Circuit Overview:
DCO machine with analog filter. The HZ-600 came first apparently to be followed by the versions with speakers included and auto-accompaniment feature. The SD (Spectrum Dynamic) synthesis is some kind of pulse additive scheme it appears offering dynamic interaction in the process. HT-700 has 4 octaves of smaller keys, HT-3000 full sized keys, and HT-6000 (released in'88) is 4 dco/voice 8 voice to take the most dco's record. However I would like more information. I read that MIDI implementation is pathetic (no sysex?). Somehow it's hard for me to imagine that the machine contained 8 vcf's but author of link above claims it's polyphonic filtering. Maybe he means it has retrigger option of the shared filter :-). It just seems..so...so...uncasio to include one actual piece of analog hardware..not to mention 8 of them! ;-) But for sure there is one I've read in the HT-700 and probably the 3000 as well. My little HT700 is charming! 8 voice poly and there appear to be two filters. One for chord and one for melody voicing. Haven't figured it all out yet but have messed with paramters and you can ..make some great sounds! 1st class machine! I fell into some compelling grooves using some of the patterns that really are good backbone tracks immediately. You'll be hearing from this bad toy :-).
Service Tips:
I got one with a power supply that didn't fit the jack right. Those casio's use..what is it 1.7mm or something instead of 2.1mm. It'll act like the solder's broken but it's isn't :-). Those JRC2090's I can't find much info on. Imgine if they break it's a pain to find a new vcf possibly. Could be they're similar enough to 13700's or 13600's. But Casio likes to use their own parts it seems and when they break that's it. So I wouldn't count on it being economically feasable to repair these if anything bad happens. Some of their stuff will even blow a cpu if power gets inverted I found recently with a 1990 ish portable piano unit.
Parts:
Let me know if there are common failing parts in these.
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