Korg Poly800/EX800 Users

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
>  
>  
>      
>                        
> 
>  __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around 
> http://mail.yahoo.com
>