Korg Poly800/EX800 Users

Willi,

sorry for the delay, I've been looking for this:

http://synthetizer-sche.chez-alice.fr/korg/poly800/poly800-2.html

This is a simple starting point to calibrate the power supply and
check a couple of other points on the board.

Most of it applies to Poly 800 MK 1 and 2.

Mike.



--- In korgpolyex@yahoogroups.com, "earth2willi" <earth2willi@...> wrote:
>
> Hi Mike
> 
> Thanks for the reply.  I do have a multimeter.  I didn't see any
signs of corrosion /
> deposits/breaks on either side of the analog or digital boards, but
I didn't check both 
> sides of the buttons/LED PCB.  I'll take that board out and check
both sides, although that 
> seems an unlikely candidate given the display and buttons work OK. 
Still, I will give it 
> another look.  What should I try with the multimeter?
> 
> 
> Thanks again!
> willi
> 
> --- In korgpolyex@yahoogroups.com, Michael Hawkins <korgpolyex800@>
wrote:
> >
> > Hi Willi,
> > 
> > The fact that you can do a tape dump and get the "Good" message
virtually proves that 
> your ROM, RAM, CPU and CPU clock are OK. And because you can command
the Poly via 
> the rear switches and get that tape load working, emphasizes how
much I doubt you have 
> a corrupted ROM.
> > 
> > I've not heard of anyone damaging their Poly's using a bad audio
cable either.
> > 
> > My first guess is that you probably do have some damage on the
circuit board from a 
> little battery acid combined with rain water. I would obtain a
strong magnifying glass and 
> then, sitting under a bright light, thoroughly examine the entire
board looking for any 
> signs of corrosion. Any white salty looking deposit is a prime
candidate. If you've 
> previously used a brush or fingers to rub off any salty looking
deposit then try to 
> remember where it/they were and thoroughly examine the copper tracks
for breaks. The 
> copper tracks are under a solder mask which is the green color on
the board so it can be 
> quite difficult to find a crack but the green coating is also what
makes the boards so well 
> protected from general corrosion.
> > 
> > You might also have an intermittent circuit break. This could take
a bit more time to nail 
> down.
> > 
> > If you have a multimeter then we can do some more testing. Let me
know if you have 
> one.
> > 
> > Mike.
> > 
> > 
> > earth2willi <earth2willi@> wrote:                                  Hi
> >  
> >  I'm the original owner of my Poly800 mk1.  It was my first synth!
 It's in pretty good 
> >  physical shape overall, but unfortunately it has seen better
days.  There seem to be 
> some 
> >  very knowledgable people in this usergroup, so here is my situation.
> >  
> >  Short; it's not making any sound, when it occasionally does make
some noise on it's 
> own 
> >  it's distorted as if the presets are corrupt and the sound does
not always reflect any 
> input 
> >  played on the local keyboard, and the MIDI has stopped outputting
data.
> >  
> >  My Poly800 worked great for many years.  It saw some outdoor use
when I was in 
> >  highschool marching band; once when we traveled to Canada to
perform, I forgot my 
> >  keytar strap, so we ended up duct taping the keyboard to my band
uniform.  When we 
> >  marched, it rained, and the Poly800 did get a bit wet but not too
bad.  It worked fine 
> for 
> >  many years after that.
> >  
> >  I also had some alkaline batteries in it that I forgot about and
they leaked, but the 
> leakage 
> >  does not seem to have traveled outside the battery compartment. 
Inside the keyboard 
> was 
> >  a bit dusty but there is no visible corrosion (a common problem
in Hawaii, where the 
> >  keyboard (and myself) had been living the past years).  I cleaned
out the insides with 
> some 
> >  compressed air but that hasn't solved my problem.
> >  
> >  I'm not sure what exactly is wrong as they keyboard appears to be
functioning OK 
> (powers 
> >  up, can hear the headphone jack amplifier power up (just the
click of it being powered 
> up, 
> >  no excess noise), and when I attempt to flash it using a .WAV
file of the original casette 
> >  data it says 'GOOD'.
> >  
> >  However, the keyboard does not trigger the sound.  Usually there
is no sound, but 
> >  sometimes there is some spurious random output, like the DCO or
VCF or something is 
> >  getting a corrupt/random 'preset' and the VCA is not usually
responding to keyboard 
> >  input.  It will sometimes audibly respond to the keyboard input,
but the sound will be 
> >  accompanied by the noise generator going crazy or some random DCO
output.  Then 
> the 
> >  sound will all stop and cut out suddenly.  It usually won't make
any more noise or 
> respond 
> >  to the keyboard at all again, until I put it away and try again
some other time.
> >  
> >  The sequencer does advance per each note, and on the occasional
output that does 
> >  respond the keybed/DCO's will seem to track accurately, so I
don't think it's a problem 
> >  with the keybed itself.
> >  
> >  I was just using it as a MIDI controller until that stopped
sending any data, which lead 
> to 
> >  my discovery of the audio problem.  :(
> >  
> >  I've tried flashing it a number of times, with all the write
switches enabled (and in 
> various 
> >  permutations; e.g. just program data).  I've used a couple
different .WAV files.  The unit 
> >  claims to get a 'GOOD' flash.  I had some trouble flashing it
when I was trying to check 
> up 
> >  on the MIDI and battery situation a while ago due to a bad cable,
and then the audio 
> >  problems started up.  So I don't know if they are related or if
that is possible.  It almost 
> >  seems like the OS (or ROM or CPU) are corrupt and it can't
properly load/play the 
> presets.  
> >  I haven't tried sending the data over MIDI sysex but again the
MIDI out is buggered...
> >  
> >  It seems unlikely the ROM is corrupt, but is there any easy way
to test the ROM or CPU?  
> Is 
> >  it possible to get these parts anymore without cannibalizing
another Poly800?  Do these 
> >  seem likely candidates or should I be investigating some other
areas first?  I have a 
> simple 
> >  multimeter but not an oscilliscope...
> >  
> >  Sorry to ramble but I've tried to be complete with the
information related to the 
> problem.  
> >  Please let me know if there are any questions or suggestions. 
And thank you very much 
> >  for your time.
> >  
> >  Sincerely,
> >  willi
> >  http://www.earth2willi.com
> >  
> >  
> >      
> >                        
> > 
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