troubleshooting waveshield

[sgtserg]

I recently soldered the shield together and went to use it and no-go. Besides building things I also want to learn how to troubleshoot when it doesn't work. Having access to an oscilloscope I was checking different components and I am assuming that the issue may be near the op amp.

Here's what I did:
1. downloaded example wave files and when I compile and check serial monitor it seems to be playing ok. So it should be reading sd card ok.

2. check the DAC and it's putting out the voltage.

3. Here's where I need help. I connected the probe to the input of the amp and as I adjust the potentiometer the levels adjust from 2 - 7 mV. On the output side I am not getting anything. This is why I assume the issue may be here.

Would like to know where else to check because I would like to learn how to fix this because this is a good learning experience.

[adafruit_support_bill]

So, you have a signal on pins 3 & 5, but not on pins 1 & 7 of the op-amp?

Check that you have the chip installed in the correct orientation. And check the soldering on all the op-amp pins. If you post photos of the front & back of the board, we'll take a look too.

[sgtserg]

Here are the wave shield pics.

[adafruit_support_bill]

Soldering looks mostly good. A few joints look a little balled up around the pin. Sometimes that means they haven't properly wetted the solder pad. Touch those up with a hot iron.

On the output side I am not getting anything.

Where are you measuring that? On pin7 of the op-amp? Or at the speaker terminals? Check the speaker to make sure you don't have a shorted coil.

[sgtserg]

Under closer observation i noticed one of the welds is pretty bad. I'm going to have to use my magnifying lamp to go over the welds again.

Just out of curiosity, what should my input voltage should be going into the op amp and what should be my output voltage?
I was checking on the output pin 7 and getting about 30mV. What should be my output voltage on pin 8 of the DAC? I want to get an idea to try to narrow it down where the issue might be.

I tried a piezzo buzzer in case it was the speaker but no luck there. Would soldering a capacitor backwards be causing my problem?

[adafruit_support_bill]

The output level of the DAC depends on the amplitude of the encoded waveform. But it can be up to 5Vpp. If you are only getting a few mV out, then we probably need to look further upstream for the problem. Once you touch up any suspicious looking solder joints, check the DAC output again.

[sgtserg]

Thanks for the suggestion. Will have to look harder. I was wondering if I can use a function generator and insert a signal at different points to see if that may help me locate the problem. Is it wise to do this or may it create more problems?

[adafruit_support_bill]

You can use it to verify the analog output part of the circuit. If it is not more than 5v pp at the output of the DAC it should not be a problem.

[sgtserg]

I finally got around to working on the shield and after inserting a 5khz at the DAC output and heard a sound, I decided to to re-solder some of the joints that didn't look perfect. As soon as I plugged in the USB cable, I was startled because I had previously uploaded the the Halloween wave files and I heard a scream. That was a good sign. So now I can say it officially works and I got some troubleshooting experience. Have a good day.

[adafruit_support_bill]

Congratulations! Good work