Korg Poly800/EX800 Users

I've checked it with the multimeter now and the pin 9 and 8 on the
80C85 show 5v DC.. it doesn't respond to setting any parameters or
the keys, just stays at this noisy sound after the initial
filter/frequency sweep

any ideas?

Thanks!
jouni



--- In korgpolyex@yahoogroups.com, Michael Hawkins
<korgpolyex800@...> wrote:

>
> If you have an oscilloscope or multimeter then download the

schematics from our group web site and then check the test points
that are shown on the schematic.

>
> If you have an oscilloscope then you can check the waveforms

precisely. If you only have a multimeter then looking for some
voltage will do.

>
> Disclaimer: Just be very careful poking around because you don't

want to short anything out and do more damage than you already might
have.

>
> Regardless of the condition of the display chips, the display won't

show anything at all if the RES6.5 clock is not running. So check for
voltage on pin 9 of the 80C85. It should read a little above 0 volts.

>
> Let us know what you find.
>
> Mike.
>
> dharmaone1977 <dharmaone1977@...>

wrote: I've got exactly the same
problem!!!

>
> got my poly800 mkI 2nd hand, LED display/keys not working, the only
> thing it gives is a slow sweep from sub bass to high freq noise a

few

> secs after turning it on, then stays making noise until i turn it

off.

> chorus, filters and oscillators hence work.
>
> Any ideas?
>
> When powered the IC's all seem to have a voltage across them apart
> from the LED IC. could it be a broken IC or (hopefully) something

in

> the +-5V power circuit not giving the board proper juice? the

voltage

> regulators maybe?
>
> It's not mkII so it doesn't have internal battery.
>
> No signs of leaked caps or cold solder joints or physical damage...
> Tested with both batteries and 9V adapter
>
> THANKS!!
>
> Jouni
>
> --- In korgpolyex@yahoogroups.com, "Rob" <r.bowe@> wrote:
> >
> > Well, the Poly-800 I saved from the dumpster is not looking too

good

> > at the moment! The bad news is that it has no LED read-out of any
> > kind, no flashing, nada. The good thing is, is that as I checked

the

> > V+ at the input I caught it dropping a few volts and suspected

some

> > kind of life! I proceeded to connect a set of phones to it and

lo and

> > behold, the unit gave me a real slow, but sweet pitch, amplitude
> > and filter sweep, in stereo several seconds after start-up! It

all

> > swept up to a max and held. The only thing I can do to the sound

is

> > tune it with the slider and turn it up and down with the volume

pot.

> > Absolutely nothing else works. (I can affect the res. and cut-

off with

> > VR's 2 & 3) So obviously the power, amp, filter and oscillator

(not

> > necessarily in that order!)sections are working fine. Is there a
> > secret button combo or power-up trick that would re-initialize

this

> > thing or is the back-up and sysex "lost"? The lack of display is

a

> bother.
> > As you may remember from my previous post, I am a fairly

effective

> > bench tech and a damn good solderer and I read schematics fine,

so

> > even if there is something wrong at the component level, I

shouldn't

> > have any problems doing the fix, as long as someone out there

has seen

> > this problem before and knows the situation here. Aside from

some one

> > familiar with this glitch, it will be a stretch. Hopefully it

won't be

> > a big deal, so if you have an idea, I'll try to raise another

Korg

> > back from the dead! Otherwise, I have a really huge mono-patch,

single

> > sweep noise machine.
> > I am sure that's why I got this for nothing! But in the words of
> > Monty Python...
> > "IT"S NOT DEAD YET!!"
> >
>
>
>
>
>
>
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