I figure out what was happening and the unit does work BUT the output sound level is far to low so I had to crank everything up to hear any effect. That is all pots are to the max, the trimmer resistance is set to max (saturating the DAC) and the volumen of my amplifier is set to max, and it is Fender frontman 25R which is pretty loud under normal circumstances. Having done that the tremolo effect is pretty nice
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I tried to troubleshoot my unit and replaced all three chips with other spare parts but that did not work. I assume that might have to do with some faulty part at the output stage that is affecting the bias point of the operational amps but I am not sure. I got all my parts from mouse electronics using the Bill of Material for the SHIELD all but the 1uF caps that were sold-out. I got mine from amazon: (Panasonic ECE-A1HKA010 Capacitor, Alum Electrolytic; Cap 1 uF; Tol 20%; Vol-Rtg 50 VDC; Radial; 4x7; Bulk)
I will look into the the Kicad schematics but later since I have to download kicad and I need to learn how to use. So far, I have measured all pin voltage and the only thing that seems unusual is that Vin ~ 4.37v and 3.3v ~ 3.19v, I am using an ipod charger connected to one of the micro usb ports as you recommended. Also these are the measured nonzero (~ 0V) voltage values I recorded:
CanTx ~ 3.28v, DAC1 ~ 1.1v, DAC2 ~ 1.1v, A10 ~ 3.29v, A9 ~ 3.28v, A8 ~ 2.28v, A1 ~ 1.6v, A0 ~ 1.6v.
scl21 ~ 3.29v, sda20 ~ 3.29v.
Digital (pwm~):
0 ~ 2.99v 1 ~ 3.29v, 4 ~ 2.99v ... 0V.
vin ~ 4.37v, 5v ~ 4.9v, 3.3v ~ 3.19v, reset ~ 3.15v, IoRef ~ 3.19v.
That is all I can think of at the moment. Any word of advice on how to fix the SHIELD would be appreciated.
Best,
Felipe.