Yamaha PSS-16 (beginners FM keyboard with accompaniment & demos)

This FM keyboard from 1997 is nothing really great and behaves unpleasantly stubborn and unflexible, but it has many demo musics. Its special features are the "ad-lib" (simply a pre- programmed monophonic melody fill-in track) and "harmony" (trio) function, those Yamaha gladly named "computer aided music".

Although it has in total 100 preset sounds, many of these are simply variations of other with additional chorus, layer ("dual voice") or key split sound combinations. All preset sounds are simple 2 operator FM imitations of natural instruments those sound a little harsh and contain nothing avantgardistic or tekkno-like. The 22 preset rhythms have an optional single finger accompaniment (only a few standard chords) and consist of only 4 thin sounding low- res percussion samples. There are also 4 rubber drumpads for them. This instrument was previously released in 1990 as Yamaha PSS-190 (with blue drumpads and boring black control panel).

main features:

eastereggs:

notes:

The user interface of this instrument has various similarities with the Yamaha PSS-31. Very annoying is that Yamaha divided the preset sounds into groups with or without chorus, layer ("dual voice"), key split etc. with only quite few sounds per group. Why didn't they instead add separate OBS effect buttons (or at least effect function numbers or similar) to let the user decide to add such effects to any preset you want?! (The great Yamaha PSS-390 had a separate "dual voice" and "sustain" button like it should be.) The cipher buttons and "enter" play a hihat noise, which disturbs live play. The "enter" button is basically useless because all preset sound numbers consist of exactly 2 digits; by my knowledge no other Yamaha beginners keyboard has this stupid button.

The main voice sounds of this instrument are plain ordinary 2-operator FM. Unfortunately the sound set is strictly focussed on natural instruments (fairly realistic imitated) and include no typical synth or tekkno sounds. No even the "mandolin" rings. The "ensemble" and "dual voice" sounds layer 2 subvoices to create more complex timbres. The "harmony" button turns the main voice into a monophonic trio. During accompaniment it plays in the corresponding key.

(The full sound list can be found in the manual of this instrument, downloadable on the Yamaha Manual Library site.)

The "ad-lib" button plays for the duration of a bar (or so long the button is held) a monophonic jazzy improvisation part in the style of the selected rhythm. It can be played to it, and with accompaniment it plays in the same key. This concept exists in a more versatile and sophisticated form also in Kawai keyboards like the Kawai MS20 or MS720.

The rhythms consist of only 4 thin sounding low- res samples, and selecting a new rhythm (white keys + select button) waits until pattern end before the change takes effect. The single finger accompaniments sound good and employ many different sounds, but they behave static and unlike e.g. the great Yamaha PSS-390 there are neither fill- ins nor intro/ ending features. The disco patterns are nice, and their rough and slightly harsh sound style has some similarities with Casio MA-130, despite the PSS-16 has FM timbres while MA-130 is completely sample- based. Unfortunately there are no separate rhythm or accompaniment volume controls, and there is no manual chord mode without rhythm, which is particularly annoying because only during accompaniment the key of the "ad-lib" and trio sounds can be changed.
 

circuit bending details

The Yamaha PSS-16 is based on the single-chip CPU "Yamaha YM7137 3D" (crystal clocked @ 3.58 MHz) with amp IC AN7148 (12 pin SIL). The hardware of PSS-9/PSS-50 and the fullsize PSR-2/PSR-3 are more or less castrated versions of these.

Also PSR 18/19 are similar, but have apparently small rom changes (CPU "YM71374E") to control an additional digital reverb chip YM7133A (LRV, with external DRAM).
I haven't analyzed this hardware by myself, but Traktor told me about it and I examined schematics.

keyboard matrix

This keyboard matrix is based on partial schematics photos of Yamaha PSS-190 and PSS-50, and the service manual of Yamaha PSR-3. The keys are grouped by 6. The lower octave is only available with installed diode 'model select 3'.
 
27 N0
28 N1
29 N2
30 N3
31 N4
32 N5
 
CPU pin
in 1
in 2
in 3
in 4
in 5
in 6
in / out
 
o
C1
model select 1
[diode]
model select 2
[diode] 
model select 3
[diode]
 
 
out 1
35 B0
o
F#1
o
F1
o
E1
o
D#1
o
D1
o
C#1
out 2
36 B1
o
C2
o
B1
o
A#1
o
A1
o
G#1
o
G1
out 3
37 B2
o
F#2
o
F2
o
E2
o
D#2
o
D2
o
C#2
out 4
38 B3
o
C3
o
B2
o
A#2
o
A2
o
G#2
o
G2
out 5
39 B4
o
F#3
o
F3
o
E3
o
D#3
o
D3
o
C#3
out 6
40 B5
o
C4
o
B3
o
A#3
o
A3
o
G#3
o
G3
out 7
1 B6
o
F#4
o
F4
o
E4
o
D#4
o
D4
o
C#4
out 8
2 B7
o
C5
o
B4
o
A#4
o
A4
o
G#4
o
G4
out 9
10 B8
volume
-
volume
+
tempo
-
tempo
+
select
stop
out 10
11 B9
P.
base
P.
snare
P.
hihat
P.
cymbal
ad-lib
harmony
out 11
12 B10
demo
'1'
'2'
'3'
'4'
'5'
out 12
13 B11
enter
'0'
'9'
'8'
'7'
'6'
out 13
14 B12

The input lines are active-low, i.e. react on GND. Any functions can be triggered by a non- locking switch in series to a diode from one "in" to one "out" pin.
 

legend:
"o"
 = keyboard key
P.
 = drumpad
orange
background 		 = easteregg (unconnected feature)

I haven't tested anything of these by myself, but Traktor told me by e-mail about this. The Yamaha PSR-18 has 'echo' and 'reverb' instead of  'volume -' and 'volume +' and supports 61 keys by additional matrix output pins 15..17.

fingered accompaniment

In Yamaha PSR-3 the power/mode slide switch {off, normal, single finger, fingered} can also select fingered accompaniment. This locking 4 position switch pulls in 'single finger' mode cpu pin 33 (N6), and in 'fingered chord' mode cpu pin 34 (N7) through each a 2.2k resistor to GND. In 'normal' mode it is open, and in 'off' mode it disconnects power by pulling the base of a transistor to GND. Thus install a locking switch with 2.2k resistor from pin 34 to GND to enable it. It may be a good idea to wire here a 2 position switch in series to the single finger chord contact to make it select between pin 33 and 34.

keyboard length, octave switch, key split position

Traktor identified in schematics a model select feature of the "YM-7137 3D" CPU to change the octave setting and keyboard length by a fixed diode from pins 28..30 to 35. You may install a switch in series to a diode here, but regard that will be only recognized during reset.

model select 1 = PSS-190/PSS-16
model select 2 = PSS-50/PSS-9
model select 3 = PSR-2/PSS-3
 
model select 1 model select 2 model select 3 chord spit point octave keyboard length
X
 
 
 C#1 hi 37
 
X
 
 F#1 hi 37?
 
 
X
 C#1 lo 49

It is unknown whether the 'model select 1' diode is necessary at all or anyway the default mode of the CPU.

In PSR-18 schematics I see no such diode, but its CPU "YM71374E" has a changed rom to control a reverb IC and 61 keys. According to d-tech, Yamaha PSR-100 has the software number "5F".

According to schematics photos, the original PSS-190 and PSS-50 CPU is "YM7137" (part no. XH242A00) and so may slightly differ from the "YM-7137 3D" (X1257A00) of the others. Traktor told me that in his PSS-190 only in "model select 1" mode the output of dual voice sounds is stereo (else both pins output the same). Its fingered chord split point in all 3 modes is F#1.

More advanced fullsize variants (61 keys, CPU "YM7137 4E", reverb & echo by additional IC) were Yamaha PSR-18/ PSR-19 (mentioned by d-tech, who analyzed this CPU). D-tech mentioned that Yamaha PSR-100 has software number "5F".

pinout YM7137 (OPJ)

The FM Tone Generator "Yamaha YM7137 xx" (40 pin DIL, xx = software number of internal rom?) is the CPU of various 1990th beginners keyboards with "Ad-lib" button. It contains 8 note polyphonic 2 operator FM sound hardware with lo-fi sample percussion. Beside its single chip mode, it can be also used as a sound IC controlled by an external CPU (set by 2 mode select pins). According to d-tech, the OPJ sound engine is similar like OPK, but lacks firmware features for realtime envelope control. Hence the only 4 PCM percussion samples likely use heavy dynamic compression with volume envelope. The keyboard matrix supports up to 16 outputs and 6 inputs.
 
software number hardware class notes & features
(none) (PSS-190) part no. XH242A00
3D PSS-16 same like PSS-190?
4E PSR-2 61 keys, reverb ic LRV support
5F PSR-100 49 keys

This pinout is based on partial schematics photos of Yamaha PSS-190 and  PSS-50, and the service manual of Yamaha PSR-3.
 
pin name line purpose
1 PB6 B6 key matrix out
2 PB7 B7 key matrix out
3 VSS   ground 0V
4 PD0   PSR-18: SEL0 (to reverb ic)
5 PD1   PSR-18: SEL1 (to reverb ic)
6 PD3    
7 PD4    
8 PD2   PSR-18: /IC
9 PD5    
10 PC0 B8 key matrix out
11 PC1 B9 key matrix out
12 PC2 B10 key matrix out
13 PC3 B11 key matrix out
14 PC4 B12 key matrix out
15 PC5 B13 PSR-18: key matrix out
16 PC6 B14 PSR-18: key matrix out
17 PC7 B15 PSR-18: key matrix out 
18 /OSC   crystal in (3.58MHz)
19 XOUT   crystal out
20 /RES   reset
pin name line purpose
21 M0   mode select in
22 M1   mode select in
23 AGND   analogue ground 0V
24 OUT2   analogue sound out
25 OUT1   analogue sound out
26 VDD   supply voltage +5V
27 PA0 N0 key matrix in
28 PA1 N1 key matrix in
29 PA2 N2 key matrix in
30 PA3 N3 key matrix in
31 PA4 N4 key matrix in
32 PA5 N5 key matrix in
33 PA6 N6 single finger chord switch in
34 PA7 N7 fingered chord switch in
35 PB0 B0 key matrix out
36 PB1 B1 key matrix out
37 PB2 B2 key matrix out
38 PB3 B3 key matrix out
39 PB4 B4 key matrix out
40 PB5 B5 key matrix out

The operation mode of this IC is controlled by 2 mode select pins (seen in PSR-3 service manual), which is recognized only during reset. I don't know details, but d-tech has analyzed the data protocol how to control the YM7137 by an external CPU. All released keyboards seem to use only the "single chip mode", so the rest may have been intended for prototypes or testing.
 
M0 M1 mode
0 0 expansion mode 1
0 1 expansion mode 2
1 0 single chip mode
1 1 external CPU mode

In mono keyboards like PSR-3 and PSS-50 the audio out pin 25 (OUT1) is unused.

The key matrix input pins 27..33 and also 11..14 (because they use an I/O port of the microcontroller) have each a 47k pullup resistor.

Interesting is that the clock frequency 3.58MHz matches Holtek - Ad-lib Micro®, a single chip sound microcontroller series which was the heart of My Music Center and similar 1990th toy grade tablehooters. Despite these don't support FM and sound more primitive, they combine synthesized electronic main voice tones with lo-fi sample percussion and thus may have technical similarities. E.g. in Holtek HT3670 even pin names of matrix ports {PA#, PB#, PC#, PD#} match, and port PA is used for key matrix in.

The PSS-16 has a song bank of 15 polyphonic demo melodies. They are not bad, although these ones are way simpler orchestrated than on Yamaha PSS-6 or PSS-31 and sound rather establishment.

  1. Joy to the World
  2. Brother John
  3. The Old Folks at Home
  4. House of Rising Sun
  5. A Little Brown Jug
  6. Silent Night
  7. Jingle Bells
  8. Ave Maria
  9. Die Lorelei
  10. Camptown Races
  11. When the Saints Go Marching In
  12. Brahms' Lullaby
  13. Yesterday (Beatles song)
  14. Hey Jude (Beatles song)
  15. Venus
The demo button only starts "Venus". Other songs are selected through cipher buttons; when selected this way and the demo button is pressed while the demo is playing, the main voice is muted and thus the player can improvise to the demos. Every song repeats in a loop when not stopped. Interesting is that many of these songs were previously also released on Casio ROM- Pack cartridges, thus Yamaha apparently copied the selection from them, although the Casio arrangements sound nicer and more complex.

A shorter mono variant of the PSS-190/ PSS-16 was released as Yamaha PSS-50 and PSS-9. These have only 32 keys and thus lack the first 3 rhythms and 2 demos (since they are selected by the missing 5 leftmost keys) and also lack drumpads. Unlike the light blue control panel of the PSS-16, the PSS-9 panel is brown. A fullsize version with one speaker was released as Yamaha PSR-2/ PSR-3 (49 keys, fingered chord, no drumpads, no 2nd functions on additional keys) and with 2 speakers as PSR-100 (all seen on eBay).
 

 removal of these screws voids warranty...    
WarrantyVoid
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