Korg Poly800/EX800 Users

Hi there!

Got a multimeter and downloaded the schematics - will check the CPU
pin 9 later tonight. How are the test points shown, I might be stupid
but I can't see them on the schematic?

here's a couple of shots of the board -
http://www.mixtapedealers.co.uk/korgpcb2.jpg

and

http://www.mixtapedealers.co.uk/korgpcb.jpg
showing a bit of corrosion some of the power section solder joints

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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