Circuit Overview:
The DS-2 is an enhancement of DS-1 with extra LFO and a polyphonic string divide down synth. First synths I know of to have what are labelled "DCO's". I now own a DS-1 which is quite rare I'm told. All serial numbers I've seen have been double digit save one that was 120 something I think. On the DS-1 there's a wire from each key interfaced to a mother board on the left as you see in the internal photo. The cards on that have mostly common digital chips (40xx, 45xx, and 74LSxxx and so on) and a few op amps. Along with some 4016 analog switch chips. SO I assume they are doing some kind of waveform generation over here. Then there is an analog board with 4 or so 3080 OTA's and a couple 3086 transistor arrays and a dual transistor down on the bottom middle. And some other sub boards here and there and some up with the controls. Overall it's a fairly straightforward analog subtractive synth in architecture but some unconventional looking approach in the digital circuitry.
Service Tips:
Ok, first my unit had an error. Well make that two errors that were the same. They did not put any pull down resistors on the "Sawtooth" (labelled SEGA in diagram) lines from the switches. Dark grey and red wires. You may add 100K resistors to ground whereever it is convenient to keep the thing from delaying 10 seconds when you switch say from saw to triangle wave..and then going though this phase where the noise combined with the 4069 chips logic threshold just switches back and forth between the two waves rapidly! I can't believe they released the synth that way!
OTherwise, the DS-1 is really built fairly well. No bad interconnects like in my performer. But I did have to clean some shellac looking stuff off some of the pins in the cards that have pin row interconnects. And all chips are socketed and pins on some of them tend to get black build up on them. A thorough cleaning and I had a working synth mostly! They use the type of sockets where it's easy to misallign a chip from front to back so that pins don't quite touch the contacts in the sockets. Watch out as you clean them. SOLDER JOB IS EXCELLENT in mine. LOts of hard wiring but all kept out of the way. A joy to work on compared to many synths. TO ACCESS, simply pull the two side screws and the three that are right behind the keys on the front panel. Do NOT pull the ones that go into the wood! The whole front with the wood sides hinges up for nice access! Then there are two screws underneath that allow you to pull the keyboard up. Don't pull up on the keys. Often they'll come loose as the glue is getting old and brittle. But goop adhesive works great to hold them down again if you have problems.
OH and another problem with my DS-1 was that the 1458 failed which is located on the D/A board. That caused the thing to just latch the first note hit when glide is on and basically remove keyboard control somehow. Anyway, just a heads up in case you see that problem.
CARD LOCATIONS:(this will save you a ton of time with schematics in hand. Some schemos seem to be marked as though they are two VERSIONs. This is not the case. First "Version" is analog stuff. hehe.)
DWG (Drawing...) 6- EG's. 2 ea. of this circuit on board attached to slider board. (error on 4016.
Pin 3 should be pin2 going to ground! Also a fixed resistor is attached to real pin 3 in series with release pot. Attack is upper center. Decay pot to the right and 5K one is sustain.)
DWG9 - LFO. Fc is apparently the frequency control. Don't bother looking for waveform switch dwg.
DWG3 - Filter, source mixer. LOcated on main board, bottom center.
DWG4 - VCA, output. Also located on main board. My output amp marked 1458, right rear most.
DWG11- LFO delay. This is the little boards that stand off from the main board by card cage.
DWG13- Noise generator. This is under the key movement. Remove bottom two screws and tilt keys up.
DWG14- Power supply. 4 screws hold down shield. Reseat chip while you're in there.
SCHEMA-A -Keyboard coder. Slot 7 (rearmost in card cage)
SCHEMA-B -Code conversion Slot 6
SCHEMA-C -DCO's. Slot 2. Transistors BC286 on mine.
SCHEMA-D -Digital Mult. - Slot 3 and Slot 4 (two identical boards both drawn on this schemo)
SCHEMA-E1, E2- Waveform Generation. Back center of unit with interconnected board. That's where I chose to add my 100K resistors noted above. Be sure to verify you have the right red and dark grey wires.
SCHEMA-F -DAC. SLot 5. BC308B transistors in mine not 208, and BC1738 by "K" lower right. K goes to code conversion board btw.
Slot 1 contains a card with just connections coming in from glide pot, etc. And some filter caps.
INFORMATION SPECIFIC TO DS-2 (but mostly identical to DS-1 above it appears):
Here is a listing of board locations/schematic labels from Giovanni Mocerino! Thanks!
P-431 Keyboard coder (schema A - slot 7)
P-432 Code converter (schema B - slot 6)
P-433 DAC converter (schema F - slot 5)
P-434 Digital mult. (schema D - slot 3 and 4)
P-435 Master oscillators (schema C - slot 2)
P-436 Waveform generators (schema E1, E2)
Also be forewarned that the digital stuff is NOT INCLUDED in the service manual I have! Giovanni also drew out the P-431 section nicely and I'll make a shrunken/nicely readable copy of it available for download here!
Parts:
Lots of discrete parts but some oddball ones. Ask if you need a specific part. I'd like to find a source for the odd slider caps. I had to take some off my performer to finish this one.
Contact
