E-Scooter won't power up, LCD panel shorted - Page 1
Forum section: electronics / repair

author: Fallingwater
author_rank: Contributor
timestamp: September 20, 2022, 02:07:37 am
content: I was given a Cecotec Bongo A Advance Connected Max e-scooter (video in case you're curious: youtube NbePniFBxWk). A repair was previously attempted; they swapped out the controller, saw that it didn't work, gave up.I diagnosed it further and traced the issue to the LCD panel in the handlebars.Attached are a pic of the underside of the board, another pic of the underside with different lighting and a pic of the top sideThe motor controller and main power distributor seems functional: with the panel disconnected, when the on button is pressed it tries to apply +15V to the power rail that goes up to the LCD panel, but stops when the power button stops being pressed as it receives no serial communication from the panel itself. However, when the panel is connected the +15V supply rail from the controller is shorted to ground and, of course, nothing turns on.I *think* the issue might have been caused by incompetent assembly - the headlight's positive wire was mounted out of place and got squeezed enough that it might have shorted to ground through the frame. I traced the headlight pins to a SL6015-A9 LED driver on the board (marked U7, top-left in the pics); suspecting that I unsoldered it, along with a resistor on top that looked burned, and made very sure all the pads were clean. However, the power rail is still shorted to ground. I've desoldered, checked and resoldered in place the metal-can electrolytics and one of those big diodes since all three had the terminals shorted (I coloured everything I did in the last attached picture); they all tested good, and indeed the power rail kept being shorted without them.At this point I've run out of things I can try with no further help, as my experience with circuit design is extremely basic. I suspect another regulator (whatever gives +5V to the electronics from the +15V it's getting from the controller), but at this point it could be anything. It's got to be power- rather than logic-related, though - one single tiny component causing me all this headache.Can you help me? Where should I direct my attention now?To forestall the obvious question: no, a spare LCD panel is not available; what few shops should stock it don't.

author: fzabkar
author_rank: Super Contributor
timestamp: September 20, 2022, 02:47:55 am
content: U6, D2 and L2 appear to be a stepdown converter that provides the supply for the logic. The SoC (?) appears to have an additional inductor which may be part of its internal Vcore supply.I couldn't find a datasheet for the LED driver, but I can't see how any of its components could be the culprit.http://www.senliwell.com/product/172.htmlhttps://www.361shipin.com/blog/1564019944000061440

author: Fallingwater
author_rank: Contributor
timestamp: September 20, 2022, 10:44:12 am
content: Quote from: fzabkar on September 20, 2022, 02:47:55 amD2 checks good. I'll try to unsolder the others and see if the short disappears.QuoteWhere is that?QuoteIt isn't. I took it out and it's good. I suspected it due to the likely short on the LED wire and the overheated resistor, but it has no shorts once probed away from the board. As I said, my experience with this stuff is minimal.

author: fzabkar
author_rank: Super Contributor
timestamp: September 20, 2022, 05:44:35 pm
content: Quote from: Fallingwater on September 20, 2022, 10:44:12 amIt's adjacent to pin #9. What is the part number of the chip?