Well, wonders never cease! I was completely sure, that after reading
your post in the wee hours this AM that you were long gone from the
group and that I would have little to nil chance of you reading my
post and responding. What's more that you did the next day! This is
all getting a little strange. My new Poly-800 really wants to LIVE!
What crucial info, too! I read your post and my heart sped up a bit
because I knew that I had the same problem, replicated. And since you
had said that you fixed yours I knew there was a chance. BTW, my
head-phone amp is fine, very clear indeed and plenty loud!
I agree, I think that I have a 5V+/- situation here and I'll look at
those three tranies straight off. I might as well check up from each
leg a bit to see if anything went with it. Fingers are crossed, I may
have to visit the magic 8-ball! We never know till either the thing
works or the essential blue smoke comes out of it. What-ever the
outcome, you have my most sincere thanks! I hope to post a "happy
ending" post early in the week. As for now I am going to be taking
advantage of our fine city's free dump week-end. I am going to rid
myself of a few year's worth of things. I'll do the Korg benchwork on
Monday most likely. See you then, and keep those cards and letters
coming about this issue. We aren't through diagnosing this puppy yet.
News at 11.
Rob
--- In korgpolyex@yahoogroups.com, Marcus Wilson <JB@...> wrote:
>
> G'day Rob
>
> Ive now resurrected 2 korgs from dead state, with no display on the
> LED's
>
> it seems from both of mine that the issue was with the +5/-5V
> generation circuit
>
> The second one also had a dead op-amp in the headphone out circuit
> which i managed to get sorted again and both are now happy
>
> To check whether this is the problem with yours, take some readings
> at the joystick for the +5 -5V where the connector plugs in
>
> if these are not showing the appropriate voltages, its a fairly good
> chance that the 3 input transistors have gone bunky, and not
> generating the voltages for the LED circuitry etc
>
> check out Q1 Q3 and Q18 to make sure they are functioning correctly
>
> the schematics for the poly are stored in the archive for this newsgroup
>
> good luck!
>
> Marcus Wilson
>
> On 21/04/2006, at 1:03 PM, Rob 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!!"
> >
> >
> >
> >
> >
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
> >
> >
>