Sequential Circuits Split-8/Pro-8 -1885    Weight = 19.2 Lbs. Number mfg.= 3,000? MRP=$1195

User Manual: Manual Manor
Reset Proceedures: N/A
Operating System code:
MIDI or other control protocol: Wiki midi modes
Software related Links:
Patches: Factory .syx or SD tweaked factory (Factory w/improved volumes/minor tweaks) or Sound Doctorin' .wav Bank
Circuit Overview: below or Synthmuseum
Scematics/Service Manual: Notelt's old scan in .pdf
Common Service Issues/Tips: below
Parts Sources: Keys knobs semiconductors misc
Uncommon chips/modules used: CEM3394 'synth on a chip', AD7541 DAC, Z80cpu
General Info Links: Vintage Synth Explorer or Wiki or Synthmuseum for more detailed feature description.

Circuit Overview:
     Another 'synth on a chip' based synth but with 8 voices that can be allocated or stacked to 2 or 4/voice. No velocity however. The CEM3394 allows the S+H caps to be placed directly on the inputs so there are a lot fewer chips. 4051's just directly interface the common analog lines to the various parameters. The tune and value knobs and the mod wheel and pitch wheel are read through another 4051 to be interfaced to the common dac/ comparator adc circuitry used in most analog synths with storage. These were built in Japan for Sequential I'm told.

Service Tips:
      Many similarities in construction to Six-Trak with programming like the multi-trak. While keys have the same design the keyboards have a different interconnect. The one I got has some tears in the panel membrane switches. I've developed a technique for repairing these. Use a contact adhesive that stays flexible and douse some THIN slices of polyfoam or like that with it too and lay it over at the appropriate moment of dryness. You can strategically build and mend breaks and tears in that stuff.
     By this time manufacturing was pretty good and power draw low so you probably won't see many power supply problems or chips dying aside from the CEM3394 possibly being the most congested analog component. But I've only seen one fail to date in machines I'm working on I think. I did see a failed 4174 chip and apparently a 4503 also that measured good... but when I replaced it at least all the notes played. I thought initially there would be some bad voice chips but as it turned out once those were replaced the TUNE routine started actually getting good data. I initially thought the 8253 was bad because pin 17 had nothing. I replaced it and then saw some intermittent looking signal there. But the VCO's were still tuning all the way down to subsonic :-). Made some interesting noises though after replacing the 4503 which I thought might be tampering with the signal there. By the way this synth DOES NOT share the lovely 'bug' in the Multi-Trak where you have to load patches when the battery dies before it will even allow you to program patches and get a real sound out. I was unable to get patches to load from the .wav file..probably because of the bad chip also. But when I sent the midi dump to it after Record/4 (noted on the panel. enables midi it says..) it took them right in! The factory dump though is odd in that there are some really weak levels and very loud ones on others..and a few totally missing patches. As though someone didn't quite finish them? I have my own bank up on .wav but have completed a factory mod to deal with some of these issues also. Serial 2560 I think this last one was from Phoenix.
      7/15 I got a return of one that arrived w/ pitch wheel out of calibration. I'd assumed maybe it was done like other sci mid 80's synths but no result. I thought from his description there was an actual pot defect but I got it back and saw that voltages were normal sweeping both directions but only pitch movement was heard in upper half and the synth was out of tune. Of course it does a tune calibration on boot but apparently not a wheel calibration. I FOUND through experimenting that this is done by holding record and pressing the top row button for the programming matrix! All better! Meanwhile, here is the MIDI expand summary:

After hitting RECORD then while holding 5 to initiate the midi expand 'menu'...

  1-  Selects MIDI mode 1 (OMNI on/poly). If the instrument is in SPLIT mode, data from the MIDI in port will be passed to both programs (as though the synth were in DOUBLE mode). This is the reverse of using button 3, below.
  2-  Initiates a 2,240 byte system exclusive dump consisting of patch data. The LED for PROGRAM SELECT 2 remains lit during the few seconds that this takes.
  3-  Selects MIDI mode 3 (OMNI off/poly). This is the reverse of using button 1, above.
  4-  Not used.
  5-  Toggles between enable and disable of program changes. Transmission and reception of program changes via MIDI is disabled by default when the synthesizer is switched on.
  6-  Toggles between enable and disable of both the pitch-bend and modulation wheels. On power-up, MIDI transmission and reception for both is disabled by default.

I have lots of parts for these synths save the dac I think and voice chips I only keep enough for my repairs
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