Hypothetical Scenario

[macacob]

If one were to solder the TL072 backwords, and then install it in a C64 and turn it on, what other components of the SKPico with onboard DAC might get fried? Asking for a friend. (Thankfully no damage to the C64)

[frntc]

Hm... I have no empirical values ;-) I think there's a good chance that only the TL072 is damaged. Have you tried replacing it (it's probably fried, at least you, well your friend, swapped +5V and GND)

[macacob]

That was my first guess as well after looking at the schematics of the TL072. I desoldered it and replaced it with a new one. I was able to get to the menu but no sound through PWM (I did solder the jumper to allow the DAC model to play through PWM, I made that mistake on my first build). I have gone back over all of my soldering work and reflowed everything and it looks clean. I have more to build so I'll probably set this one aside for now but and build those more carefully, but it drives me nuts not knowing why something isn't working.

[frntc]

You need to take the DAC-firmware, there's no PWM sound on this one! The opamp is there to drive the audio through the mainboard :-)

[macacob]

Hmm, good suggestion. I will go back and triple check what I installed on the pico, but I am 99% sure it is the same firmware I have on prior builds which are working.

[macacob]

Soooo, both the SKPico board and the Pico clone board are faulty. the RGB Pico clone does not work with my known good SKpico build, and my known good RGB Pico clone will not work with my faulty SKpico build. not a firmware issue I guess, something really did get damaged.