Voltage Sequence Chart Shoaib October 02, 2025 Voltage Sequence Chart (1–35) Voltage Sequence Chart (Steps 1–35) Search Highlight generation — All — 1st Gen (Arrandale) 2nd/3rd Gen (Sandybridge/Ivybridge) 4th/5th Gen (Haswell/Broadwell) 6th–10th Gen (Skylake/Kabylake/Whisky/Coffee/Comet) 10th/11th Gen (Icelake/Tiger Lake) 12th Gen (Alder Lake) Legend: value = rail present, X = not used / N.A., * = vendor-specific naming. 1st Gen 2nd/3rd Gen 4th/5th Gen 6th–10th Gen 10th/11th Gen 12th Gen SL 1st GenArrandale 2nd/3rd GenSandybridge/Ivybridge 4th/5th GenHaswell/Broadwell 6th–10th GenSkylake/Kabylake/Whisky/Coffee/Comet 10th/11th GenIcelake/Tiger Lake 12th GenAlder Lake 1RTC_VCCRTC_VCCRTC_VCCRTC_VCCRTC_VCCRTC_VCC 2XXXTBT_VBUS 5VTBT_VBUS 5VTBT_VBUS 5V 3XXXTBT_LDO 3.3V/1.8VTBT_LDO 3.3V/1.8VTBT_LDO 3.3V/1.8V 4XXXCHG_VIN_20V/SDC_INCHG_VIN_20V/SDC_INCHG_VIN_20V/SDC_IN 519V19V19V/13V*19V/13V*19V/13V*19V/13V* 63.3V ALW3.3V ALW3.3V ALW3.3V ALW3.3V ALW3.3V ALW 75V ALW5V ALW5V ALW5V ALW5V ALW5V ALW 815V ALW*15V ALW*15V ALW*XXX 919VSB (COMPAL)*19VSB (COMPAL)*19VSB (COMPAL)*XXX 10XXX1.8V ALW1.8V ALW1.8V ALW 11XXXXVCC1.05_OUT_PCHVCC1.05_OUT_PCH 12XXXXVCC1.05_OUT_FETVCC1.05_OUT_FET 13XXX1V ALW1.8V VCCIN_AUX1.8V VCCIN_AUX 14XX3.3V PCH (COMPAL)*3.3V PCH (COMPAL)*3.3V PCH (COMPAL)*3.3V PCH (COMPAL)* 15XX5V PCH (COMPAL)*5V PCH (COMPAL)*5V PCH (COMPAL)*5V PCH (COMPAL)* 16XXX1V VCCST1V VCCST+1.05V_PROC 17XXX2.5V VPP2.5V VPPX 18XXXXX5V_VDDQ 191.5V VDDQ1.5V VDDQ1.35V VDDQ1.2V VDDQ1.2V VDDQ1.1V CPU_VDDQ 203.3V VS/S03.3V VS/S03.3V VS/S03.3V VS/S03.3V VS/S03.3V VS/S0 215V VS/S05V VS/S05V VS/S05V VS/S05V VS/S05V VS/S0 22XXX1V VCCIO1.05V VCCIO*X 23XXX1V VCCSTG1V VCCSTGX 24XXX1.8V S0*XX 25XXX1.2V S0*1.2V S0*X 261.5V_CPU_VDDQ1.5V_CPU_VDDQXXXX 271.8V S01.8V S01.8V S0XXX 28X1.5V S0*1.5V S0*XXX 291.05V PCH CORE*XXXXX 301.05V VTT/VCCP1.05V VTT/VCCP1.05V VTT/VCCPXXX 310.75V RAM VTT0.75V RAM VTT0.67V RAM VTT0.60V RAM VTT0.60V RAM VTTX 32XVCCSAXVCCSAXX 33GFX COREXXXXX 34CPU CORECPU CORECPU CORECPU CORE (VCCIN)CPU CORE (VCCIN)CPU CORE (VCCIN) 35XGFX COREXGFX CORE (VCC_GT)GFX CORE (VCC_GT)GFX CORE (VCC_GT) Voltage Sequence Chart (1–35) Voltage Sequence Chart (Steps 1–35) Search ... Read more »
Dell 14-3478 EC Firmware Mystery Resolved by BIOS Update Shoaib June 06, 2025 🧠 When the Dead Came Back to Life: A Dell 14-3478 EC Firmware Mystery Resolved by BIOS Update Date: [Insert Today’s Date] Category: Laptop Repair Case Study Model: Dell Inspiron 14-3478 Board Number: 17841-1 Issue: No Power, Missing PCH_PLTRST#, Random Auto Boot Resolution: EC Firmware Recovered via BIOS Update 🛠️ The Problem A Dell Inspiron 14-3478 landed on my desk with an intermittent no power issue. Most of the time, pressing the power button did nothing. Sometimes, it would turn on by itself (no button press), run perfectly, and then next time go dead again. I started troubleshooting the classic power-on sequence. Here's what I found: SYS_PWROK — Present (3.3V) PCH_PWROK — Present (3.3V) PROCPWRGD — Missing (0V) PCH_PLTRST# — Missing VR_RDY — Initially fluctuating; fixed by installing missing pull-up resistor PR4609 🔍 The Investigation I traced the PROCPWRGD signal back through the schematic and found it’s generated by the EC (Embedded Controller): EC Model: MEC1416 Output Pin: GPIO057 (VCC_PWRGD) With ALL_SYS_PWRGD and VR_RDY both confirmed present, the EC should have asserted PROCPWRGD, but it didn’t. Additional symptoms: EC firmware corruption suspected PCH getting hot (PLTRST# missing) Random auto-boot behavior 💡 The Breakthrough I remembered that Dell BIOS EXE updates often include EC firmware. So when the laptop randomly turned on, I launched the official BIOS update executable. Result: PROCPWRGD — Present PCH_PLTRST# — Present CPU VCORE — OK System now turns on every time 🧠 Root Cause The EC firmware was partially corrupted. That’s why: It sometimes booted correctly Sometimes didn’t assert PROCPWRGD BIOS update fully re-flashed EC and resolved the issue 🔁 Firmware Behavior Flow Diagram: ✅ Lessons Learned Suspect EC firmware if PROCPWRGD, PLTRST# are missing Random behavior often means firmware corruption, not hardware fault BIOS update via EXE is a fast way to recover EC if system can turn on 🧰 Tools Used Multimeter CH341A programmer (for backup plan) Dell official BIOS updater (.exe) 📌 Final Words This case reminded me why timing is everything in laptop repair. I used the brief moment the laptop powered on to flash the BIOS and restore the EC. If I had missed it, this board could’ve been written off as dead. Next time your system plays dead — wait... it might come back to life just long enough for you to save it. 💬 Have you faced something similar? Drop your experience in the comments below! 🔧 Follow more case studies at bdfixforum.blogspot.com 🧠 When the Dead Came Back to Life: A Dell 14-3478 EC Firmware Mystery Resolved by BIOS Update Date: [Insert Today’s Date] Category:... Read more »