+/-5V rails on the joystick seem ok.. in the power stage, the caps
look fine on the outside.. which ones of the transistors would be
likely to get whacked? the diodes there would protect them from
reverse current, right?
on IC IC25 most pins from 20-40 show no voltage.. Neither do the leds
or the transistor array driving them.. didn't test all of the ICs but
apart from these they were all showing voltage on the pins
Any ideas?
Thanks!
Jouni
--- In korgpolyex@yahoogroups.com, Marcus Wilson <JB@...> wrote:
>
> check at the joystock for the +/- 9V and the +/-5V
> id be thinking its your power input stage to the whole poly
>
> especially if you are not getting the LED display up
>
> best regards,
>
> JB
>
> On 25/02/2007, at 1:38 AM, dharmaone1977 wrote:
>
> > I've checked it with the multimeter now and the pin 9 and 8 on the
> > 80C85 show 5v DC.. it doesn't respond to setting any parameters or
> > the keys, just stays at this noisy sound after the initial
> > filter/frequency sweep
> >
> > any ideas?
> >
> > 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!!"
> > > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > ---------------------------------
> > > Finding fabulous fares is fun.
> > > Let Yahoo! FareChase search your favorite travel sites to find
> > flight and hotel bargains.
> > >
> >
> >
> >
>