SammichFM audio output distortion, ideas??

[Cutter]

Hey all! Just finished putting together my wonderful kit from Wilba. Unfortunately the audio output is very low in volume and distorted. I made sure my audio jacks are properly soldered. Other then that, I'm not sure how to approach troubleshooting. I've recorded a couple examples of the audio output to hopefully help the midibox sleuths. The first audio sample is what is sounds like with midi input, the second is what it sounds like without any midi input. Ideas??? Thanks in advance!!!

sammichFM_trouble1.mp3

sammichFM_trouble2.mp3

Edited November 16, 2011 by Cutter

[nILS]

Got pictures of the area with the YACs and the opamps?

[Cutter]

I checked all the joints through a loupe, and they seemed to look okay. Here's pics of the yacs and opamps. Follow the link :thumbsup:

http://www.flickr.com/photos/carsonlabs/#photo6355824585

Thanks so much for the help nILS!

[Cutter]

Ah, I forgot to mention that I hit a couple so-so looking joints with a bit more solder. Now it doesn't make any sound when plugged in and triggered. :sad:

[Cutter]

After looking at the pictures I noticed how much flux/resin there was around the joints. I cleaned it up, and did another audio test. It makes the with midi noise very very quietly now. Without midi the same sound as what I uploaded.

[monokinetic]

Hi Cutter,

Maybe you have tried this info from the SammichFM guide already, but just in case you missed it:

Have you got a multimeter? If yes, have you tried measuring for continuity between each SMD chip pin and the next part of the track on the PCB that is connected to it? i.e. to make sure that the solder joint is connecting the SMD chip's pin to the rest of the circuit.

Have you checked for continuity between all the adjacent pins on each of the SMD chips? i.e. to make sure there are no shorts between the pins next to each other.

For more info see Step 1.12 and 1.13 from the SammichFM building guide! :)

David

[Cutter]

Alright! We've got sound! I accidentally swapped the B337 transistor and the 78L05 regulator. I replaced both with new components. Now the screen is blocking out half the time I turn it on, and then when it works, it tends to freeze the screen without affecting the sound output. Any ideas? I doubled checked all the joints on the headers, and they look good. I also did continuity and voltage checks on the main board, which all turned out ok. Thanks for the help!

[Cutter]

Alright! We've got sound! I accidentally swapped the B337 transistor and the 78L05 regulator. I replaced both with new components. Now the screen is blocking out half the time I turn it on, and then when it works, it tends to freeze the screen without affecting the sound output. Any ideas? I doubled checked all the joints on the headers, and they look good. I also did continuity and voltage checks on the main board, which all turned out ok. Thanks for the help!

Turns out I just had some cold joints on the LCD header.