Doepfer

i just purchased the DIY kit #2 from analog haven and i am having some weird issues with 
it.

only a few modules work correctly, a few not at all and a few with a very bad ground hum.

the doepfer mixer and spring reverb work fine. the cwejman and dual LFO do not work at 
all, they just hum. The cwejman dual filter works fine
 and the doepfer 188 noise sorta works, it takes about 45 seconds to start working and 
has a very bad ground hum????

I have tested them after having used the DIY kit in a doepfer portable case and they all 
work fine.

to the best of my knowledge i have bus board connected correctly -- i tried it at analog 
haven and tested it with a doepfer high quality osc and it worked fine. then did not touch 
it after that.

here is a link to a picture of the wiring to be sure i got it correct:

http://www.monsturo.org/DIY_kit.jpg

The power supplies are matching and output 12VDC 500mA, and all the leds on the bus 
board light up correctly...

really not sure what is going on, has anyone else had this issue? Any help would be very 
much appreciated.

Best,
--david

sorry there is a typo in the original message -- i forgot to identify the cwejman oscillator as 
one of the modules that does not work, it only hums same with the cwejman dual LFo.

Hi david

> only a few modules work correctly, a few not at all and a few with a very bad ground hum.
Did you measure both voltages with one of the "bad" modules plugged in?

Did you check the modules separately one after the other, or did you 
plug in all at the same time? If the latterm then try them separately.

I do not know the non-Doepfer modules you mentioned, but maybe they rely 
on a connection frontplate -> electrical-ground (0Volts).

Florian

unfortunately i have no way of measuring the voltages, but they were all plugged in separately.

there are 3 modules that work (cwejman filter, doepfer spring reverb & 138 dopfer mixer)

and three that do not (cwejman LFO & Oscillator and the doepfer 118 noise).

The 2 cwejman modules that are not working are both 80mA or more so i thought that 
might be the problem? though the 118 is only 20.

I tried connecting the ground from the bus board to the rails and that did nothing.

I does seem like a ground issue though since the noise module hums as do the non 
working cwejman modules. Funny thing is that the spring reverb does not hum... 

Thanks for the help!! would love to get this sorted out ASAP.

thanks,
--david


--- In Doepfer_a100@yahoogroups.com, Florian Anwander <Florian.Anwander@...> 
wrote:
>
> Hi david
> 
> > only a few modules work correctly, a few not at all and a few with a very bad ground 
hum.

> Did you measure both voltages with one of the "bad" modules plugged in?
> 
> Did you check the modules separately one after the other, or did you 
> plug in all at the same time? If the latterm then try them separately.
> 
> I do not know the non-Doepfer modules you mentioned, but maybe they rely 
> on a connection frontplate -> electrical-ground (0Volts).
> 
> Florian
>

well i just went out and bought a meter and tested the voltages -- 15.5 for both positive 
and negative. i assume this is the problem?

could this be the power supplies? they both say 15VDC 500mA.

thanks,
--david

--- In Doepfer_a100@yahoogroups.com, Florian Anwander <Florian.Anwander@...> 
wrote:
>
> Hi david
> 
> > only a few modules work correctly, a few not at all and a few with a very bad ground 
hum.

> Did you measure both voltages with one of the "bad" modules plugged in?
> 
> Did you check the modules separately one after the other, or did you 
> plug in all at the same time? If the latterm then try them separately.
> 
> I do not know the non-Doepfer modules you mentioned, but maybe they rely 
> on a connection frontplate -> electrical-ground (0Volts).
> 
> Florian
>

oops! i meant to say both power supplies are 12VDC 50mA

--- In Doepfer_a100@yahoogroups.com, "david rothbaum" <david@...> wrote:
>
> well i just went out and bought a meter and tested the voltages -- 15.5 for both 
positive 
> and negative. i assume this is the problem?
> 
> could this be the power supplies? they both say 15VDC 500mA.
> 
> thanks,
> --david
> 
> --- In Doepfer_a100@yahoogroups.com, Florian Anwander <Florian.Anwander@> 
> wrote:
> >
> > Hi david
> > 
> > > only a few modules work correctly, a few not at all and a few with a very bad 
ground 

> hum.
> > Did you measure both voltages with one of the "bad" modules plugged in?
> > 
> > Did you check the modules separately one after the other, or did you 
> > plug in all at the same time? If the latterm then try them separately.
> > 
> > I do not know the non-Doepfer modules you mentioned, but maybe they rely 
> > on a connection frontplate -> electrical-ground (0Volts).
> > 
> > Florian
> >
>

hi David,

> I does seem like a ground issue though since the noise module hums 
as do the non 
> working cwejman modules. Funny thing is that the spring reverb does 
not hum... 

I think it may be the ground too. From the photo of the kit at 
Doepfer's site, to produce -12V - 0 - +12V from two identical 
wallwarts, the '0V' from neither of them can actually be ground 
(hence why it is OK to run them in series, with the '+12V' of one 
connected to the '0V' of the other, essentially giving the required 
24V), and I'm assuming that you have been given something very 
similar by Analog Haven. Thus when you have modules hooked up and 
connected to other equipment, there may not be a decent ground 
reference for the modules connected to the kit, which might then act 
weirdly (though I'm a little surprised that any patch leads are not 
supplying this). I'd suggest connecting the ground on the kit bus 
board to a suitable ground somewhere on the external equipment, and 
see what that does.

Tim

yes i tried this -- grounding it to something else and that did not solve the problem. my 
feeling is that there is an issue with the power supplies.

--- In Doepfer_a100@yahoogroups.com, "Tim Stinchcombe" <timothy@...> wrote:

>
> hi David,
> 
> > I does seem like a ground issue though since the noise module hums 
> as do the non 
> > working cwejman modules. Funny thing is that the spring reverb does 
> not hum... 
> 
> I think it may be the ground too. From the photo of the kit at 
> Doepfer's site, to produce -12V - 0 - +12V from two identical 
> wallwarts, the '0V' from neither of them can actually be ground 
> (hence why it is OK to run them in series, with the '+12V' of one 
> connected to the '0V' of the other, essentially giving the required 
> 24V), and I'm assuming that you have been given something very 
> similar by Analog Haven. Thus when you have modules hooked up and 
> connected to other equipment, there may not be a decent ground 
> reference for the modules connected to the kit, which might then act 
> weirdly (though I'm a little surprised that any patch leads are not 
> supplying this). I'd suggest connecting the ground on the kit bus 
> board to a suitable ground somewhere on the external equipment, and 
> see what that does.
> 
> Tim
>