Korg Poly800/EX800 Users

Stop me if you've heard this one before...Bought an "As Is" Poly on
eBay. Cleaned it up, plugged it in a lo and behold no display. Sound
is present at the headphone jack about 30 seconds after turning on.
It's a frequency sweep from low to high (sounds almost like the whoosh
of a jet engine starting) followed by constant white noise. This sound
is affected by turning VR1, VR2 and VR3 trimpots.

I'm okay at basic electronic troubleshooting and repair, but have run
out of ideas, so wondering if anyone has had a similar experience. I
have pretty much determined it is not a power supply circuit issue (as
I was hoping when I bought it). All the IC's I sampled are getting
correct power. Also on connector KLM596 CN6A, Pin 6 shows 4.98v, Pin 8
shows -5.07v and Pin 9 shows 9.44v, all of which I believe to be
normal and show the power section is working OK.

Unfortunately, I do not have access to a scope. Is it even worth going
any further at this point without one? In a previous post where
someone had a similar issue, it was mentioned that if the RES6.5 clock
was not running this could cause a dead display. I did check RES
5.5,6.5 and 7.5 pins on M80C85A chip. RES7.5 pin shows 1.45v, but the
other two are 0v or at least < 1 mv.

Any ideas or suggestions on where to look next?

Have you tried sending a SYSX dump of the original patches to the
Poly? I have found MANY a poly\ex that were sold at garage sales and
thrift stores because no-one could figure out why they didn't hear any
sound, or only heard noise and blips. After a Sysx dump, 8 times out
of 10 it'll fix the problem...

The poly's memory is battery backup, so there is decay after years of
no-use and makes the patches corrupt.

Erik


--- In korgpolyex@yahoogroups.com, "selloutdesigns" <aah_public@...>
wrote:

>
> Stop me if you've heard this one before...Bought an "As Is" Poly on
> eBay. Cleaned it up, plugged it in a lo and behold no display. Sound
> is present at the headphone jack about 30 seconds after turning on.
> It's a frequency sweep from low to high (sounds almost like the whoosh
> of a jet engine starting) followed by constant white noise. This sound
> is affected by turning VR1, VR2 and VR3 trimpots.
> 
> I'm okay at basic electronic troubleshooting and repair, but have run
> out of ideas, so wondering if anyone has had a similar experience. I
> have pretty much determined it is not a power supply circuit issue (as
> I was hoping when I bought it). All the IC's I sampled are getting
> correct power. Also on connector KLM596 CN6A, Pin 6 shows 4.98v, Pin 8
> shows -5.07v and Pin 9 shows 9.44v, all of which I believe to be
> normal and show the power section is working OK.
> 
> Unfortunately, I do not have access to a scope. Is it even worth going
> any further at this point without one? In a previous post where
> someone had a similar issue, it was mentioned that if the RES6.5 clock
> was not running this could cause a dead display. I did check RES
> 5.5,6.5 and 7.5 pins on M80C85A chip. RES7.5 pin shows 1.45v, but the
> other two are 0v or at least < 1 mv.
> 
> Any ideas or suggestions on where to look next?
>

I didn't try sysex (don't think the stock Poly 800 1 has any sysex
capability), but I did try loading up the factory patches via the
cassette interface. I had to do it blind though since the display is
dead and it did not appear to have done anything. I believe that the
input switches are also dead as they are on the same board as the
display LED's. I also tried blindly adding a manual patch, but no luck
there either. I may try at least hooking up the Midi side anyway to
see if at least the Midi In/Out is responding.

<<aaRoN>>

--- In korgpolyex@yahoogroups.com, "Erik Hines" <sablerock@...> wrote:

>
> Have you tried sending a SYSX dump of the original patches to the
> Poly? I have found MANY a poly\ex that were sold at garage sales and
> thrift stores because no-one could figure out why they didn't hear any
> sound, or only heard noise and blips. After a Sysx dump, 8 times out
> of 10 it'll fix the problem...
> 
> The poly's memory is battery backup, so there is decay after years of
> no-use and makes the patches corrupt.
> 
> Erik
> 
> 
> --- In korgpolyex@yahoogroups.com, "selloutdesigns" <aah_public@>
> wrote:
> >
> > Stop me if you've heard this one before...Bought an "As Is" Poly on
> > eBay. Cleaned it up, plugged it in a lo and behold no display. Sound
> > is present at the headphone jack about 30 seconds after turning on.
> > It's a frequency sweep from low to high (sounds almost like the whoosh
> > of a jet engine starting) followed by constant white noise. This sound
> > is affected by turning VR1, VR2 and VR3 trimpots.
> > 
> > I'm okay at basic electronic troubleshooting and repair, but have run
> > out of ideas, so wondering if anyone has had a similar experience. I
> > have pretty much determined it is not a power supply circuit issue (as
> > I was hoping when I bought it). All the IC's I sampled are getting
> > correct power. Also on connector KLM596 CN6A, Pin 6 shows 4.98v, Pin 8
> > shows -5.07v and Pin 9 shows 9.44v, all of which I believe to be
> > normal and show the power section is working OK.
> > 
> > Unfortunately, I do not have access to a scope. Is it even worth going
> > any further at this point without one? In a previous post where
> > someone had a similar issue, it was mentioned that if the RES6.5 clock
> > was not running this could cause a dead display. I did check RES
> > 5.5,6.5 and 7.5 pins on M80C85A chip. RES7.5 pin shows 1.45v, but the
> > other two are 0v or at least < 1 mv.
> > 
> > Any ideas or suggestions on where to look next?
> >
>

I don't think you could measure the RES 5.5 and 6.5 with a DVM very 
well since it's such a low duty cycle pulse. You're seeing 1.45v on 
the RES 7.5 line which is probably normal. I would try to beg or 
borrow a scope to go much farther than you did. You actually did 
really well for using only a DVM. 
Other clues would be: Are any of the chips getting warm. Most 8080 
type processors when they fail get quite warm to the touch. Many 
times I have shotgunned CPU's (even though I do have a lot of test 
gear and a good scope) just because they were a lot warmer than any 
other chip on the board. I'm not sure if the CPU has to run to 
produce a sound you can vary with the filter section pots. The noise 
generator may be able to run without any outside influence. I do know 
the CPU controls the envelopes. 
The 81C55 memory chip may be a good place to start too since these 
fail quite often if a spike or any ESD hit the board.

Let us know what you find, Fran
--- In korgpolyex@yahoogroups.com, "selloutdesigns" <aah_public@...> 
wrote:
>
> Stop me if you've heard this one before...Bought an "As Is" Poly on
> eBay. Cleaned it up, plugged it in a lo and behold no display. Sound
> is present at the headphone jack about 30 seconds after turning on.
> It's a frequency sweep from low to high (sounds almost like the 
whoosh
> of a jet engine starting) followed by constant white noise. This 
sound
> is affected by turning VR1, VR2 and VR3 trimpots.
> 
> I'm okay at basic electronic troubleshooting and repair, but have 
run
> out of ideas, so wondering if anyone has had a similar experience. I
> have pretty much determined it is not a power supply circuit issue 
(as
> I was hoping when I bought it). All the IC's I sampled are getting
> correct power. Also on connector KLM596 CN6A, Pin 6 shows 4.98v, 
Pin 8
> shows -5.07v and Pin 9 shows 9.44v, all of which I believe to be
> normal and show the power section is working OK.
> 
> Unfortunately, I do not have access to a scope. Is it even worth 
going
> any further at this point without one? In a previous post where
> someone had a similar issue, it was mentioned that if the RES6.5 
clock
> was not running this could cause a dead display. I did check RES
> 5.5,6.5 and 7.5 pins on M80C85A chip. RES7.5 pin shows 1.45v, but 
the

> other two are 0v or at least < 1 mv.
> 
> Any ideas or suggestions on where to look next?
>

MIDI In/Out appears to be non-responsive. I connected the Out and ran
a MIDI monitor and saw no activity coming through (and no blinky
lights on my MIDI interface). Also no noticeable change on the Poly's
headphone out when transmitting note data through the In.

<<aaRoN>>

--- In korgpolyex@yahoogroups.com, Alec Jahn <ocedtotehmax@...> wrote:
>
> In my experience, the tape-in is really picky about volume.  You
could spend
> hours incrementing it to try and get a good blind load and then
still get
> nowhere if your Poly is actually dead.
> 
> Let us know about the MIDI.
> 
> On Mon, Feb 23, 2009 at 9:51 AM, selloutdesigns <aah_public@...>wrote:
> 
> >   I didn't try sysex (don't think the stock Poly 800 1 has any sysex
> > capability), but I did try loading up the factory patches via the
> > cassette interface. I had to do it blind though since the display is
> > dead and it did not appear to have done anything. I believe that the
> > input switches are also dead as they are on the same board as the
> > display LED's. I also tried blindly adding a manual patch, but no luck
> > there either. I may try at least hooking up the Midi side anyway to
> > see if at least the Midi In/Out is responding.
> >
> > <<aaRoN>>
> >
> >
> > --- In korgpolyex@...m <korgpolyex%40yahoogroups.com>,
"Erik
> > Hines" <sablerock@> wrote:
> > >
> > > Have you tried sending a SYSX dump of the original patches to the
> > > Poly? I have found MANY a poly\ex that were sold at garage sales and
> > > thrift stores because no-one could figure out why they didn't
hear any
> > > sound, or only heard noise and blips. After a Sysx dump, 8 times out
> > > of 10 it'll fix the problem...
> > >
> > > The poly's memory is battery backup, so there is decay after
years of
> > > no-use and makes the patches corrupt.
> > >
> > > Erik
> > >
> > >
> > > --- In korgpolyex@yahoogroups.com <korgpolyex%40yahoogroups.com>,
> > "selloutdesigns" <aah_public@>
> > > wrote:
> > > >
> > > > Stop me if you've heard this one before...Bought an "As Is"
Poly on
> > > > eBay. Cleaned it up, plugged it in a lo and behold no display.
Sound
> > > > is present at the headphone jack about 30 seconds after
turning on.
> > > > It's a frequency sweep from low to high (sounds almost like
the whoosh
> > > > of a jet engine starting) followed by constant white noise.
This sound
> > > > is affected by turning VR1, VR2 and VR3 trimpots.
> > > >
> > > > I'm okay at basic electronic troubleshooting and repair, but
have run
> > > > out of ideas, so wondering if anyone has had a similar
experience. I
> > > > have pretty much determined it is not a power supply circuit
issue (as
> > > > I was hoping when I bought it). All the IC's I sampled are getting
> > > > correct power. Also on connector KLM596 CN6A, Pin 6 shows
4.98v, Pin 8
> > > > shows -5.07v and Pin 9 shows 9.44v, all of which I believe to be
> > > > normal and show the power section is working OK.
> > > >
> > > > Unfortunately, I do not have access to a scope. Is it even
worth going
> > > > any further at this point without one? In a previous post where
> > > > someone had a similar issue, it was mentioned that if the
RES6.5 clock
> > > > was not running this could cause a dead display. I did check RES
> > > > 5.5,6.5 and 7.5 pins on M80C85A chip. RES7.5 pin shows 1.45v,
but the

> > > > other two are 0v or at least < 1 mv.
> > > >
> > > > Any ideas or suggestions on where to look next?
> > > >
> > >
> >
> >  
> >
>