Repairing a "for parts" Canon 7D Mark II.<br>Posts<br>HP 8640B2. Mains input and rectifier board replacement<br>1. Initial state

Wireless tallyPart 1: intro<br>Part 2: nearly finished<br>Part 3: Xbee part numbers

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Repairing a "for parts" Canon 7D Mark II.

Tuesday, March 4, 2025 | 10 minutes

Canon 7D Mark II<br>Repair

Update (06/11/2025): I found out that &ldquo;**names_are_hard**&rdquo; is the lead developer behind Magic Lantern, added that information in-line. Also fixed a typo.

Introduction<br>I was recently looking for a replacement for my ageing (ancient?) entry level Canon 600D. I came across a cheap 7D Mark II body (7d2 from now on) that was sold as &ldquo;broken, for parts only&rdquo;. This repair was a fun and rewarding experience requiring no spare parts.<br>The Canon 7D Mark II<br>The Canon 7D Mark II is a high-end 20.2 megapixel APS-C size DSLR that was released towards the end of 2014. It is part of their advanced/professional range of cameras and could be regarded as similar to a 5D Mark IV with a smaller CMOS. At the time of release it was positively received. The body I purchased was sold for €180 as &ldquo;broken, for parts only&rdquo;. Let&rsquo;s hope not.<br>Initial checks<br>The body arrived as described by the eBay seller: in good cosmetic condition but broken.<br>The camera would start up without anything on the LCD.<br>Pressing the shutter halfway would not trigger the autofocus but pressing it all the way would cause it to take a picture.<br>No output on the HDMI connector.<br>Dmesg would not show anything after making a USB connection.<br>Manually forcing the camera to autofocus by pressing the matching button would cause the lens to refocus.<br>Interestingly, when powering off the camera, it would display the &ldquo;cleaning the sensor&rdquo; image. Clearly the LCD and the driver were functioning to some extent.<br>I suspected that &ldquo;somehow&rdquo; the processor evaluated the shutter button as half-pressed the whole time. When simulating this with my 600D, I got similar behaviour: a black LCD, no autofocus but possible to take pictures. Not exactly a perfect test, but promising.<br>Searching online, I found references to grains of sand getting stuck between the button and the outer shell. However, this seemed mostly related to some other cameras, not the 7d2. Would it be as simple as a small particle blocking the button? While the 7d2 has weather sealing, it was quite possible for small particles to cause mechanical issues at some places&mldr;<br>Disassembly<br>I found a parts list describing the position and size of all the screws, definitely helping reassembly afterwards.<br>Even though I &ldquo;kind of&rdquo; knew what to expect, I kept being surprised by even more flex circuits, time after time. There are two types:<br>FFC (Flexible flat cables) are a type of very thin, light and flexible plastic (usually Polyimide or Polyamide) films with embedded conductive traces. They are used as interconnects, replacing conventional cables and connectors. An additional benefit is that it is possible to embed multiple controlled impedance connections on one connection. While more complicated to manufacture, their properties make them a very versatile alternative. See this Molex product page.<br>FPC (Flexible printed circuits) are similar, but somewhat resemble PCB&rsquo;s in that they not only contain traces, but also components. More on them on this page from Dexerials.

Many flexible things

A couple of hints:<br>The rubberized grips come of easily and no additional glue is needed afterwards to stick them back on.<br>While the parts list tells you which screw goes where, seeing the difference between M1.7 and M2 screws is rather difficult. Don&rsquo;t rely on the the list alone and document the origin of screws.<br>The main PCB alone has 19 (!) connectors. Be careful as some are easily damaged and -unless you are lucky- you will need to (dis)connect them more than once.

Troubleshooting<br>At this point, I decided to put a post on the Magic Lantern Discord to describe my symptoms and ask if this behaviour was a known issue. While my issue was not related to Magic Lantern, this group of people likely have the best knowledge about the inner workings of all things Canon DSLR 1. Maybe they wouldn&rsquo;t mind.<br>They did not. At all. Almost immediately I got advice and questions from Walter Schulz,...