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AMD Geode/Video 3/Script
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== Lessons learned == Narrator: "Okay we're done. Let's talk about some of the lessons learned." A glossy green slide shows the text "Lessons learned" Narrator: "First, make a plan when soldering. Practice on e-waste to see if it's something you can do. Take breaks throughout and assess the situation. I didn't do any of these and I damaged the board." A glossy green slide shows the the following text: * Lesson 1: Have a plan * Practice it on e-waste * Take breaks * Assess the situation * I didn't do these and failed Narrator: "Secondly, understand the circuit properly! Had I done this I wouldn't have even had to solder the board." A glossy orange slide shows the the following text: * Lesson 2: * Understand the circuit! * I could've avoided disaster altogether Narrator: "Let me explain: In part 1 I drew this diagram" A picture of the circuit board near the CPU is shown. Text and lines are drawn over it, forming a diagram that shows: * DAVdd connects to the LM4041AIM3-1.2 voltage reference * From the 1.22 volt reference a 0.25 nanofarad capacitor and 10 kiloohm resistor in parallel run to DVREF * The 1.21 kiloohm resistor follows from the DVREF capacitor and resistor to the DRSET pin In the top left the text "I drew this:" is shown. Narrator: "I then measured these voltages" The diagram is updated. DAVdd is marked as 3.3 volts, DVREF is 1.22 volts and DRSET is 40 millivolts. In the top left the text "I measured:" is shown next to the voltages. Narrator: "How is DAVdd 3.3 volts if it's connected to a 1.2 volt reference?" The voltage reference's 1.2 number is circled. The text "DAVdd should be 1.2v not 3.3v!" is shown. Narrator: "How is DVREF 1.22 volts using this voltage divider?" The two resistors are circled. The text "This voltage divider doesn't add up" is shown. The 10k resistor is circled instead. Narrator: "It makes no sense!" Three giant question marks are shown overlaid the diagram. Narrator: "When it comes to the part of the board I spent time troubleshooting and soldering, it gets worse!" A picture of the circuit board near is shown, near the VGA output port. It contains various surface mount chips, but in the center is a set of 3 small capacitors, 7 inductors, 3 ESD diodes and 7 resistors. The text "It gets worse with the video circuit!" is overlaid. Narrator: "I thought this circuit had the video signals travelling through capacitors, through inductors, through these ESD diodes, and out through these termination resistors." Text overlays the diagrams labels the capacitors, inductors, ESD diodes and resistors. The top three capacitors are labelled R, G and B. Three separate lines from each of these capacitors draw through a set of inductors, ESD diodes and resistors. The lines are coloured red, green and blue. Narrator: "I figured that an ESD diode was faulty, pulling a signal line down to GND. This would cause a low voltage." The text "Would a bad ESD diode pull the signal low?" is shown. The green line is replaced with a shorter line that ends at one of the pins of its ESD diode. Narrator: "Had I just measured the ESD diodes with my multimeter in resistance and diode mode I could've ruled this out." A cartoon multimeter is shown with its black probe on the GND pin of the ESD diode and the red probe on the signal pin of the ESD diode. The text "Measuring resistance or diode drop would have shown me the diodes were working correctly" is shown. Narrator: "Even then, I decided to remove the capacitors to isolate the signals" The circuit board is shown again, this time with the top capacitors removed. The red, green and blue lines stop at the signal side of the capacitor and no longer flow to the inductors. The text "I removed the capacitors to rule out any fault..." is shown. Narrator: "But these are connected to GND, not the signal!" The red, green and blue lines turn to crossed out stubs. The text "But they weren't connected to the signal!" is shown. Narrator: "Removing them would not show the fault at all! I was doomed from the start." The red, green and blue lines start again at the inductors and flow to the resistors again. Except for green which is shown flowing to the GND side of its ESD diode.
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