Identifying a missing part with no schematic, board layout, or similar board. - Page 1
Forum section: electronics / repair

author: PoDuck
author_rank: Regular Contributor
timestamp: September 19, 2018, 02:22:11 am
content: I have something that is rather annoying on my bench right now. It's a 5th gen iPad that came to me with an obvious tristar chip fault. In the process of removing the chip and cleaning the pads though, I displaced a component next to the chip, and I can't find it to replace it, and I can't find a schematic or board layout for this specific model iPad, but I have schematics and board views for pretty much every other iPad. Considering I had no choice at the time, I decided to risk that it was a filter cap and put the device back together to only get a boot loop. This suggests to me that it was likely a resistor or a diode, and something isn't getting power that should be.Here's my thinking so far. Looking at the layouts of other iPads and iPhones, the components that surround tristar are almost all capacitors. Some have only a couple zero ohm resistors, and some have a bunch of zero ohm resistors. About half seem to have a single diode in the area. None have a resistor with any value higher than zero. So, I'm thinking that the chances are pretty good that I knocked off a zero ohm resistor, but if I'm wrong, and it should have been a diode, I worry I might kill something, possibly something important. On the other hand, if I put a diode in there, it is possible that it will still work, but is also possible that it could blow, which might have a chance of blowing the pad out, causing me to swear profusely.Would it be safer to try a diode or a resistor in the spot, or does someone have a better method of figuring out what the component should be?

author: Mario87
author_rank: Frequent Contributor
timestamp: September 19, 2018, 08:15:07 am
content: First thing, is can you post a picture of the affected area and another picture zoomed in on the missing component? With pictures it may allow someone to see exactly which part you are referring to and provide you with an answer as to what the part is meant to be.

author: PoDuck
author_rank: Regular Contributor
timestamp: September 19, 2018, 08:41:40 pm
content: Looking at it today, it appears I might have kicked off three components. On this image, there are two on the top left and one on the bottom right. The one on the bottom right is the one I was first noticing.

author: Richard Crowley
author_rank: Super Contributor
timestamp: September 19, 2018, 08:45:44 pm
content: Louis Rossman seems to be able to source schematics and board layout diagrams for most everything he works on.Are you using a similar source for 3rd party documentation like he is?He has been hassled by Apple lawyers for revealing the sources of this info, so he doesn't seem to share it openly.

author: PoDuck
author_rank: Regular Contributor
timestamp: September 19, 2018, 11:56:35 pm
content: I have both ZXW Tool and Easy Draw, both are similar in function, although not as good by a long shot, as Paul Daniels board view software, and they come with all the schematics and board views I know about for iPads and iPhones. It has all the iPad versions besides the iPad 5, unfortunately.