Haven't been very clear in my explanation, so let me summarize what we know so far:
Friday:
(1) U2 removed. U4B pin 5 grounded. U4B pin 7 and U4D pin 12 connected by soldering together pin 2 and 3 of U2 -> Oscillations
(2) U2 removed. U4B pin 5 grounded. pin 12 U4D grounded. pin 7 U4B grounded with a 10k (let's call it Rout). -> No Oscillations
Today:
(3) U2 removed. U4B pin 5 grounded. pin 12 U4D grounded. pin 7 U4B left open (no 10k Rout) -> Oscillations.
(4) U2 removed. U4B pin 5 grounded. U4B pin 7 and U4D pin 12 connected by soldering together pin 2 and 3 of U2. pin 7 U4B grounded with Rout -> No Oscillations
(5) U2 removed. U4B pin 5 grounded. U4B pin 7 and U4D pin 12 connected by soldering together pin 2 and 3 of U2. Bypass capacitor at pin 12 (soldered at the IC pin and ground via). I tried different values of C (e.g. 10nF, 470nF, 1u) -> Oscillations
UPDATE:
(6) U2 removed. U4B pin 5 grounded. trace coming out pin7 U4B cut as close as possible to the pin. race coming out pin12 U4D cut as close as possible to the pin. Connection between pin 7 and 12 with a short wire directly on the IC's pins -> Oscillations
(7) U2 removed. U4B pin 5 grounded. trace coming out pin7 U4B cut as close as possible to the pin. race coming out pin12 U4D cut as close as possible to the pin. pin12 of U4D to ground. pin7 of U4B with no load -> Oscillations
(8) U2 removed. U4B pin 5 grounded. trace coming out pin7 U4B cut as close as possible to the pin. race coming out pin12 U4D cut as close as possible to the pin. pin12 of U4D to ground. pin7 of U4B with Rout -> No Oscillations
Aaaaaa I feel we are getting close, but not just yet
Friday:
(1) U2 removed. U4B pin 5 grounded. U4B pin 7 and U4D pin 12 connected by soldering together pin 2 and 3 of U2 -> Oscillations
(2) U2 removed. U4B pin 5 grounded. pin 12 U4D grounded. pin 7 U4B grounded with a 10k (let's call it Rout). -> No Oscillations
Today:
(3) U2 removed. U4B pin 5 grounded. pin 12 U4D grounded. pin 7 U4B left open (no 10k Rout) -> Oscillations.
(4) U2 removed. U4B pin 5 grounded. U4B pin 7 and U4D pin 12 connected by soldering together pin 2 and 3 of U2. pin 7 U4B grounded with Rout -> No Oscillations
(5) U2 removed. U4B pin 5 grounded. U4B pin 7 and U4D pin 12 connected by soldering together pin 2 and 3 of U2. Bypass capacitor at pin 12 (soldered at the IC pin and ground via). I tried different values of C (e.g. 10nF, 470nF, 1u) -> Oscillations
UPDATE:
(6) U2 removed. U4B pin 5 grounded. trace coming out pin7 U4B cut as close as possible to the pin. race coming out pin12 U4D cut as close as possible to the pin. Connection between pin 7 and 12 with a short wire directly on the IC's pins -> Oscillations
(7) U2 removed. U4B pin 5 grounded. trace coming out pin7 U4B cut as close as possible to the pin. race coming out pin12 U4D cut as close as possible to the pin. pin12 of U4D to ground. pin7 of U4B with no load -> Oscillations
(8) U2 removed. U4B pin 5 grounded. trace coming out pin7 U4B cut as close as possible to the pin. race coming out pin12 U4D cut as close as possible to the pin. pin12 of U4D to ground. pin7 of U4B with Rout -> No Oscillations
Aaaaaa I feel we are getting close, but not just yet
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