Archive of the former Yahoo!Groups mailing list: Korg Poly800/EX800 Users

and the +/- 9V rails?

On 26/02/2007, at 11:37 PM, dharmaone1977 wrote:

> +/-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!!"
> > > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
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