Fix iPhone 7/7 Plus Can Not Turn On - CPU Repair

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<p><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">iPhone 7/7 Plus won&#39;t turn on after it is dropped? Due to the imperfect technology of CPU supplier, the SDRAM of iPhone 7/7 </span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Plus&nbsp;</span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">series</span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;"> can be easily damaged. Once dropped, the SDRAM might be </span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">short-circuited</span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;"> and the phone won&#39;t turn on afterward. Let&#39;s&nbsp;click the video&nbsp;to&nbsp;know</span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">&nbsp;how we fix iPhone 7 plus won&#39;t power on </span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">the issue</span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;"> in a more efficient way.</span></p><p><br/></p><p><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Diagnosis</span></p><p><br/></p><p><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Take apart the phone and disconnect the battery, then connect the phone with the DC Power Supply and press </span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">power</span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;"> button to power on. The current reading of the ammeter jumps to 350mA and then stays still, which is abnormal and indicates that the logic board is </span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">short circuited</span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">.</span></p><p><br/></p><p><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Disconnect the power supply and take out the logic board. Run diode measurements on capacitors around power IC one by one. All the values are normal except&nbsp; C1823 – It displays 0, which indicates that C1823 is short-circuited. From the schematics, we can see that C1823 is the filter capacitor of PP1V8-SDRAM, and it is directly connected to CPU SDRAM.</span></p><p><br/></p><p><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Attach the logic board to the PCB Holder, and take down the shielding cover by heating with Hot Air Gun, then remove CPU SDRAM with CNC Chip Grinding Machine. After chip grinding, attach the logic board to the PCB Holder and clean it with PCB Cleaner, then remove the black adhesive around with Sculpture Knife. After that, apply some BGA Paste Flux to the bonding pad. Align the new SDRAM to the right place(Don’t reverse the direction),&nbsp; and then solder with Hot Air Gun. After cooling for 5 minutes, clean thoroughly with PCB Cleaner.</span></p><p><br/></p><p><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Testing</span></p><p><br/></p><p><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Connect the phone with the DC Power Supply, then short Pin 13 of J4504 to the ground with </span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">tweezer</span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;"> to trigger the power on </span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;" class="gr-progress">system</span><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">. This time, the current reading on the ammeter is normal.</span></p><p><br/></p><p><br/></p><p><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Get the logic board assembled and buckle the display assembly. Connect the phone to the computer, then press and hold volume down and power button to get into DFU mode. Restore the phone via iTunes. Once done, insert the SIM card and activate the phone. After testing, All the functions work normally.</span></p><p><br/></p><p><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">If you want to see the detail by pictures&nbsp;please&nbsp;go to </span><a href="http://blog.rewatechnology.com/fix-iphone-7-wont-power-on-cpu-repair/" target="_self" style="text-decoration: underline; color: rgb(0, 176, 240); font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;"><span style="color: rgb(0, 176, 240); font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">REWA Blog</span></a><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">.&nbsp;<span style="color: rgb(102, 102, 102); font-family: Roboto, Arial; text-align: justify; background-color: rgb(255, 255, 255);">&nbsp;We have published&nbsp;&nbsp;</span><a href="https://www.rewatechnology.com/Fix-iPhone-6s-will-not-Turn-On-PMIC-Grinding-and-Replacing.html" target="_blank" rel="noopener" style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; line-height: inherit; font-family: Roboto, Arial; vertical-align: baseline; -webkit-font-smoothing: antialiased; text-decoration-line: none; cursor: pointer; color: rgb(26, 26, 26); display: inline-block; transition: all 200ms ease-out; text-align: justify; white-space: normal; background-color: rgb(255, 255, 255);"><span style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; font: inherit; vertical-align: baseline; -webkit-font-smoothing: antialiased; display: inline-block; color: rgb(0, 0, 255);">iPhone 6 won’t turn on</span></a><span style="color: rgb(102, 102, 102); font-family: Roboto, Arial; text-align: justify; background-color: rgb(255, 255, 255);">&nbsp;and&nbsp;</span><a href="https://blog.rewatechnology.com/iphone-x-wont-turn-on/" target="_blank" rel="noopener" style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; font-variant-numeric: inherit; font-variant-east-asian: inherit; font-stretch: inherit; line-height: inherit; font-family: Roboto, Arial; vertical-align: baseline; -webkit-font-smoothing: antialiased; text-decoration-line: none; cursor: pointer; color: rgb(26, 26, 26); display: inline-block; transition: all 200ms ease-out; text-align: justify; white-space: normal; background-color: rgb(255, 255, 255);"><span style="box-sizing: border-box; margin: 0px; padding: 0px; border: 0px; font: inherit; vertical-align: baseline; -webkit-font-smoothing: antialiased; display: inline-block; color: rgb(0, 0, 255);">iPhone X won’t turn on&nbsp;</span></a><span style="color: rgb(102, 102, 102); font-family: Roboto, Arial; text-align: justify; background-color: rgb(255, 255, 255);">guide video</span></span></p><p><br/></p><p><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Tools Used:</span></p><p><a href="http://www.rewatechnology.com/dc-power-output-pen-10868.html" target="_self" style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;; text-decoration: underline;"><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">DC Power Supply</span></a></p><p><a href="http://www.rewatechnology.com/digital-multimeter-type-3-13472.html" target="_self" style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;; text-decoration: underline;"><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Digital Multimeter</span></a></p><p><a href="http://www.rewatechnology.com/integrated-mobile-phone-repair-platform-red-12601.html" target="_self" style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;; text-decoration: underline;"><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Integrated Mobile Phone Repair Platform</span></a></p><p><a href="http://www.rewatechnology.com/pcb-holder-for-iphone-repair-15038.html" target="_self" style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;; text-decoration: underline;"><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">PCB Holder</span></a></p><p><a href="http://www.rewatechnology.com/rewa-cnc-chip-grinding-machine-12927.html" target="_self" style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;; text-decoration: underline;"><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">CNC Chip Grinding Machine</span></a></p><p><a href="http://www.rewatechnology.com/screwdriver-for-iphone-middle-plate-type-1-10876.html" target="_self" style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;; text-decoration: underline;"><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Screwdriver</span></a></p><p><a href="http://www.rewatechnology.com/solder-wick-2015-12226.html" target="_self" style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;; text-decoration: underline;"><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;;">Solder Wick</span></a></p><p><span style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;; text-decoration: underline;"><a href="http://www.rewatechnology.com/100g-solder-wire-type-1-10836.html" target="_self" style="font-family: 微软雅黑, &quot;Microsoft YaHei&quot;; text-decoration: underline;">Solder Wire</a></span></p><p><br/></p><p><br/></p><p><br/></p>