CASIO PT-88, 100 sound ToneBank mini keyboard with ROM-Pack ? key lighting

This is basically a Casio SA-1 with ROM-Pack slot and melody guide key lighting feature (LED row above the keys).

Additionally it has 5 drum/ effect pads and 4 demos, but unfortunately the rhythm set is much simpler than on SA-1 and features only 12 preset rhythms without accompaniment. Due to the many similarity with Casio SA-1 I only describe here the differences.

different main features:

eastereggs:

  • 3 drumpads addable (no new sounds).
  • different melody guide (without waiting) addable.
  • polyphony 6 notes addable (needs key diodes against note mess).

    • notes:

    Unlike older Casio key lighting keyboards the melody guide feature is much restricted; the LEDs are always on and it always waits until a key is pressed; in "any key play" mode any key steps through the melody, in "music guide" mode it waits until the correct key is pressed (wrong notes sound also). The rhythms are made from simple medium resolution acoustic drum kit samples and include no accompaniment (ROM-Pack musics use additional synth toms and fill-ins). The drumpads can be switched between effect- and drum kit sounds; their sound set corresponds to the fullsize Casio CT-840. The volume is here controlled through a mechanical 5 step slide switch, which prevents using the tempo change easteregg of Casio SA-1. As usual, the ROM-Pack melodies are selected through the keys; when no ROM-Pack cartridge is inserted, the instrument uses 4 internal demo songs on the first 4 white keys instead.
     

    hardware details

    The Casio PT-88 is based on the OKI M6521-02 CPU. This hardware strongly resembles classic SA-series but supports ROM-Pack and key lighting.
     

    keyboard matrix

    The key matrix is grouped by 8, while most bigger Casios have 6er groups. It supports 3 additional drumpads, a melody guide mode without waiting and can enable higher polyphony.

    This matrix was analyzed by myself and verified with service manuals of Casio ML-2, ML-3, ML-1.
     
    31 KI0
     32 KI1
     33 KI2
    34 KI3
    35 KI4
    36 KI5
    37 KI6
    38 KI7
     
    CPU pin
    in 0
    in 1
    in 2
    in 3
    in 4
    in 5
    in 6
    in 7
    in / out
     
    o
    F3
    o
    F#3
    o
    G3
    o
    G#3
    o
    A3
    o
    A#3
    o
    B3
    o
    C4
    out 0
    39 KO0
    o
    C#4
    o
    D4
    o
    D#4
    o
    E4
    o
    F4
    o
    F#4
    o
    G4
    o
    G#4
    out 1
    40 KO1
    o
    A4
    o
    A#4
    o
    B4
    o
    C5
    o
    C#5
    o
    D5
    o
    D#5
    o
    E5
    out 2
    41 KO2
    o
    F5
    o
    F#5
    o
    G5
    o
    G#5
    o
    A5
    o
    A#5
    o
    B5
    o
    C6
    out 3
    42 KO3
    P.
    1 (hi synth tom)
    P.
    2 (siren up)
    P.
    3 (bird)
    P.
    4 (phone bell)
    P.
    5 (laser beam)
    P.
    6 (snare)
    P.
    7 (cymbal)
    P.
    8 (lo synth tom)
    out 4
    43 KO4
    N.
    '0'
    N.
    '1'
    N.
    '2'
    N.
    '3'
    N.
    '4'
    stop
    tempo
    -
    stop
    out 5
    44 KO5
    N.
    '5'
    N.
    '6'
    N.
    '7'
    N.
    '8'
    N.
    '9'
    P.
    variation
    R.
    select
    tempo
    +
    out 6
    45 KO6
    M.
    melody guide
    M.
    melody guide 2
    M.
    melody guide 2
    M.
    melody guide
    M.
    any key
    M.
    auto play
    M.
    play
    polyphony 6
    [diode]
    out 7
    46 KO7

    The input lines are active- high, i.e. react on +Vs, thus any functions are triggered by a switch in series to a diode from one "out" to one "in" pin.
     

    legend:
    "o"
    		 = keyboard key
    R.
    		 = rhythm
    N.
    		 = number entry (cipher buttons)
    P.
    		 = drum-/effect pad
    M.
    		 = mode select switch
    orange
    background     		 = easteregg (unconnected feature)
    grey 
    background    		 = unconnected doublet

    In the LED matrix each LED is wired from an LY# to an LX# pin of the CPU.

    eastereggs

    3 additional drumpad buttons at KO4->KI5..KI7 play snare, cymbal and low synth tom. In PT-88 these are anyway reachable through the pad variation button and nothing special. Strange is that the variation button plays on these pads 3 of the preset sounds (which resembles SK-series behaviour when no sample is recorded).

    The "melody guide 2" mode at KO7->KI2 works like the normal one, but the song does not wait until you play the correct note. Like karaoke it just plays the accompaniment of the song and the LEDs suggest what you should play, but it doesn't care if you don't.

    upgrade polyphony:

    Like M6387 (classic SA-series) also M6521 based hardware can run in reduced polyphony mode, because in cheapened models key matrix diodes were omitted and the polyphony limited to 2 to prevent note mess. Connecting a diode at KO7->KI7 (sensed during power-on) enables 6-note polyphony mode. But to make it work properly, you will need to additionally solder 1 diode in series with each key. For technical details see here.

    pinout M6521

    The "OKI M6521-xx" CPU (pins count anticlockwise, xx = software number of internal ROM) is a 60 pin SMD variant of the M6387 that (unlike older Casio keyboards) supports a matrix of key lighting LEDs without the need of driver transistors. Each LED is wired from an LY to an LX pin. The pins 51..58 can control the ROM-Pack port. Without a ROM-Pack connected, the key lighting uses demo songs from its internal ROM. Polyphony is up to 6 notes. Like M6387 it is clocked at 21.725 MHz.

    The versions of "OKI M6521-xx" ("xx" = software number of internal ROM) differ in demo songs, rhythms and sound set.
     
    software number hardware class notes & features
    02 PT-88 32 keys, key lighting, 100 sounds, 12 rhythms, 5 drumpads, rom-pack, 4 songs
    04 KS-02 8 OBS sound buttons, 12 rhythms, rom-pack, 6 songs
    06 RAP-1 25 sounds, 30 rhythms implemented as songs
    08 RAP-10 no keyboard, 10 rhythms implemented as songs
    09 DJ-1 like 06, some changed sounds, different rhythms
    10 ML-1 25 sounds, 12 rhythms, 10 songs (need no lit sharp keys)
    11 ML-2 like 11 with changed 10 songs
    12 ? *)
    13 ML-3 bugfixed 10?
    *) mentioned on chip vendor websites.

    This pinout was concluded from the service manual of ML-2 (which uses no ROM-Pack), SK-8 service manual and wiring of the PT-88 PCB.
     
    pin name purpose
    1 LY1 led matrix out
    2 LY2 led matrix out
    3 LY3 led matrix out
    4 LY4 led matrix out
    5 LY5 led matrix out
    6 LY6 led matrix out
    7 LY7 led matrix out
    8 LVDD1 led supply voltage +5V
    9 LGND2 led ground
    10 LX0 supply voltage +5V
    11 LX1 led matrix out
    12 LX2 led matrix out
    13 LX3 led matrix out
    14 LX4 led matrix out (ML-2: not used)
    15 LX5 led matrix out (ML-2: not used)
    16 LX6 led matrix out (ML-2: not used)
    17 LX7 led matrix out (ML-2: not used)
    18 LVDD2 led supply voltage +5V
    19 GND2 ground
    20 COSI crystal in | clock in (21.725 MHz)
    21 COSO crystal out
    22 VDD supply voltage +5V
    23 GND1 ground
    24 TEST1 (wired to GND)
    25 TEST2 (wired to GND)
    26 TEST3 (wired to GND)
    27 /RESET reset 
    28 AVDD analogue supply voltage +5V
    29 OUT sound out
    30 AGND analogue ground
    31 KI0 key matrix in
    32 KI1 key matrix in
    33 KI2 key matrix in
    34 KI3 key matrix in
    35 KI4 key matrix in
    36 KI5 key matrix in
    37 KI6 key matrix in
    38 KI7 key matrix in
    39 KO0 key matrix out
    40 KO1 key matrix out
    41 KO2 key matrix out
    42 KO3 key matrix out
    43 KO4 key matrix out
    44 KO5 key matrix out
    45 KO6 key matrix out
    46 KO7 key matrix out
    47 KO8 key matrix out (not used)
    48 KO9 key matrix out (not used)
    49 KO10 key matrix out (not used)
    50 KO11 key matrix out (not used)
    51 D4  rom pack bus
    52 D3  rom pack bus
    53 D2  rom pack bus
    54 D1  rom pack bus
    55 OP  rom pack /adress data
    56 ø2  rom pack clock2
    57 ø1  rom pack clock1
    58 CE  rom pack enable
    59 LGND1 led ground
    60 LY0 led matrix out

    In PT-88 the unused CPU pins 47, 49, 50 stay hi and 48 stays lo.

    Midsize key variants of this instrument (polyphony 4 notes) were released as Casio PT-380 (polyphony 6 notes, microphone), as PT-480 (different case, additional "voice changer" +/- buttons, sold in Spain and Poland?). Another rare version (voice changer, 8 additional effect pads, case and concept resembling PA-31) was Casio PA-81 (as Japan version PT-580). A Japanesse midsize variant with 3 flashing metronome LEDs and "Do Re Mi Guide" (see CT-840) was Casio PT-680. (I don't know if due to sing samples it uses a M6567 CPU like in CT-840, but the panel layout looks like a PT-88 variant.)

    A successor of this hardware class (no ROM-Pack slot) was Casio ML-1 and ML-2.
     

     removal of these screws voids warranty...    
    WarrantyVoid
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