Yose Power Display (KD21C) won't stay powered up

sloth1

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Aug 16, 2022
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I recently had a problem with my Yose Power Ebike kit where the display suddenly failed to stay powered up.
The symptoms were that upon pressing the power button for 2 seconds, the display would come on but the battery level indication on the display was flashing as Empty (even with a full battery).

As soon as the power button was released, the display would power off.

Keeping the power button pressed for long enough eventually gave an "Error 30" (communication error).

I suspected that the display had a fault and so purchased a new one. The new display immediately behaved correctly and so, although I'd sorted the problem I wondered if the old display could be fixed.

The answer was YES and so I thought I'd share my findings here for other users.

Getting the display apart requires some patience. Using a knife, carefully press into the seam just enough to get an old credit card into the gap, use the credit card to open up the seam all the way around. Do not slide the knife down the side of the display because this may cut the flexible cable to the display.
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Once the display has been carefully cut all the way round it is possible to separate the front bezel from the back of the display.
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Two retaining screws can be removed to loosen the circuit board. There are two plastic lugs which also need to be trimmed off so that the circuit board can be removed. Use a static safe mat and wrist strap when removing the circuit board to prevent causing damage to the sensitive circuitry.
20220803_085155.jpg

Carefully inspect the PCB for solder joints, in my case the pin shown was not soldered correctly and had become detached due to vibration.

Using a fine tipped soldering iron, carefully re-solder any such connections.

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Re-assembly is the reverse process.

It will be necessary to carefully re-glue the front bezel back onto the display. Unfortunately the display will not be water proof unless the bezel is glued on properly.

Obviously any manufacturer warranty is voided by implementing this fix

I hope this helps others out there who encounter the same issue.
 
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