Dock only - no LCD - How i fixed one of those today

Thought I’d share this as it might be useful to other people.

I got a switch today that would only display when docked. Stripping the motherboard out I noticed the LCD connector had a few bad pins so I swapped that but still the same.

Next I inspected the board and found to 2 caps(?) near the Pi3USB to be snapped in half so I replaced those but still no LCD display.

I then spent a bit of time measuring around the Pi3USB but couldn’t find anything out of the ordinary so after looking at the Pi3USB datasheet I thought it might be a problem with the control of the Pi3USB IC and swapped out the cap(?) that is attached to pin 1 and that fixed the issue.

i probably spent 4 hours trying to figure this out so maybe this will be helpful to someone else. in the picture below 1 and 2 are the snapped caps and 3 is the cap that i replaced to bring the LCD back to life.

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Thanks for sharing your findings …

Btw where are the CAD drawings from? Self generated ? or available publicly? :slight_smile:

I stole them from calvin when he posted them on here :slight_smile:

Just curious. How did u know to replace cap 3? Was the diode reading off? Thanks

the Diode seemed fine but looking at the datasheet for pin 1 of the Pi3USB IC it is listed as Mode. I’m not 100% sure but I believe when the switch is docked and undocked this pin gets a signal to enable or disable video to the dock.

Thanks for the info.

I got a switch that docks for 15 seconds and then goes black. Plays in handheld fine. All measurement looks normal so I will give it a shot and replace this.

May i ask what value those cap in number 3?, just for reference in case i encounter this kind of case. Thanks

According to the datasheet from the PI3USB the Value for this cap on pin 1 (Mode) should be 4.7kOhms.