[sdiy] Korg Polysix major problems - Update

Fri Oct 24 16:56:08 CEST 2008

Karl,

I get at least 2 Polysixes in for repair a month, and besides the common battery problem I just had 1 with a dead 8049 CPU so far...
Very often the SRAM is dead, what leads to weird behaviour or a non-functioning unit. Did you check this? I did not follow this thread, but I thought I ask anyway ;)
Threadnap: I also might be interested in 1 or 2 spare 8049-217 CPUs for repair purposes... hint, hint ;)

Best wishes,

Tobias

> -----Ursprüngliche Nachricht-----
> Von: "Karl Ekdahl" <elektrodwarf at yahoo.se>
> Gesendet: 24.10.08 16:40:32
> An: "synth-diy at dropmix.xs4all.nl" <synth-diy at dropmix.xs4all.nl>
> Betreff: Re: [sdiy] Korg Polysix major problems - Update

> Guys
> 
> One last question before i give up on this CPU; how common is the problem of the CPU dying and *which* CPU are we talking about, the 8048 or the 8049 (i believe the latter might be my problem). The reason i'm asking is because i in fact have two sets of boards for the polysix and each board behaves the same which i thought was kinda weird. I have of course tried swapping the CPUs inbetween the boards as well as hooking up all of the boards with eachother in different configurations.
> 
> Karl
> 
> 
> --- Den fre 2008-10-24 skrev Ullrich Peter <Peter.Ullrich at kapsch.net>:
> 
> > Från: Ullrich Peter <Peter.Ullrich at kapsch.net>
> > Ämne: Re: [sdiy] Korg Polysix major problems - Update
> > Till: "elektrodwarf at yahoo.se" <elektrodwarf at yahoo.se>, "Bob Weigel" <sounddoctorin at imt.net>, "synth-diy at dropmix.xs4all.nl" <synth-diy at dropmix.xs4all.nl>
> > Datum: fredag 24 oktober 2008 08.26
> > Hallo Karl!
> > 
> > It seems that you could use a new programmed 8748 or 8749
> > microcontroller.
> > As you are from Sweden as your emailaddress tells me you
> > may be interested
> > in getting a new microcontroller from me.
> > 
> > I need to have a look but I am quite sure that I still have
> > some left.
> > It would cost 10 Euro + postage.
> > 
> > Mail me privately if your interested and I will have a look
> > if I can find
> > A chip.
> > 
> > Tip: If your existing microcontroller is socketed (normally
> > they are) try
> > To remove it and put it in again - maybe the malfunction it
> > is just because
> > of corrosion.
> > 
> > Ciao
> > Peter
> > 
> > http://www.ullrich.at.tt
> > 
> > 
> > -----Ursprüngliche Nachricht-----
> > Von: synth-diy-bounces at dropmix.xs4all.nl
> > [mailto:synth-diy-bounces at dropmix.xs4all.nl] Im Auftrag von
> > Karl Ekdahl
> > Gesendet: Freitag, 24. Oktober 2008 04:27
> > An: Bob Weigel; synth-diy at dropmix.xs4all.nl
> > Betreff: Re: [sdiy] Korg Polysix major problems - Update
> > 
> > 
> > Bob
> > 
> > > Well normally there will be a dead or multiple dead
> > lines that should
> > > be chugging away with the clock generating data and
> > addresses.
> > 
> > Oh no, i just verified that out of the eight lines going
> > out of the processor (pin 34-27) only two are actually
> > having any data on them, the others are totally stale.
> > 
> > > And then you
> > > have to establish if it's the cpu or something
> > pulling a line down.
> > 
> > Hmm.. i didn't even realize these lines both go to the
> > keyboard as well as to the KLM-371 - perhaps if i disconnect
> > the cable to that board i'll at least see on which board
> > the problem is.
> > 
> > > The code is inside of course so unless it's
> > rapidly halting for some
> > > reason there should be stuff going on with all those
> > lines.
> > >  I can't
> > > recall off the top how reset etc. are set up on that
> > chip so consult
> > > diagram and besure those lines are doing what they
> > should do also.
> > > Usually held low a reset is active to keep the chip
> > out of the game.
> > > -Bob
> > 
> > Now i'm a little confused; are we talking hardware
> > (memory) reset or a soft reset while power is on? I know
> > there's a reset POT on the KLM-371 board but i don't
> > really know what it's doing, guess i've gotta dig
> > into the 8048/8049 datasheets...
> > 
> > As it does seem like i might need a new processor, did you
> > say you had some? Would you be ok parting with one in that
> > case and for how much?
> > 
> > Thanks
> > 
> > Karl
> > 
> > > Karl Ekdahl wrote:
> > >
> > > >So, it turns out that there is a good clock going
> > to
> > > IC4 / IC5 that handles the gates, it's just not
> > doing anything - the
> > > data coming in seems fine and the reset is constantly
> > held HIGH as far
> > > as i can tell. I desoldered IC4 and tried triggering
> > the gate on voice
> > > 4 manually and indeed it works just fine! The thing is
> > though that it
> > > doesn't change frequency when i push any of the
> > keys and the D/A i've
> > > verified to work so perhaps there's something else
> > busted in the
> > > keyboard section?
> > > >
> > > >
> > > >
> > > >>I've had a cpu go bad on that board.
> > > That'd be
> > > >>first guess. You can of
> > > >>
> > > >>
> > > >
> > > >How do i verify if the CPU is dead?
> > > >
> > > >Thanks
> > > >
> > > >Karl
> > > >
> > > >
> > > >
> > >
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