[sdiy] Arp Avatar ADSR problem

[Karl Ekdahl]

Hi

> How do the pots test out. I had an
> Avatar in which 3/4 of the pot throw was out of whack
> (either a short or open circuit, forgot which). They felt
> fine but the resistive material was deteriorated/
> corroded...or something. Don't know if this will be the
> cure for your problem but when I read your description I
> though 'faders'.

Well the attack-phase of the ADSR actually works just fine and the fader does change the time, it's just that the faster attack settings somehow creates this damned oscillation that prevents the decay-circuitry to work. It looks like that particular part of the circuitr it's actually starting to self-oscillate, hence why i changed all caps - but to no avail.

Karl

> 
> 
> p.
>  
> 
> On Tue, Jun 2, 2009 at 7:06 PM,
> Karl Ekdahl <elektrodwarf at yahoo.se>
> wrote:
> 
> 
> 
> Hi list, got this Arp Avatar with problems on the ADSR,
> basically the decay doesn't work if the ADSR is set
> below a certain point, it will just keep sustaining at max
> volume until the gate is released. I checked the schematics
> (www.synthdiy.com/show/?id=2156
> page 34) and what happens is that there's an oscillation
> on the decay-trigger (junction of CR14 & CR15) when the
> attack is set too low. Now Q16 and Q18 are already replaced,
> i also replaced C8 just in case - bot to no avail.. Any
> clues before i go ahead and replace everything?
> 
> 
> 
> 
> Thanks
> 
> 
> 
> Karl
> 
> 
> 
> 
> 
>     
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