SV: RE: [sdiy] Arp Axxe rescue help

[Karl Ekdahl]

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
> 
>