waveform generator broken

Hello guys,

it seems as my Quad´s output is broken.
Unintenionally I connected the output chanel with a 12V source.

Now the amplitude of the output chanel is reduced to 0,5Volts.

The form of the waves is not correct, too. Sine, Triangle and Saw are all cut on the upper side of the signal.

It seems as the USB Port is affected by the problem, too. Loading the battery seems to work but there is no data connection even in the Firmware Mode.
(Works now on an other usb Port)

I hope you can help me with my problem and tell me which part of the hardware could be defect and i have to renew.

Best Regards from Germany,


As far as I can see on the schematic your USB should work ok as this should not have been affected. As I can see there is a Zener diode D6 cesd5v0ap this may be blown. I can not say if there is more damege or if you can replace the D6 IC as this is Smd and may be hard to solder and remove, I am shure seedstudio will help and advise. Hope this helps

Thank you for your suggestions. I hope the OpAmp is not broken. I think the 3 legs of the diode are possible to solder. But with the 5 legs of the OpAmp its a little bit harder to do. Fortunateley all the components are mounted near the edge of the board so they are easy to reach.

If you have any other Ideas or you know what to meassure on the different points of the output circuit please let me know.

I would suggest using the Quad (if you have no other scope) to measure the signal at U7-pin-3 and pin-1. My guess about statistical failures would be D6 first and U7 second. If the U7-pin-3 signal is defective, I would then unsolder U7 (or leave the leads soldered, but cut the chip body out with side cutters). If the U-7-pin-1 signal is present but distorted, then unsolder D6 (or leave the leads soldered, but cut the chip body out with side cutters) and repeat tests.

The reason I say to break out the chip body is so you could have someone else with more soldering experience replace the defective components. Take care not to damage any traces under the chip or adjacent to the chip while cutting out the chip body.

This would be my approach to fault isolation of this failure.

I simulated a broken Z-diode with an SPICE simulation and the results matched with the values I measured. After I opened the Quad I could see that the metal that seperates the PCB from the battery had a discoulouration exactly over the D6 diode. If sombody knows where to buy a new CESD5V0AP in Germany or Europe please tell me. All Zener Diods I found here in a SOT-23 package have only one Diode Inside (That is ok in my oppion) with a Z voltage of 5.1V (That is OK in my oppinion, too) but it is always connected in the wrong direction so i can not replace D6 it with one of these.

hi,i think you should:

  1. unsolder the D6 first , and then test if the signal out ok
  2. if ok , then you can replace the D6 with any Diode( Z voltage of 5.1V)in your hand .like the means below:111.jpg
    3 . as the USB, it should be another issure. please state it more clearly

Replacing the Zener diode seems not as easy as you tell it here :frowning: . Soldering, measurement and replacing the diode seems to be possible. It is a problem to find a Zener that is connected in the correct direction. It seems that all Zeners in a SOT23 package you can buy here in Germany are connected in the opposite direction as the CESD5V0AP is. So I can not replace it so easely.

(Example for Zener in Germanyhttp://www.reichelt.de/SMD-Z-Dio … 369bfad8b2)

Try soldering a 5v1 Zener to pads as above. Don’t bother with looking for SOT-23 package. The two pads one side will be linked by track so you should only need to solder to one as above. When removing SMD I cut the legs with a scalpel and removed rest after. Hope this helps

you do not need to find a SOT23 package . a two-pads Zener works also.

Thank you guys,

I fixed the problem.

No problem, back to playing with it now.