Doepfer

I just purchased a damaged second hand a-136 Waveshaper. Looking at the PCB I think the module has had it's power conection hooked up the wrong way around at some point in it's life. The chip (75H21EK LM324n) that is hooked up to the amp knob via a yellow wire has a black burn mark under it and on the reverse side the solder is slightly blackened, as is the PCB.

I guess the chip could be blown? The rest of the module looks fine.

How it sounds? All of the knobs still have an effect although the module only seems to produce sound in the negative range and the ext.level CV inputs don't seem to do anything. It only cost £20 and still produces some nasty sounds!

Any help would be great :)

> I just purchased a damaged second hand a-136 Waveshaper. Looking
> at the PCB I think the module has had it's power conection hooked
> up the wrong way around at some point in it's life. The chip
> (75H21EK LM324n) that is hooked up to the amp knob via a yellow
> wire has a black burn mark under it and on the reverse side the
> solder is slightly blackened, as is the PCB.
>
> I guess the chip could be blown? The rest of the module looks fine.
>
> How it sounds? All of the knobs still have an effect although the
> module only seems to produce sound in the negative range and the
> ext.level CV inputs don't seem to do anything. It only cost £20
> and still produces some nasty sounds!
>
> Any help would be great :)

I'd recommend to replace the two quad operational amplifiers LM324. They are
low cost parts and should be available for much less than 1 US$.

Best wishes
Dieter Doepfer

Thanks Dieter, So both LM324 amplifiers are identical? Is it worth replacing the socket the chip plugs into?

I guess I order one of the top two chips below:

http://www.rapidonline.com/Electronic-Components/Integrated-Circuits/Operational-Amplifiers/Operational-amplifiers/67379/kw/82-0228?source=googleps&utm_source=googleps

Thanks,
Jonathan



--- In Doepfer_a100@yahoogroups.com, <yahoo@...> wrote:

>
> > I just purchased a damaged second hand a-136 Waveshaper. Looking
> > at the PCB I think the module has had it's power conection hooked
> > up the wrong way around at some point in it's life. The chip
> > (75H21EK LM324n) that is hooked up to the amp knob via a yellow
> > wire has a black burn mark under it and on the reverse side the
> > solder is slightly blackened, as is the PCB.
> >
> > I guess the chip could be blown? The rest of the module looks fine.
> >
> > How it sounds? All of the knobs still have an effect although the
> > module only seems to produce sound in the negative range and the
> > ext.level CV inputs don't seem to do anything. It only cost £20
> > and still produces some nasty sounds!
> >
> > Any help would be great :)
> 
> I'd recommend to replace the two quad operational amplifiers LM324. They are
> low cost parts and should be available for much less than 1 US$.
> 
> Best wishes
> Dieter Doepfer
>

> Thanks Dieter, So both LM324 amplifiers are identical?

Yes

>Is it worth replacing the socket the chip plugs into?
No

> I guess I order one of the top two chips below:
> 
> http://www.rapidonline.com/Electronic-Components/Integrated-Circui
> ts/Operational-Amplifiers/Operational-amplifiers/67379/kw/82-0228?
> source=googleps&utm_source=googleps

Yes, but pay attention not to order the smd types.

Best wishes
Dieter Doepfer

I replaced both amps and the A-136 is working great. Thanks Dieter!

http://soundcloud.com/user8805415 (Waveshaper test)

Jonathan



--- In Doepfer_a100@yahoogroups.com, <yahoo@...> wrote:

>
> > Thanks Dieter, So both LM324 amplifiers are identical?
> 
> Yes
> 
> >Is it worth replacing the socket the chip plugs into?
> No
> 
> > I guess I order one of the top two chips below:
> > 
> > http://www.rapidonline.com/Electronic-Components/Integrated-Circui
> > ts/Operational-Amplifiers/Operational-amplifiers/67379/kw/82-0228?
> > source=googleps&utm_source=googleps
> 
> Yes, but pay attention not to order the smd types.
> 
> Best wishes
> Dieter Doepfer
>