[sdiy] Arp Avatar ADSR problem

[Tony K]

Hi Karl, I don't know if you got this fixed yet by substitution.

After studying the ADSR cct description in the 
service manual you might want to check the 
peak-detector, Q15, this is supposed to supply a 
'feedback' 10 V (max) and reset the Attack latch, 
Q17 and Q18. I have a 2800 on the bench now if you want me to scope around.

Tony K



At 08:06 PM 6/2/2009, Karl Ekdahl 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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