SV: Re: SV: RE: [sdiy] Arp Axxe rescue help

[Karl Ekdahl]

Well, i don't see a zener, but i assume you mean Q1
which is supposed to be the transistor that generates
the noise. The thing is *there is* noise at the +
input of Z2. It's pretty quite but should that really
matter? I'm thinking that as long as there's
*something* at Z2's + input the output should give a
strong noise output - yes? 

Btw. service manual (if needed) can be found here:
http://www.synthdiy.com/show/getfile.asp?get=916

thanks

Karl

--- Chris Manders <wight446 at yahoo.com> skrev:

> Capacitors are notorious for 'dying' in Noise
> Generator circuits. Try replacing the first
> capacitor,
> directly after the noise zener.
> 
> Chris
> 
> 
> --- Karl Ekdahl <elektrodwarf at yahoo.se> wrote:
> 
> > Hi,
> > 
> > The sustain slider was dead but i seem to have
> fixed
> > that, i also replaced one of the op.amps. in the
> > ADSR
> > and now that part seems to be working fine.
> > 
> > With the noise i've replaced both op.amps. without
> > any
> > luck, i do however have a noise signal at the +
> > terminal of the Z2 op.amp. but there's nothing
> > coming
> > out of it. I also tried to replace the C5
> tantalum.
> > Z2's configuration confuses me (it's also 4:22 in
> > the
> > morning), should i have a amplified or
> > "de-amplified"
> > signal on the output?
> > 
> > So regarding those sliders, four of them are
> missing
> > (i temporarily installed pots) and the existing
> ones
> > are really really crappy. I managed to clean one
> of
> > the sliders using rubbing alcohol, but a) i've
> heard
> > this is not reccomended and b) they still need
> some
> > kind of grease or something. What do i need to
> > clean/grease them? Should i just try and buy new
> > ones?
> > If so, is there a source for these or similar
> > sliders
> > that aren't outrageously expensive (saw 2 sliders
> > for
> > $20 on ebay - fat chance).
> > 
> > Question about tantal caps: Those tantal caps that
> > have failed me i have replaced with electrolytics.
> > As
> > i understand this is recommended due to their
> > failure
> > rate - right? I'm thinking that maybe i should
> > replace
> > them all - especially since it seems that the
> whole
> > reason that so many components in this synth is
> > blown
> > away is because of a single tantal failure.
> > 
> > thank you!
> > 
> > Karl
> > 
> > --- Eric van Baaren <eric at piramiden.demon.nl>
> skrev:
> > 
> > > Hi Karl,
> > > 
> > > the adsr: check the sliders. and while you're at
> > it
> > > check all the
> > > sliders..big chance there are a few dead
> sliders.
> > > noise: most of the time one of those opamps is
> > gone.
> > > just replace both,
> > > vca leaking: gain slider doesn't go back 0 ohm.
> > > 
> > > best,
> > > 
> > > Eric van Baaren.
> > > _________________
> > > http://www.sainteric.nl
> > > 
> > > 
> > > 
> > > 
> > > -----Oorspronkelijk bericht-----
> > > Van: owner-synth-diy at dropmix.xs4all.nl
> > > [mailto:owner-synth-diy at dropmix.xs4all.nl]Namens
> > > Karl Ekdahl
> > > Verzonden: vrijdag 2 juni 2006 3:49
> > > Aan: synth-diy at dropmix.xs4all.nl
> > > Onderwerp: [sdiy] Arp Axxe rescue help
> > > 
> > > 
> > > I found a Arp Axxe laying on the sidewalk
> > yesterday,
> > > pretty badly beaten up. After some smoke and
> > fixing
> > > these problems persist:
> > > 
> > > The ADSR doesn't seem to work, the only pot that
> > > does
> > > what it should is the attack pot. The
> > decay/sustain
> > > are dead and the release works more like a
> > > "release-sustain value". I've noticed that if
> the
> > > Attack is in it's bottom position (fastest)
> > there'll
> > > allways be some sound coming out of the
> > synthesizer
> > > (regardless of VCA trim). I have some problems
> > > following the ADSR schematic, but it seems to me
> > > that
> > > since both decay/sustain are dead, possibly it's
> > > just
> > > the sustain that is really malfunctioning? I'd
> > > really
> > > like to get some pointer on the works of this
> > > circuit.
> > > 
> > > The second thing is the VCA; i thought that the
> > > above
> > > ADSR problem had to do with the VCA trim but it
> > > apparently doesn't. However i noticed one
> > curiosity;
> > > if probing the output of the VCA trimmer with my
> > > multimeter the synth starts picking up radio!
> This
> > > screams major-error to me... yes?
> > > 
> > > The Noise source (hence the S/H) is completely
> > dead,
> > > the output of Z2 is nil while Z3 is - yet again
> -
> > > picking up radio (allthough this time *through*
> > the
> > > oscilloscope probes, i have a crappy soundcard
> > scope
> > > so i notice :) ).
> > > 
> > > If anyone has experience with the Axxe and wants
> > to
> > > help me out it'd be greatly appreciated!
> > > 
> > > thanks
> > > 
> > > Karl
> > > 
> > > 
> > 
> > 
> 
> 
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