequencer. There is also an additional duet mode and much like Yamaha PS-30 it has a stupid "4 bar" button switch that automatically inserts a rhythm fill-in every 4th bar; a manual fill-in button would have been much more useful here. Due to the strong similarity I only mention the differences to the PC-100 here.

different main features:

neither PlayCard slot nor key lighting
built-in musical score printer (draws notes on narrow paper strip using a small ball pen)
button for automatic 4 bar fill-in
duet mode
sequencer (polyphonic)
tuning trimmer
complex multi-chip hardware:

main CPU= "Yamaha YM1034" (64 pin DIL | KAP2)
sound IC= "Yamaha YM1019" (40 pin DIL | GE4)
sequencer CPU= "OKI MSM80C85A, 2902" (44 pin SMD)
plotter MPU= "Hitachi HD44820A71, 2G3 5" (54 pin SMD | DLG1103)
sequencer ROM= "TMM23256P" (28 pin DIL, 32KB | IG078010)
3x SRAM= "Toshiba TC5516AFL" (24 pin SMD, in total 6KB)
HF filter= "Yamaha iGO65310" (10 pin SIL | GEF)

The PCB has a grid of empty test solder pads.

notes:

My MP-1 specimen is missing the plotter pen, thus I could not test the plotter yet, but the plot head seems to move correctly. The big main PCB is fairly crowded. Interesting is that Yamaha introduced in this hardware class already in 1982 digital mixing of rhythm, accompaniment, arpeggio and main voice, while Casio used analogue mixing until late 1980th (abandoned with Casio MT-540); despite the separate volume sliders are potentiometers, they are polled digitally with each only 8 steps. The instrument even assigns polyphony channels of muted parts to the main voice when a slider is set to zero.

hardware details

Although the MP-1 strongly resembles the Yamaha PC-100, it has a physically bigger main CPU YM1034 (KAP2) and instead of the YM1020 (IE) it has a sequencer based on a standard SMD CPU 80C85A with separate 32KB ROM and 6KB SRAM. The plotter is controlled by the MPU Hitachi HD44820A71 (named "DLG1103" in service manual) that communicates with the sequencer CPU. HD44820 is a known part, but with special ROM contents.

Quite similar hardware was used in the Yamaha PS-400, but it has no plotter and MPU, no RAM and a different sequencer CPU "TMP80C39P-6" (40 pin DIL, romless Intel MCS-48 variant with 128 bytes RAM) using the 4KB external ROM "TMM2332P" (24 pin DIL, part no. iG078500 | seen in PS-400 service manual). The score printer algorithm is described in the US patent 4485716.

I haven't analyzed this hardware by myself, but Scott Nordlund made a great hardware analysis of it. This is what he wrote (slightly edited by me):

"I just got an MP-1 a few days ago (serial number 017836) and I spent some time checking it out. Hope you find this interesting:
chips:
solder side (surface mount):

Oki MSM80C85A: 8-bit CPU, not sure if models like the PS-400 have this or if the YM1034 can handle all those duties, maybe this CPU is just for sequencer? Also, there isn't a ROM chip, the IG07806 might include this.

Toshiba TC5516AFL (x3): 2048 byte SRAM (6KByte total), probably works as printer buffer and sequence memory (might be good for circuit-bending)

Hitachi HD44820A71: 4-bit microcomputer with built-in ROM, used here to control the printer

component side:

4558DV: dual op amp

4560D: op amp

TL061CP: op amp

LA4138: audio amplifier

M5232L: voltage detector alarm (low voltage shut-off?)

LB1257: 8-channel driver, for printer

4066BP: quad analog switch (audio processing)

4051BP: 8-channel analog multiplexer (audio processing)

4069UBP: hex inverter

50H000P (x2): inverting hex level translator (to drive the DAC)

40H174P (x2): hex D-type flip-flop

40H074P: dual D-type flip-flop

40H368P (x2): inverting buffer

40H373: octal D-type latch

40H139: 4-line demultiplexer

40H032: quad 2-input OR

40H000: quad 2-input NAND

40H374: octal D-type flip-flop

YM1034: key/button scanning, controls tone generator

YM1019: tone generator

IG07806: likely some kind of interface to the RAM, and/or program ROM for the 80C85 ???

strange integrated components: SI4Z205IN, and one other I can't see, maybe these work as filters

The DAC is basically just a resistor network, 10-bit I think, I don't know the sample rate. There are some additional chips that I guess act as sample and hold (4051 and 4066), etc. which is apparently more sophisticated than the DAC configuration that Casio used at the time. All audio is digitally generated and mixed (main tone, chords, bass, arpeggio, and drums), and output as a single channel, no filters or anything like Casios had, no multiplexing or anything (this is strange- most other keyboards I've seen feature at least some analog mixing for different parts, like the PSS-130, PSS-570, VSS-200, etc., and this was in 1982! Anyway I had hoped I could add separate outputs for different sounds, oh well..).
Of course there are sliders for individual volumes, but this doesn't work the way you'd think. The YM1019 sends out a reference voltage that feeds the potentiometers, the control voltages from these are read by different pins of the YM1019 (not multiplexed and scanned like the key matrix). I had noticed that sounds mute completely when turned to the lowest level, this even intelligently assigns voices- when the arpeggio is on, the upper keyboard part is 3-note polyphonic. When it's turned low enough, it turns off completely and you now have 4-note polyphony. I also noticed that the chord/arpeggio/rhythm volume sliders only work in 8 steps. I'm happy anyway that the final volume control is analog.
I messed around with the button scanning matrix and didn't find any eastereggs, though I may not have been looking in the right places. Unlike most keyboards, it's a bit more difficult to find the matrix lines because it's all on one board, no multiple boards with ribbon connectors like I'm used to seeing.
I don't have a working oscilloscope so testing some of this stuff was a bit difficult. And of course I couldn't view waveforms directly. It would be worth looking at the audio output to see what the waveforms look like, but I haven't done this yet. By simultaneously touching the audio amplifier pins and the printer pins, you can hear the printer signals- pretty cool. Also I noticed that if you similarly "listen" to the RAM chips, the sound varies with the tempo setting. I also noticed that the keys/buttons are polled at a fairly high rate. And of course by individually mixing the bits off of the DAC, the sound can become very distorted.
Drum sounds change pitch along with the voices. I think it's strange how much the drum sounds here resemble FM drums from the OPL2 chip, etc. I'm sure these older keyboards don't use FM, but I suspect maybe Yamaha used some of their existing technology for primitive digital drums, or maybe they deliberately emulated the sounds for the FM chips (I doubt it)."

I later found the service manual to identify the main ICs. I see no IG07806 anywhere. There is only an address latch (IGO78600 = TC40H373P) between sequencer CPU and RAM/ ROM.

pinout YM1034 (KAP2)

The "Yamaha YM1034" (64 pin DIL) is the "KAP2" main CPU of the Yamaha MP-1 and PS-400 keyboard (and possibly others). It contains internal ROM with rhythm and accompaniment patterns, polls the keyboard matrix and tempo potentiometer, and controls the external sound IC YM1019 (GE4). (Pinout is based on Yamaha MP-1and PS-400 service manuals.)

pin	name	purpose
1	Vss	supply voltage +9V
2	/RD	read in from CPU
3	/WR	write in from CPU
4	/TESTB	test pin
5	IRQ	interrupt out
6	N.C.	-
7	CSL	chip select low
8	CSH	chip select high
9	IQ/M	interrupt out
10	-5V	supply voltage -5V (?)
11	/SY	synchro pulse out (to GE4)
12	/TRCH	truncate signal (from GE4)
13	/IC	reset
14	N.C.	-
15	N.C.	-
16	/TL	tempo led out
17	Vss	supply voltage +9V
18	/KON	key ON signal out
19	/N1	note key data out
20	/N2	note key data out
21	/N3	note key data out
22	/N4	note key data out
23	/B1	block key data out
24	/B2	block key data out
25	/B3	block key data out
26	TCL	tempo voltage in
27	/SO2	serial data out (to GE4)
28	/KCI	key code in
29	/TESTA	test pin
30	/KCO	key code out
31	C	key matrix out
32	B	key matrix out

pin	name	purpose
33	N.C.	-
34	A#	key matrix out
35	A	key matrix out
36	G#	key matrix out
37	G	key matrix out
38	F#	key matrix out
39	F	key matrix out
40	E	key matrix out
41	D#	key matrix out
42	D	key matrix out
43	C#	key matrix out
44	BL3	note key matrix in (C4#..C5)
45	BL2	note key matrix in (C3#..C4)
46	BL1	note key matrix in (C#2..C3)
47	BL0	note key matrix in (F1..C2)
48	N.C.	-
49	/F1	panel switch matrix in {'Tone', 'Rhythm SW'}
50	/F2	panel switch matrix in {'ABC', 'Rhythm Start', 'Sustain SW'}
51	/F3	panel switch matrix in (transposer)
52	/F4	panel switch matrix in {'Melody', 'Chord', 'Printer SW'}
53	/SO1	serial data out (to GE4)
54	/SI1	serial data in (from GE4)
55	DB0	ram data bus
56	DB1	ram data bus
57	DB2	ram data bus
58	DB3	ram data bus
59	DB4	ram data bus
60	DB5	ram data bus
61	DB6	ram data bus
62	DB7	ram data bus
63	VDD	supply voltage 0V
64	øM	clock in (446kHz)

The KAP2 is a close relative of the PC-100 KAP CPU with additional pins.

Question: Can anybody tell me what the original plotter ball pen for Yamaha MP-1 looks like? I want to replicate one.

With my Yamaha MP-1 someone had stuffed a cylindrical lump of tar-like dirt into the tuning trimmer hole. I first thought it was the remain of the plotter pen, but according to the instruction sticker on the plotter lid a ball pen was used for it. Someone e-mailed me that also his Yamaha PC-100 had the same sticky stick in its trimmer hole, and after a close look even at my PC-100 trimmer hole I discovered some black smeary stains from it. Thus it was apparently originally placed there by the manufacturer and not just stuffed in by a kid - likely some kind of plug that was originally made of a wrongly mixed or accidentally unvulcanized rubber compound that turned into pulp after few years. I only know that my Yamaha PS-20 and PS-30 had badly smearing dissolved black foam rubber pods at their case bottom. However I don't understand why anybody should plug a trimmer hole tight with a soft material at all. It might be that the case was painted after assembly (which makes very little sense) and the soft plug though should protect the electronics against paint, and the manufacturer forgot to remove it. Someone e-mailed me that his MP-1 also had this tar lump.

*removal of these screws voids warranty...*

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