Circuit Overview:
A DK600 analog board with digital interface and 73 timbric programs and 55 patches for use in 'midi controller' mode. In fact Nate Holloway has been so kind as to provide Service Photos inside the DK700. The "E" (which has an unused i/c for last 6 pins; from expander layout I think) and "F" interconnect are ommitted. "H" formerly the keyboard i/c, now goes to a second cpu board on the right under keys and keyboard goes to it instead. Only pin 7 and 10 of "H" are used for a serial xmit and receive line between the dk600 mainboard cpu and the NEC D7810G cpu on the new cpu board. Also there is only one EPROM socket IC6 on mainboard which obviously omits code for key scanning and button scanning; now handled by 27C64 on other board called "Micro". This board has SRAM 2kx8 ram also and Li battery for the sequencer and midi controller that wasn't present on DK600. Weird they actually downgraded the number of synth patches, but it's a consequence I suppose of adding another few bytes per patch on the S+H feature, which I assume is software generated in new eprom code on dk600 cpu board! I see code is done by Roberto Giobbi. I'll upload when i can.
Service Tips:
Battery issues are still common. [And oh if you lost memory eg. octave may say '2', but instead fo1/fo2 are set to point 4051 at X2 (grounded). You must toggle the value to get any clock to tms3631 chips.] One is a Li cell on the 'micro' board so not a service issue in terms of potential leaks at least. Just refer to DK600 page for more tips since 99% of issues will be same, noting exceptions in circuit overview. Also note broken pins 17 + 18 on "C" connector which are wired back to pin 13 + 4 accordingly on IC26. There are .01uf caps if you follow the traces to other side of board to each of those lines, whose other legs tie together to a line back to pin 15 of the "C" connector. I worked on one that had analog board issues someone else had built a daughter board with ic16 and a dallas memory voltage control ic and a Li cell. Just cleaned some trimmers and it worked! The second one i had to deal w/ cleaning the board up w/baking soda and replacing ic12 which probably got cracked in previous amateur attempt? Then the usual connection to pin 12 of ic16 and a couple other traces under it burned.
Parts:
I have several scraps from Siel units and lots of the discrete parts. Check Sander's site for a guy who has made RAM cards for these also if you need that.
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