Korg Poly800/EX800 Users

From: zwright88@... [korgpolyex] 
Sent: Thursday, July 26, 2018 2:33 PM
To: korgpolyex@yahoogroups.com 
Subject: [korgpolyex] Strange 800 problem: locked up, display error

  

Hi folks,




I have a Poly 800 mk1 that has developed an odd problem. 




Upon switching it on, the display reads "1.7 50 01", no sound is able to be produced other than the occasional low frequency click, and none of the buttons are responsive at all. Playing keys will oddly make the value number displayed gradually increase, but the first two numbers remain at "1.7 50"




I'm not able to attempt to re-write the patches from tape since buttons and rear switches are unresponsive, so guessing this is a more serious problem. 



Anyone experienced this before? I found only one mention of someone with the same problem online, but there was no answer. Thanks!

> This is the only sound it sometimes makes, but only does so by
> intermittently, when pressing keys quickly:
> 
> 
> https://soundcloud.com/dkon/poly800problem/s-vEWHY
> 
>

 Subject: Re: [korgpolyex] Strange 800 problem: locked up, display error
 To: korgpolyex@...m
 Received: Friday, July 27, 2018, 7:56 AM
 
 
  
 
 
 
   
 
 
     
       
       
       
 
 
 
 
 
 
  
 Most likely, the problem is with the sequencer
 enable switch or with IC33 or IC34.
 I would start by checking the switch
 using a multimeter. If it is not the switch itself, then
 replace IC33. If that does not fix it, then replace
 IC34.
 /Mike
 
 On Thu,
 2018-07-26 at 22:59 +0000, zwright88@... [korgpolyex]
 wrote:
  
 
 
 
     
       
       
       This is the only sound it sometimes makes, but only
 does so by intermittently, when pressing keys
 quickly:
 https://soundcloud.com/dkon/poly800problem/s-vEWHY
 
 
 
     
      
 
     
 
 
 
 
 
 
 
 
 
     
      
 
     
     
 
 
 
 #yiv0616266308 #yiv0616266308 --

> Yes, no programming required; just swap the chips.
> 
> In case you'd rather order them locally: TC40H is the equivalent to
> 74HC.
> So you can also use a 74HC240 and 74HC138 instead.
> 
>

> And I would not order them from eBay. Better to get them from a reputable
> supplier that is guaranteed to send you working units.
>
> /Mike

From: zwright88@... [korgpolyex] 
Sent: Friday, July 27, 2018 8:08 PM
To: korgpolyex@yahoogroups.com 
Subject: [korgpolyex] Re: Strange 800 problem: locked up, display error

  
Thanks for all the great info, all. Would these two ICs do the trick? 


https://www.digikey.com/short/jr3mnm


https://www.digikey.com/short/jr3mnt

> Hi all, I have an update and a new question:
> 
> 
> I replaced IC33, and the original issue with my 800 being completely
> unresponsive seems to be fixed! However, new problems have appeared.
> 
> It's currently behaving like it needs the factory patches re-written: 
> the patches are playing low clicks and white noise. However, the tape
> write switch doesn't do anything - flipping it to "enable" doesn't
> make "TAPE" appear like it should, so it's impossible to put it into
> tape write mode.
> 
> Also, the button "3" seems to be unresponsive, as well as a couple of
> the keys. No idea if this is related to the other issues or not.
> 
> Any ideas on where to go fro m here? Would IC34 possibly be a culprit
> or is there something else that may need replacing? I still don't
> think it's an issue with the switch itself as there's no visible
> corrosion and I'd never had that issue in the past.
> 
> Thanks again, this group is an incredible resource!
>

> Hi Mike, thanks for the reply.
> 
> 
> I just replaced IC34, but unfortunately the problem is still there
> with the "3" button and the tape switch not working.
> 
> Any other ideas about what to look at? Or is there a way I can narrow
> down the issue with a multimeter?
> 
> I did also just do the internal battery mod (mine was a mk1 with no
> 2032 present), and that is working great now.
> 
> Thanks again!
>

 Subject: Re: [korgpolyex] Re: Strange 800 problem: locked up, display error
 To: korgpolyex@yahoogroups.com
 Received: Sunday, September 30, 2018, 1:13 AM
 
 
  
 
 
 
   
 
 
     
       
       
       Quite frankly that's a bit beyond my ability
 level - I have the schematics but no idea what to look for
 there.
 
     
      
 
     
     
 
           
   
  
 
     
      
 
     
         
         Posted by: zwright88@...

> Quite frankly that's a bit beyond my ability level - I have the
> schematics but no idea what to look for there.
> 
>