Doepfer

Hi Tim,

both chips, 555 and TL084 are working properly. also the
potentiometers seem to be ok. atm i am measuring V inbetween 2 boards
having the same settings. lets see what  i find.

thanks


--- In Doepfer_a100@yahoogroups.com, "Tim Stinchcombe" <timothy@...>
wrote:
>
> Hi Helitron, Florian,
> 
> > properly on there, and since it was working before it has to be some
> > component that is dead. guess i have to exchange the potentiometers.
> 
> I'd be very surprised if changing any pots cures the problem, and 
> besides, you could probably check that sustain pot is OK more easily 
> by getting the envelope in a 'working' state (you seemed to suggest 
> that was possible some of the time), and check the voltage at the pot 
> wiper when in 'decay', so see if it varies much - should be something 
> like close to 0V to around 8V maybe (looks like a 10k pot from 
> Florian's photo).
> 
> I don't have that module, so I don't know the full details of the 
> circuit and how it works, but from the photos Florian posted I'm 
> guessing IC2 must constitute 'logic' which is controlling the 555, 
> and that is where I suspect the fault will be. If the chips are 
> socketted (?), a reasonable tactic would be to take the chips one at 
> a time from the bad section (EG3), and try them in one of the good 
> sections - if the good section continues to work, the chip is good, 
> if not then you have id'd a bad chip. (If you put the chips from a 
> good section into the bad the one, there is a small chance that the 
> fault in the bad section might trash the good chip...)
> 
> I can't quite make out the IC2 designation on the layout photo, but 
> it looks like it could be simply a quad op amp chip (TL084/064?), 
> perhaps used as comparators, but that doesn't quite tie-in with 
> the 'JPx' (?) boxes on the schemo, which control the re-triggering 
> and the 'reset' pin of the 555. And reading the manual, on page 2, 
> that the 'end of decay' switches at the sustain level setting, I 
> suggest that what ever causes this is what is mucking things up!?
> 
> Tim
>