Doepfer

Hi at,

A few simple things may be worth checking:

1. The resonance path is internally wired through the 'switching 
contact' on the lower 'res insert' socket, as shown by the arrow on 
the faceplate: it's possible this may not be making contact - 
manually insert a patch cord between the two sockets and see if that 
makes any difference. (Inserting a patch lead into the lower 'res 
insert' socket, with the other end unconnected, *does* completely 
kill the resonance.)

2. There are quite a few jumpers on the PCB, most of which don't have 
the little jumper in place - however make sure there is nothing 
at 'JP8', as this will impact on the resonance path too. (Jumpers JP7 
and JP4 are described in the manual pages for the module - it might 
be worth checking they are as required too.)

As for trimmers, the two that are there just affect the cut-off 
frequency and scaling, so I doubt would have any effect on the 
resonance as you describe.

If neither of the two ideas above work, then you may be looking at a 
damaged module. The 'DS20' chip is not an OTA: I'm not really sure of 
Doepfer's reasons for concealing its identity, as what it is is 
fairly obvious if you know roughly what you are looking for (I 
guessed its identity after about 5 minutes looking at the circuit, 
but it took perhaps 30 minutes to verify the guess with some tests!). 
I think it is unlikely that it has blown, but the chip *is* being 
used in a way that I doubt the manufacturers would recommend, which 
results in current flowing through it in a way which wouldn't happen 
under 'normal' use. However I also doubt that this could result in 
its premature failure, as I suspect we would have heard of it by now 
from other list members.

Hope this helps.

Tim


--- In Doepfer_a100@yahoogroups.com, "atuzzi" <antoniotuzzi@...> 
wrote:
>
> Hello friends.
> 
> I have this a106, that I used very little in the last 8 months.
> 
> I decided now to use it (well done!)
> 
> But:
> I can't hear the resonance. I know very well the ms20. but my module
> is doing a very impercettible variation to the sound moving the RES 
knob.
> 
> Is there any trick I need to use to jumpstart the RESO ?
> any trimmer to trim ?
> Is anybody experimenting my same problem?
> what's the white marked IC "DS20"? (is an LM13600?)
> 
> I feel I have to change that one, the only one that can be an OTA on
> the board.
> 
> Thank you for your help
> at
>