CYBERYOGI =CO=Windler

Measuring -15V on a positive voltage sounds very malicious. My Nokia 417TV (low emission SVGA CRT monitor with high resolution PAL TV) had an atrocious design flaw the destroys irreplaceable special ICs. Namely in the power supply of the TV PCB it contains a positive and a negative voltage regulator. The positive regulator LM2940CT has an awful feature because it was designed to be also suitable for battery chargers, and so for safety (to protect against wrongways battery insertion) turns itself off if during power-on it detects any negative voltage residue on its positive voltage output. So if e.g. by moisture or leaky capacitors that line goes only slightly negative, it will selfdestruct because it output no positive voltage, and so current through the rest of the circuit pulls it even further negative, destroying the RGB amp IC and TV section microcontroller (which is impossible to find).

I guess it only would hum or increase other noises (keyboard matrix beep etc.) if 1000 instead of 2200uF was used. I can not imagine that this disables tone memory. If it was nF instead of uF it might have been possible, but the difference is not extreme enough to make it fail completely. This is not a supercap that holds enough charge to power a chip for days, any these old ones even ran warm and are nothing that runs on a few microamps.

🤔 You wonder about a CZ accordion? Then check out the Commodordion... 🙂

Desolder the transistor and test again. If any of its 3 pins have a low resistance short circuit, the thing is toast and needs to be replaced.

May be the melody envelope capacitor is bad (internal high resistance short circuit). In the almost identical PT-30 it is connected to pin 79 of the CPU D1868G (aka HD61703). Also battery leak acid spilled at its pins may have made the PCB material conductive at it and so short that pin.

If something digital plays dead, always check the reset capacitor. If it is decomposed or shorted (e.g. by battery liquid) the thing won't wake up at all or crash. Also faulty quartz or clock oscillator can make strange trouble.

What a crazy thing is this? The design looks like a bigger version of Casio DM-100, but according to the preset sound list it also seems to have a PD sound source.

Check the sustain pedal jack connections. Many early Casio keyboards play infinite sustain (until polyphony runs out) so long the sustain pedal is held. Hence a shorted contact or capacitor there would cause infinite sustain. Technically the sustain pedal is part of the keyboard matrix (simulating a non-locking button press) but likely has an additional transistor or 4066 IC etc. for decoupling it from the rest of the matrix (to make it DC controlled). If the part shorts, you get infinite sustain. In my Casiotone 401 with the "memory" switch the current chord is held after key release (with or without rhythm). The chord voice uses a different chip TMS3615, which analogue sustain length control voltage is at pin 3 (datasheet falsely claims 4). AFAIK in Casiotone 403 the main voice sound CPU is a D990G (a bugfixed D776G?, like in MT-60) that activates its "hold" (sustain) pedal through a diode from pin 17 to 25. The sustain switch is 17->26.

Nope, confusing polarity tends to destroy the CPU itself, so the thing is braindead (in Germany we call that now "vermariupolt" - as a pun of the word "verpolt" = "reversed polarity" and allusion to the name of the Ukraine city that was completely bombed away into ground). Battery leak vapour is mainly disastrous to LCD, the rest usually can be fixed.

Also Casiotone CT-7000 and RZ-1 had datasette "MT" feature. And for Casio PT-50 and PT-30 was the upgrade module TA-1 to save sequencer content on tape.

Do NOT use insulated cables - they are too thick and put even more strain on the PCB. I had badly messed up my VL-10 when I upgraded it with VL-1 functions and had to remove all that cable mess to use hair thin coil wires instead. To patch PCB traces, simply use individual thin copper wires from a wick cable. Also enamelled coil wire can be used (remove insulation by soldering iron heat before pressing into place). The graphite/carbon traces can be patched with copper wire too (resistance is not critical here). Only those directly under the black rubber contacts may suffer of oxidization or mechanical wear when soldered directly underneath (but they will function too). You may buy conductive carbon paint instead, but it is not really necessary here. Here I posted a photo of a patched PT-50 chord keypad PCB that got damaged much worse than yours. https://www.casiomusicforums.com/index.php?/topic/22041-pt-31-wont-power-on-where-to-start/#comment-84290

Perhaps midi pitchbend features may be used for this (at least if played from sequencer). But I don't know if normal keyboards support polyphonic pitch changes for individual held notes.

Did it ever suffer of battery leak? The corrosive vapours eat through the electronics (particularly in moist environment) and particularly damage LCD. But also copper traces and through-hole contacts of the PCB can go bad. Tiny black spots under the green laquer of a copper trace hint that it may have corroded through and lost conductivity.

The original CZ-101 and CZ-1 technology is fully understood and even found its way into MAME to emulate the inner working. So it would be time for Casio to build a modern remake with more features and perhaps a variant of the original engine with higher parameter resolution and perhaps control knobs and waveform display etc. I would be more interested in a classic SA-series remake with access to all internal sound parameters (important: without depending on any shortlived app crap and bluetooth radiation) and USB jack (midi and possibly USB stick support). IMO it should become a small but not excessively cheapish keyboard similar like Yamaha PSS-A50, so e.g. velocity sensitive midsize keys would be nice.

I wrote in this thread about the CPU pinout. PT-20 is a crippled PT-30 variant and barely related to PT-80. https://www.casiomusicforums.com/index.php?/topic/21503-casio-pt20/#comment-79847 The RAM is special. I wrote down the pinout eons ago. pinout HD61914 The "Hitachi HD61914 x" (44 pin SMD, pins count anticlockwise, x = a letter) is a 4 bit SRAM with built-in "self control circuit" that was used in Casio keyboards with D1868G CPU and programmable calculators (with CPU "Hitachi HD61913 xxx"). The "HD" and letter are printed above the "61914". Said letter can be absent, A, B or C; it is unknown whether it indicates the memory capacity or speed or other special functions (e.g. address decoding scheme); at least the version without letter has 1 KByte capacity (2048 words x 4 bit, seen in Radio Shack PC-4 service manual). Most important is that the first 11 pins have the same pinout like a ROM-Pack and so version B was also used in the special RAM-Pack RA-1 for Casio PT-50. In PT-30 the HD61914B apparently uses 3 additional pins 14, 17, 19 multiplexed with keyboard matrix and datasette port (may be NC to ease PCB layout). My 2nd (likely older) PT-30 contains a HD61914A (not and has an additional IC "TC40H000P" (4x NAND). In PT-50 both SRAMs are basically wired parallel. The only main difference seems pin 28 that is +Vs on the left IC but cpu pin 30 (VDD2) on the right. SRAM pins 1..12 go to the cpu, while 24..27 and 29..33 are on +Vs. Although pins 34..44 are connected with various pins from 1..11 (see here), I expect that they are NC and only used to simplify the PCB layout. But since VDD2 is only a standby signal, it may be that there is indeed a deeper meaning behind this (possibly decoded by some odd XOR tests). Pins 13..23 definitely do nothing and thus are very likely NC. Also in PT-30 3 SRAM pin traces are additionally wired to other pins (6 to 19, 7 to 17, 11 to 14), those are likely NC to ease wiring. SRAM pin 6 (clock phase?) is wired through a diode to CPU pin 28. In my 2nd PT-30 SRAM pin 6 is additionally wired through another diode to the output of a driver (2 chained NANDs) from CPU pin 30 and some RC network circuitry to to the power switch "off" contact (likely to prevent data corruption), which hints that SRAM pin 6 is always input. It is unknown what pins 24..33 exactly do; in the pocket computer Radio Shack PC-4 (HD61914 with no letter) they are all wired to pin 1 and the optional RAM-Pack (pinout like a ROM-Pack) is simply wired parallel to the internal SRAM. That RAM-Pack (only empty PCB layout shown in service manual) apparently contains a single "HD61914 x" with pin 1 wired only to pin 33, pins 2 additionally to 23, pin 3 additionally to 22, pin 4 additionally to 28, pin 27 only to 29, connector pin 1 to IC pin 24. These additional pins likely map the address range for the 2nd RAM at $800h directly above RAM 1, which in the PC-4 starts at $200h above the CPU internal RAM. Additionally the traces to pins 3..11 are wired through 21..13, and pins 34..44 are all interconnected (likely NC to ease wiring). But by their wiring at least pins 22 and 23 seem to be not NC (contrary to their naming in PC-4 schematics). Also in RA-1, PT-30 and PT-50 there are many such connections, of those many pins may be NC to simplify the PCB layout. In the PC-4 the cassette interface port (to an 28 pin DIL IC HD43110 for data compression, 300 baud "Kansas City standard", serial data on D4) is wired parallel to the RAMs and only uses a different ø2 clock line from the CPU, which shows that Casio used this 4 bit bus in many places. This pinout is based on the service manual of the BASIC programmable pocket computer Radio Shack PC-4 (rebranded Casio PB-100) and the website of Piotr Piatek (thanks to him). The PB-100 was a crippled version of Casio FX-700P, which had an additional function button and the 2nd RAM already built-in (no RAM-Pack slot), marketed in 1982 as scientific calculator. caution: The service manual indicates that this IC uses "negative logic", i.e. technically +5V is its GND while 0V is its -5V supply voltage. So the voltages are not was the pin names suggest. I use the positive voltage naming convention (from 0V to +5V, not -5V to 0V). pin name purpose 1 GND supply voltage +5.5V 2 CE chip enable 3 VDD1 ground 0V 4 VDD2 auto-power-off voltage (hi when off) 5 ø1 clock1 6 ø2 clock2 (phase shifted against ø1) 7 OP data /address select 8 D1 address/data bus 9 D2 address/data bus 10 D3 address/data bus 11 D4 address/data bus 12 INT (interrupt?) 13 NC 14 NC 15 NC 16 NC 17 NC 18 NC 19 NC 20 NC 21 NC 22 NC (device address select?) 23 NC (device address select?) 24 DC (alternative backup battery supply voltage?) 25 V4 device address select 26 V3 device address select 27 V2 device address select 28 V1 device address select A11 29 R/W (device address select?) 30 BL4 (device address select?) 31 BL3 (device address select?) 32 BL2 (device address select?) 33 BL1 (device address select?) 34 NC 35 NC 36 NC 37 NC 38 NC 39 NC 40 NC 41 NC 42 NC 43 NC 44 NC According to Piotr's website the write command is $4 (OP=0), followed by a 4 bit device address, followed by the 11 bit address within the device (MSB is ignored). After this any amount of data can be written (in an OP=1 cycle), which makes the address counter advance after every 4 bit word. The read command is $0 and works similar. A single $0 word regularly appears on the bus when the calculator is idle, which may be a kind of soft reset.

Perhaps there is a hairline crack in a PCB trace that only reconnects so long the case was open. Otherwise I would rather expect cats to pee inside (which is nearly as corrosive as drain pipe cleaner and needs to be washed off the PCB immediately) =>use your nose.

I got a poor photocopy of the Casiotone 403 service manual but have no intact scanner. I wrote about the hardware here. If functions have failed after opening it, check for panel PCB trace damage. The metal case tabs in my 401 are sharp like razor blades and easily damage PCBs by accidentally scratching its surface.

I have no Discord access. (I am not part of any antisocial media except Youtube.)

I got a poor photocopy of the Casiotone 403 service manual but have no intact scanner.

They really own Moog? Their Alesis budget keyboards seem to be near-toy-grade trash like nowadays Bontempi.

The black blob won't contain any complete hidden chip (this is no pay-TV decoder) but a bare piece of silicon. This is not a camouflage measure against hackers uploading unwanted data but simply cheapened hardware design because this is pointless. (Pirating the keyboard by a small company would be more expensive than buying the real thing.) The flash IC for sure can be desoldered, but nothing can be done if the COB chip or its firmware went bad. I read on MAME forum that some Casio stuff used custom variants of a standard microcontroller that has changed opcodes to prevent commercial hardware pirates to run the Casio rom content on an off-the-shelf version of that MCU. Casio has no reason to prevent reinstalling of the original firmware, and unlikely worry that any hobbyist loads custom sound sets on it or such things. A few mad scientist nerds messing with their hardware won't make anybody bankrupt nor prevent them from buying the next model. E.g. some hobby hackers managed to decode the firmware of the food processor Thermomix, which indeed was surprisingly well protected and encrypted. But the reason for those complex measure was that the manufacturer obviously already had planned to permanently connect it to the internet through wifi (which was done in the successor), which required this to prevent dangerous harm by malware (that else might have been capable to set a kitchen on fire or scald the user). A music keyboard is less dangerous than a device that can cook and grind food (or the users hand), so it needs no extreme protections. It would not surprise me if there is even a hidden debug/service mode in the XW keyboard to reinstall firmware without desoldering. But this is likely something cryptic like hooking up a serial port to some test pins and bridging some others and sending special binary code to that port, that is almost impossible to find out by trial and error (bearing the risk of frying the rest).

I guess of Alesis is only the brand name left, bought for cheap by a random Chinese company. My only Alesis product (beside the reverb chip in some early 1990th Farfisa and Orla stuff) is the toy-like "Alesis Melody 32" (aka "Harmony 32"), which looks like made by Medeli (may be even Yongmei) and contains a sample based Holtek chip with 300 grainy 8-bit(?) preset sounds and USB midi. Although playable, it is a really faithless products that feels like quickly botched together to make some bucks. E.g. the tiny drumpad buttons have latency and make glitches when held down during play (by lack of matrix diodes), the demo songs suck and rhythms are boring. They did not put much effort into its software to make it a pleasant experience. Unlike modern Yamaha PortaSound or a Casio VL-1 it not even has an octave switch for its 32 midsize keys. So I would not expect anything great of nowadays Alesis, not to say to keep the experts to service their old stuff.

If there gets salt water (or any acidic stuff like cola or lemonade) inside, immediately remove batteries, because electricity rapidly worsens corrosion. If you clean anything with vinegar (makes only sense with alkaline battery spill), be sure to rinse off the vinegar too, which is almost as corrosive as the salt itself!

Also the rom differs between SK-8 and SK-5, hence it has a different set of sounds and rhythms. Casio SK-8: 8 OBS preset sounds {piano, vibraphone, guitar, pipe organ, trumpet, violin, flute, clarinet} 10 OBS rhythms {rock, disco, swing 2beat, swing 4beat, samba, bossa nova, beguine, march, slow rock, waltz} Casio SK-5: different main features: neither ROM-Pack slot nor key lighting different preset sounds {piano, vibraphone, dog, surf, trumpet, pipe organ, chorus, flute} different preset rhythms {rock 1..2, disco 1..2, 16 beat, march, bossa nova, samba, slow rock, waltz} 4 additional drum/ effect pads {lion, laser gun, hi bongo, low bongo} 7 demos (complex polyphonic arrangements)

You may temporary jam the select button by sticking a thin piece of sheet plastic (e.g. blister packaging) in the gap at the side of it. That's no proper solution but helps to hold it down.