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 Forum index » How-tos » Manuals, Instructions, and Documents
Symphonytron 8000: service manual wanted (dead MB-1)
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CYBERYOGI =CO=Windler



Joined: Aug 05, 2012
Posts: 9
Location: Germany

PostPosted: Sun Aug 05, 2012 8:29 pm    Post subject:  Symphonytron 8000: service manual wanted (dead MB-1) Reply with quote  Mark this post and the followings unread

On eBay I bought parts of a Casio Symphonytron system. I don't own the entire stage organ system but only 1 CT-8000 keyboard, the MB-1 sequencer (dead) and the RC-1 drum machine, but no pedal board. It came without the CIDI (Casio's Infernal/Inferior/Internal/Instrument Digital Interface) cables, so I ordered 3 DIN14 cables for Atari ST floppy, those work well. At least the RC-1 plays accompaniment key split mode with arpeggio through the keyboard, which proves correct digital communication.

Unfortunately my Symphonytron sequencer unit MB-1 is dead (does nothing, but plays note mess when touching the crystal etc.), so I am not sure if its eprom may have failed (dump does not change by reducing Vcc) or it might be still a bug by the lack of original CIDI port cables.

- need service manual

Long ago I already downloaded the complete Symphonytron user manual from an eBay link. It is huge, thus I can not upload it here because internet is expensive at the moment. (Internet-by-Call on analogue modem costs currently 0.40ct/min on the only provider that yet hasn't frauded me.) I have photographed all the PCBs from both sides, but I have no schematics. Has anybody a service manual?

WARNING: Do NOT send it by e-mail without prior notice. (Better upload it elsewhere.) I have only an analogue modem (4.4kbps) and so I can not easily receive e-mails larger than some 100KB.

- hardware details

Did you know that early Casio keyboards had a CPU compatible with Intel 8049?

Unfortunately the "Willem Pro4 isp" eprommer had a way too weak power supply with tiny SMD transistors switching the voltages. One was burnt anyway, so I had to install bigger non-SMD ones to get the MCS-48 adapter to work. Casio "D8049C xxx" ICs need Vcc of at least 4.5V to read properly, which was impossible with the original transistors ans PSU (it gave only 4V even in 5.6V mode). I installed a 10kOhm resistor into the EA line to avoid damage by the +12V if the IC would not have supported it properly, and connected it to a 5kOhm potentiometer to vary the voltage, which I didn't need. (Too high EA voltage (15V) outputs only "00" while too low voltage (9V?) makes the CPU run its program and output garbage. At too low Vcc it repeats the first part of the rom again and again.) So I e.g. could read the firmware of the Symphonytron Casio CT-8000 cpu and Casio HT-6000 synth (its D80C48 seems to be a real CMOS IC that draws less current). Also MT-36,MT-40,MT-90/MT-200 and Casiotone 401 have such a CPU.

- Does anybody know more about Casio D930/D931 ICs?

The only texts I found about them is on the website firstpr.com.au by Robin Whittle.

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