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KORG 800DV (Maxi-Korg)
MODS - Rear Panel & Sockets, Proper CV/Gate Inputs

| Synth Index | Korg 800DV | 800DV Mods1 | 800DV Mods2 |

| IEC Main Sockets | Additional Sockets | Proper CV/Gate Input |

IEC Mains Socket
The 800DV came with a little compartment at the back to hold its power cable & power plug. It's quite neat, but it's still a flying lead.... so I added an IEC Mains Socket and removed the original flying lead. The lead compartment is now empty....

I placed the IEC mains socket in the middle because that's quite near to the power supply board. Disaster did happen to me while drilling on the rear panel - the PSU board is directly located behind, and I think i accidentally bent a transistor, and in the end caused it to short out a fuse. I could've removed the PSU board before doing anything to the rear, but hell, you'd then have to remove the top panel , keyboard, the frame holding the front panel, plus a lot of other things before you can remove the PSU board.... the metal frame design of the 800DV made it quite difficult to access anything at the back....

To make the IEC Mains Inlet hole, I use a screwing hand tool, which is an M10 Radius Hand Hole Cutter, 28x21mm (
RS Cat.#543-614 or or 541-501), with matching 10A Snap In PCB Mount IEC 320 Plug Socket (311-8031 or 488-191).
As I knew i was gonna add CV/Gate and there are 2 sets (Upper / Lower), plus 4 Aux CV's for the 2 travelers, ie, HPF (Upper) / LPF (Upper), HPF (Lower), LPF (Lower), I actually drilled and made 10 holes for sockets (plus one for MIDI for future use!)



Proper External CV/Gate In
The 800DV CV/Gate sockets that Analogue Solution provide, would require holding down 1 key on the keyboard to work. This is actually due to the S&H Gate Circuit of the 800DV, which needs -V (-10V) at KEY OFF, and Open at KEY ON. If this voltage change is not given to that part of the circuit, the trigger/gate will not work.

The Japanese E-Lab site has all the info and the proper CV/Gate Mods Schematics on the 800DV (site in Japanese).
[I don't fully understand Japanese, but can read certain chinese characters that Japanese uses and also I do know a fair amount of the "English" characters in Japanese symbols, so I could roughly understand the info on the site. Also, info on the schematics are given in english.]

The circuit/schematic that he provides, also incorporates a CV Tuner, which is very useful!

I used the OP-07 op-amp instead of having to use a stepdown voltage regulator (as the 800DV operates at 20V, but most op-amps' max supply voltages are < 15V) and built the circuit on stripboards...
I dun do custom made PCBs, so I convert everything into stripboard. It's nice, and everyone without PCB making equipment could do it.

Stripboard for SINGLE CV/Gate (Need 2 of these)
Korg 800DV CV-Gate Stripboard
Click to Enlarge

Combined Stripboard for Dual CV/Gate
Korg 800DV CV-Gate Stripboard Dual
Click to Enlarge

Took me a while in getting this to work, because initially, i got one of the transistors pin-out wrong, because the information on a datasheet i found on the web was wrongly labelled... bugger!
A lot of care has to be taken when wiring this up.
One main problem was the Internal / External CV/Gate switch.

There are 7 things to switch/swap
- CV (U) / CV (L) / Gate (U) / Gate (L) / S&H Gate (U) / S&H Gate (L) / Repeat Gate

I actually had to use one 4-pole DPDT switch and one 3-pole DPDT switch.

I also configured the CV/gate In Jack Sockets to switch between linking Upper/Lower - ie the Upper CV/Gate is wired and routed to the Lower CV/Gate socket until a jack is inserted and breaks this connection. this way, I can use just 1 set of CV/Gate and control both Upper/Lower voices as dual voice but also have the option of plugging in a 2nd CV/Gate if I want split operation.
Mounted the board next to the PSU board, just under the CV/Gate In sockets:

Connectors are used, and I have an extra board with just the CV Tuner Trimmers, mounted on top of the REPEAT/RING MOD PCB:

This E-Lab circuit is actually very good - as all the functions like Bender, Portamento, Repeat would work for he external CV/Gate Inputs.



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