squarewave tablehooter with unique percussion

This extremely rare squarewave tablehooter is based on an odd monophonic variant of Hing Hon EK-001 sound generator. Interesting is that the preset sounds and the great impulsive POKEY percussion timbres are different. Unfortunately the instrument is detuned by 5 full notes(!) and the plastic is terribly fragile. Also the leftmost 2 keys and the 5th drumpad are fake.

warning: Never send a keyboard with this case through mail without multiple centimeters(!) of padding (styrofoam, firmly crushed paper, fanfolded cardboard or similar), because the plastic is brittle like glass and will unavoidably shatter into a zillion of pieces as soon they toss it around in the mail. (Older Yongmei keyboards original packaging contains no end padding at all and thus is absolutely unsuited(!) for mail shipping.)
 

My Yongmei MS-210B arrived with its right end smashed to about 30 small debris because the vendor didn't pad the case end properly but despite warning only wrapped the original box in a thin layer of bubble wrap, which is in no way sufficient. A year before that I had ordered a MS-110A with identical case, that was shattered similarly, but when I reported that damage in a Deutsche Post post office, the spirt- nosed post office clerk smeared a few words across the damage report form (instead of filling out the entries), intentionally smashed the remains of the wrapped keyboard with a huge 20kg parcel on a trolley and sent it back to the sender despite I explicitly requested to sent it back to me after damage analysis. I never saw that keyboard again nor I got any money back. Thus I did not report the incident with the shattered MS-210B to a post office again, but puzzled it together with a lot of superglue, which took a full day.

The case style of the MS-210B still looks very much like a Yongmei transistor tooter (see Golden Camel-7A) despite it already contains digital hardware. Interesting is that the letters "MS-" on the control panel here suggests the abbreviation "Musical Source", while they normally are associated with Miles, MeiKe, Meiker or the genuine name of the manufactures Meisheng. Like with other Yongmeis, also here the manual contains a lot of false claims, and this one is especially ridiculous, thus I quote it here since the text proudly advertises this tablehooter in the style of earliest 1980th ads for a Roland TB-303 ("computer controlled"...) or similar:
 

*) In fact it is completely monophonic. **) It is genuinely detuned by 5 full notes (i.e. 500 cent; 'C' is on 'G') instead of having "Tone Quality < 3CENTS" like claimed in its feature list. ***) In reality the amplifier is completely mono.
 

There is a big button with the fancy name "computer start" and 12 white keys are marked with cryptic looking green letters (which awakes memories to the great age of of Casio's early 1980th keyboards). Unfortunately this mysterious button turns out to be only the standby on/off switch, which needs to be pressed additionally to the normal power switch to turn the instrument on, and the standby not even turns off the internal amplifier, which voids the wannabe auto-power-off feature of the "computer" to save batteries. The manual also mentions a mysterious "Encircled Sound" button, which in fact seems to be the 3rd slide switch which simply makes the main voice duller by a capacitor. (I could imagine that the name "Encircled Sound"  was genuinely the Chinese to Engrish translation for stereo chorus - a feature that would make no sense in a mono keyboard anyway.)

main features:

• 42 midsize keys + 2 fake keys for one key play
• 2 built-in speakers (mono)
• monophonic main voice
• 8 OBS preset sounds {trumpet, ukulele, piano, saxophone, music box, flute, oboe, church bell}
• 8 OBS preset rhythms {ballad, 8 beat, rock, chacha, waltz, beguine, swing, march} with unique percussion
• master volume slide switch (3 steps)
• tempo +/- buttons (16 steps)
• muffle slide switch (mislabelled "sustain")
• vibrato & sustain button (vibrato modulates CPU clock)
• 4 drumpad buttons {bell, base, snare, hihat} (wrong icons show {bell, snare, open hihat, close hihat}, fake 5th button starts demos)
• sound generator like Hing Hon EK-001, but with only monophonic main voice and different percussion. The piano sound ignores key press duration.
• percussion {bell, base, snare, hihat} resembling Hing Hon EK-001 (great impulsive POKEY blip sounds).
• CPU= "210" (named "FE-2" in schematics, 32 pin COB)
• simple sequencer (monophonic record/ playback of 62 notes, no edit, with one key play)
• 12 demo melodies (monophonic with standard rhythms)
• partial auto- power off (doesn't turn off the amplifier)
• jacks for microphone, headphone & AC- adapter

eastereggs:

• Like in Hing Hon EK-001, when multiple sound buttons are held down simultaneously, the CPU switches quickly between the selected sounds, resulting in a rough and buzzy kind of fast arpeggiator effect (like known from C64 SID musics). Most of the resulting sounds are relatively disharmonious, but they are unique and sound quite massive. (In unmodified state some of these button combinations mess up the keyboard matrix and though cause undesired side effects like disturbing drum pads etc.)
• Holding 'waltz' together with any other preset rhythm button produces rhythm variations.
• The standby button ("computer start") can be used to chop the main voice, because decaying notes continue to decay after powering on again (the envelope capacitor keeps its charge).
• Switching power off makes held notes howl down.

notes:

The preset sounds employ the same multipulse squarewave sound generator with capacitor envelope like Hing Hon EK-001, but the timbres are programmed differently. The continuous tones (like flute) have all a slow attack phase and contain all at least 1 second of sustain (like a pipe organ). The sustain button adds a long 3 seconds sustain (or disables it where enabled) and the vibrato button adds a 6Hz vibrato. The 'trumpet' has enabled sustain (3 seconds) and sounds rather like a bright metal pipe organ rank. The 'ukulele' has a buzzy harsh timbre with 8Hz mandolin ring. The 'piano' has enabled sustain and ignores key press duration. The 'saxophone' resembles 'organ' on EK-001 (the classic sonorous multipulse squarewave pipe organ timbre with enabled sustain) but drones less impressive. 'music box' and 'flute' sounds like intended. 'oboe' resembles 'violin' on EK-001 (another sonorous multipulse timbre). 'church bell' is a metallic multipulse timbre with sustain.

The percussion has the same wonderful impulsive POKEY style like in EK-001, but the sounds are slightly different. The 'bell' is a little lower, the 'base' is a little lower and decays faster, the 'snare' is more impulsive and decays much faster (i.e. more realistic). The closed hihat is the same and also most rhythms of the MS-210B are the same; many are simply renamed. The 'rock' corresponds to 'pop' on EK-001, '8 beat' to 'disco', 'beguine' to 'rhumba'. Only 'chacha' replaces here 'tango'.

The primitive sequencer is always in record mode and records all notes until it runs out of memory. The recording can be played back with "playback" button or note by note with the leftmost 2 fake piano keys (labelled "RECORD TEST"). To enable these keys, the 2nd slide switch must be in the "on" position. Although the sequencer is fairly useless since played notes always append to its contents, it is impressive that it does not interfere at all with rhythms, thus you can start, stop and change rhythm or tempo without any effect on the playing sequence. The tempo setting has no effect on the playback speed.
 

The demo musics of this instrument are monophonic with standard rhythm. The demos are started by pressing the rightmost fake drumpad button (which turns off the green power LED). Other demos can be selected through 12 of the white keyboard keys those are marked with green letters. A little funny is that written over 2 adjacent of these keys stands here "DEMONSTR  |  ATE SONGS". When I read it first, I though: "Huh, what demon monster ate songs?!". ;-)

 

hardware details The Yongmei MS-210B is based on the CPU "210" (32 pin COB version of Holtek HT3421A). Like with the old Yongmei transistor tooters (see Golden Camel-7A), the botched hardware contains horrible cable mess; the switch contacts are of sheet metal scratching on bare copper PCB traces, and also the key contacts employ such leaf switches. At least there are polarity protection diodes to prevent battery explosion during mains operation. The mono amplifier PCB looks like in MeiKe MK-320B. Apparently the batteries were early planned to the right, a lot of cable mess inside,... and what the fuck - an iron weight! Most bizarre is that the lightweight plastic case of this Ming vase is weighted by 2 thick iron bar weights, those serve no other purpose than making it even more fragile during shipping, and if roughly handled with 6 heavy D cells inside, for sure will turn into ball breakers those shatter everything to shards. The CPU "210" (32 pin COB) is a software variant of the PHW635 found in PlaySkool PS-635. Only preset sounds, preset rhythms and demo songs were changed, but behaviour stays the same. multipulse squarewave tone generator The main voice sound generator is the same like in PlaySkool PS-635 but the preset sounds differ. Technically this is a monophonic variant of the Hing Hon EK-001 sound engine. Some multipulses have a strange dot (short dropout to lo) in their hi section. I expect this artifact to be caused by restarting the address counter at the begin of the loop point. Thus I have visually rotated these patterns to shift the dot (marked ".") to their end. (Other multipulses likely have it at a lo section, where it stays invisible.) Internally all multipulses are 16 step long; for readability I have omitted repeating parts. The 'ukulele' contains mandolin ring, but unlike the PS-635 and EK-001 'mandolin' it is not made from plain squarewave. The 'music box' is here even 2 instead of 1 octave higher (i.e. the likely highest pitch this sound engine can produce if step rate is fixed). The metallic 'church bell' timbre strongly differs from other variants with this sound engine. The multipulse bit loops look like this:   preset sound multipulse pattern comment piano 1111111100001011. (same like 'guitar' in PS-635)  oboe 1010101000110011.   ukulele 1001010001110001.   flute 11110000 plain squarewave trumpet 11100100   saxophone 1000110110010101.   music box 10 plain squarewave (2 octaves higher) church bell 1011001001001101.   keyboard matrix The keyboard matrix corresponds to PlaySkool PS-635, but sound and rhythm names differ. This matrix is based on the MS-210B schematics any my own examination. Beside separate rhythm start & -stop buttons I found no eastereggs, but here is it for comparison.   17 C1 16 C2 15 C3 14 C4 13 C5 12 C6 11 C7   CPU pin out 1 out 2 out 3 out 4 out 5 out 6 out 7 in / out   o C#5 o C#4 o C#3 P. base tempo + O. piano R. chacha in 1 18 R1 o D5 o D4 o D3  P. cowbell tempo - O. oboe  R. march in 2 19 R2 o D#5 o D#4 o D#3 P. snare R. start O. ukulele R. rock in 3 20 R3 o E5 o E4 o E3 P. hihat R. start/stop O. flute R. swing in 4 21 R4 o F5 o F4 o F3 - R. stop O. trumpet R. 8 beat in 5 22 R5 o F#5 o F#4 o F#3 - demo O. saxophone  R. beguine in 6 23 R6 o G5 o G4 o G3 (1) o G2 vibrato O. musicbox  R. ballad in 7 24 R7 o G#5 o G#4 o G#3  o G#2 sustain O. church bell R. waltz in 8 25 R8 o A5 o A4 o A3  o A2 S. clear O. piano R. chacha in 9 26 R9 o A#5 o A#4 o A#3  o A#2 S. play O. oboe R. march in 10 27 R10 o B5 o B4 o B3 o B2 S. one key 1 O. ukulele R. rock in 11 28 R11 o C6 o C5 o C4 o C3 S. one key 2 O. flute R. swing in 12 29 R12 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 R. = preset rhythm O. = preset sound ('orchestra') P. = drumpad S. = sequencer orange background  = easteregg (unconnected feature) grey background = unconnected doublet important: Because pinouts differ among CPU variants, in the following I refer the keyboard matrix pins by their "C" ("columns" = out pins) and "R" ("rows" = in pins) numbers found in MS-210B schematics. These are CPU pin names, not capacitors and resistors! waveform arpeggiator synth If you want to enable the waveform arpeggiator synth (recommended, see EK-001) wire 8 locking switches or a DIP switch block in series with each a diode to the preset sound buttons. Due to different matrix timing, it may even be that the doublets at pins R9..R12 produce additional sound variations, so 12 switches may be better.  rhythm combinations   To enable 7 additional rhythms, install locking switches or an additional DIP switch block in series with each a diode to the preset rhythm buttons. To use these, close the 'waltz' switch together with any of the other rhythm switches. (Closing more switches or other combinations does not produce additional rhythms.) Likely these rhythms were not programmed into the CPU, but are produced because 'waltz' mode changes the reading order of rhythm patterns and the additional switch selects a different rhythm pattern (rom address?) to be played. schematics Fortunately there are schematics on the back of the manual; unfortunately the CPU pin numbers are missing and also the amplifier IC seems to be different, which limits its usability. The missing preset sound and rhythm names suggest that the rom version was not specified or unfinished when the schematics was made. overview keyboard matrix & pinout wiring In the schematics the CPU is named "FE-2" and the depicted circle (between B/C and VIB pin) on it stands for the empty hole in the COB PCB that is closest to the blob. It may be that this was originally meant to mark pin 1, but I consider counting anticlockwise from the corner after the biggest gap (with the screw between trace bundles) more logical as pin 1, thus the pin labelled "210" is pin 32. The VSS pin 30 (ground 0V) is placed here differently (skipping 2 pins, but pin order matches HT3421A pad layout). The schematics shows a 2nd pin in its real place (where in HT3421A MEMO would be), leading to the middle of the IC (labelled "DEMO", which is likely misspelled "MEMO"; HT3421A datasheet claims that chip bottom is VDD, i.e. positive supply voltage, so it can't be connected there). I.e. in this COB module unfortunately the MEMO pin was omitted and internally wired to VSS, so its sequencer is always recording. Also the auto-power-off timer is still doing its job, despite by the missing BUSY pin (how stupid is that?!) it can not turn off the amplifier. So there still is a slide switch and you additionally always have to press 'computer start' (aka 'on/off' button) to make the thing work. Possibly this chip was a pirated version of "Holtek HT3421A", but the manufacturer did not know how to handle APO properly and so removed all pins he did not understand.

The 12 demos of this instrument are:

1. American Patrol
2. It Is A Small World
3. Old Macdonald Had A Farm
4. Yankee Doodle
5. This Old Man
6. Wooden Heart
7. Happy Birthday To You
8. Silent Night
9. Home Sweet Home
10. Symphony No. 9
11. Mary Had A Little Lamb
12. Twinkle Twinkle Little Star

removal of these screws voids warranty...
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