Siel DK-80 -1985    Weight= 18 Lbs.w/psu Number Manufactured = 1500? MRP = $995


User Manual: Sander's Site
Reset Proceedures: N/A
Operating System code: dk80a.bin and dk80b.bin
MIDI or other control protocol:
Software related Links: N/A
Patches or knob settings:
Circuit Overview: below
Scematics/Service Manual: Sander's Site
Common Service Issues/Tips: below
Parts Sources: Keys knobs semiconductors misc
Uncommon chips/modules used: M112B1 sound chip pdf available, SSM2045 VCF/combo, SSM2031 HFO, TDA1022 bbd
Modifications:
General Info Links: Vintage Synth Explorer or Synthcheck review (1985) in pdf or Polynomial EX80





Circuit Overview:
     An organization of 2- DK70 architectures, save they only used 6 voices per chipset! Makes one wonder...but SSM2031 HFO supplies signal to M112B1 sound chips which creates all waveforms to be modified through SSM2045 combo chip controlled by the digital interface. There are two channels of this operation on the DK-80 and it gets a 'Bi-timbral" label. An interesting synth capable of some fairly cool sounds that have enough analog character to make it worthwhile and enough digital complexity to make it different from most. UNFORTUNATELY one real let down is you can't send BENDER messages to it! This is because, of course, there is direct analog control of the HF oscillators so there is no facility for genearating pitch modulations from the computer. Only envelopes for Filter and VCA functions on this one. (The VCA's are first inside the M112B1 chips. S+H cells provide analog control voltages for them as set through the DAC and multiplexers) No portamento again for the same reason. All notes are generated in the M112B1 chips using standard organ technology so there are only two ways to vary pitch at the two SSM2031 hf oscillator control inputs. The computer sends data to be converted by the DAC and stored on S+H cells for the 2 VCF's, VCA's and LFO's which then can be set to modulate the HF oscillators or not. FUnctions 95 and 96 appear to be undocumented functions in the editing also. I'll try to study this more some day. They could have set it to at least operate the switch for lfo at value of 64 or like that with the mod I guess. But they were pretty 'bare bones' in their implementations on that kind of thing. You can select footswitch function. :-).


Service Tips:
     BEWARE: Strange things happen when you plug a 1/4" mono into the headphone instead of a/b outs. Caused me much pain one night. SOME patches would put out a very weak noisy tone... and it would get normal level when you turn on BOTH chorus lines! (parameter 81).

Mine had some power supply issues. Blown diodes...can't recall what else. I installed a standard AC cord socket and transformer on mine since it didn't come with a supply. Barely fit but makes the thing a little more portable. Now if I can just find a decent key movement for it :). Ohhh never mind. I got a scrap DK600 in so I busted off three of the key bushings and plastic welded the pieces on to the messed up DK80 movement, and warped the metal and got it all straight again. hehe. So it's whole once more. On the DK70 which is Identical in many ways I've seen the M112B1 fail and also the op amp that buffers the DAC output.




Additionally I'd note that we've only seen serial numbers up to 1445 so far. If anyone has higher numbers let me know so we can narrow the field on how many were made. I'd had only a couple in the 600's before that. Parts:
I have found a source for the M112B1 that isn't 100 dollar minimum if maintains his stock. Ask. A guy is making cards for them now and see Sander's site for that info.
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