Korg Poly800/EX800 Users

Hi you all, maybe someone could lend a hand here.

    I have an old EX-800 which I want to revive. It was connected to a 220V 
mains, blowing something inside. I got it already messed, but not that much. 
Seems 3 transistors were changed, and a zener. But the transistors are not 
original and the zener is unreadable. Also, the only schematic I got access 
is incomplete and very hard to read.

    So, if anyone is willing to open up his/her gear and take a look, I 
need:
    - What zener is D4? Can you read the tension between its legs?
    - What tr is Q4? Is it really inverted on the board?
    - Taking a look at schematic, what are the tensions on the points A 
(should be +5), D (should be +5), 6-7m 6-8A (should be -5V), 6-9A
    - Is there any documented mod for changing the internal power supply for 
a +/- 5V one (I think there is also 12V)?

    Thanks!
    Alexandre

Uhu! Got it working!!!!!!!!!!!!! :oD

    Totally bypassed the internal power supply. The schematic is a mess and 
I didn't want to spend an entire night trying to calculate values for the 
parts.

    The poly works with +5, -5, +9 volts. The +9 goes to the analog output. 
Put a PC power supply and it is working.

    I'll write a tutorial up of how to do that, and identifying some 
tensions on the schematic. Mike, I'd be glad if you put it on your site.

    Now I have an EX-800 :) Only one button is broken (start/stop sequencer) 
but I think I gotta many things to foul up here heheheheh

    Greetings from Brazil
    Alexandre

Amazing work.  Too bad that button is actually a fun one. On Thu, Jan 8, 2009 at 9:35 PM, Alexandre Souza 

> Amazing work.  Too bad that button is actually a fun one.

    Thanks! But all my buttons are acting up. They need to be very hard 
pressed to work and some don't work at all. I think I'll have to disassemble 
them and clean. It will be a pain in...well, you know where.

    Now I'll build a small power supply to put inside the chassis. And do 
the 3-trim-pot mod. later I'll try to fix the buttons. If someone has a 
spare button to put here (and a new top cover would help a lot, mine is very 
corroded he he he) I'd thank a lot.

    Anything else fun to do before I close the cover?

    Greetz,
    Alexandre
    PS: photos in 5 minutes in http://tabajara-labs.blogspot.com

>    PS: photos in 5 minutes in http://tabajara-labs.blogspot.com

    Done. Feel free to take a look and comment. As soon as possible I'll
make a complete tutorial in PDF, also incluiding all mods I can do on this
bestie :o)

    BTW: Something I never tried:

    Taking a look at the keyboard scanning matrix of the Poly-800, seems 
that there are space for 7 more keys :)

    Who knows what can be done there? :o)

On Fri, 2009-01-09 at 01:48 -0200, Alexandre Souza wrote:
> > Amazing work.  Too bad that button is actually a fun one.
> 
>     Thanks! But all my buttons are acting up. They need to be very hard 
> pressed to work and some don't work at all. I think I'll have to disassemble 
> them and clean. It will be a pain in...well, you know where.

You can buy big bags of clicky switches from eBay.  It's worth just
replacing them - there's nothing you can really clean.

Gordon