Archive of the former Yahoo!Groups mailing list: Korg Poly800/EX800 Users

I don’t think you would even see D1 on 596-8. It’s a zener diode that supplies power to the memory chip from the 6 C-cells when power is turned off. Since I believe version 8 had a factory installed CR2032 lithium cell between IC18 and IC 19 for memory backup, I think D1 and R1 were removed from the board. I don’t think I’ve ever seen a version 4. I saw a version 7 that had solder pads in the location where the lithium cell would eventually go, but no battery. It still had D1 and R1 on the board and they would have to be removed if you wanted to solder in your own battery. If they were not removed, the C-cells would attempt to recharge a non-rechargable lithium cell. Not a good idea. I have an old version 2 that has no solder pads for a battery, no room for the battery and no indication that they had thought about that yet. I think the only schematic available is for the old boards that include D1 and R1. I think D2 is just the “crowbar” diode to protect the voltage regulator circuits in case someone plugs in an AC adapter with center pin positive instead of center pin negative. It is regularly the first thing to burn up if you plug in the wrong adapter.

 

D1 is a 250mw (1/4 watt) zener, 4.8-5.3 volts. Any zener around 5v and at least 250mw should be good here.

D2 looks like a general purpose 1A rectifier

 

Don Backshall