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 <alexandre-listas@...> wrote:

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.

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