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So, in my latest experiment with an 8 feather DVI board, I was greeted with a strange smell and a board that stopped working flat. After some hair-raising debugging, I discovered that our villain might be a dodgy Voltage Regulator, throwing a tantrum and refusing to output voltage steadily. After removing it, I conscripted an external 3.3 volt regulator and voila! The board sprang back to life, and we have a happy ending. But the mystery continues: what wreaked havoc in the first place? I'm pinning the blame on a rebellious USB hub. So, next on the agenda, shopping for a new hub before it sends another board to its early grave.

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[0:00] so I’ve been doing some experiments with
[0:02] this um 8 feather DVI board it was all
[0:05] going really well until there was a
[0:07] slightly strange smell and then it
[0:08] stopped working so uh one of the
[0:11] symptoms if we um plug in USB Supply
[0:15] then what I can see Got 5 Vols coming in
[0:19] and on the 3.3 volt
[0:21] line we have nothing at all now I’ve
[0:25] looked at the schematic this chip here
[0:27] is the voltage regulator this should be
[0:30] the output pin and uh there nothing on
[0:33] that but we are definitely getting 5
[0:36] Vols coming into it slightly awkward to
[0:38] probe because of the battery connector
[0:40] yeah 4.9 volts now the enable pin is pin
[0:43] two this should be held high and that’s
[0:47] pretty much zero volts so suspect this
[0:50] IC might be a bit dead let’s do a bit
[0:53] more
[0:56] probing beeper mode so what we can see
[0:59] if we TR the 3.3 volt rail is we got a
[1:03] dead short and if we look at this IC if
[1:07] we look at the enable
[1:09] pin that’s also a dead shot so that
[1:13] leads me to think this IC has gone a bit
[1:16] wonky so what I’m going to do is I’m
[1:18] going to remove that and I’ll try just
[1:20] powering it with an external 3.3 volt
[1:22] Supply see if the board bring us back
[1:24] into life um there’s quite a lot of
[1:27] plastic to cover up here so I got a bit
[1:29] of cap on tape and do that and then get
[1:31] the hot air gun out and remove that chip
[1:33] so hopefully that’s nicely protected uh
[1:36] let’s get the hot air gun on and remove
[1:38] this um IC so quick plug to PCB way who
[1:41] sponsored the channel so I’ve currently
[1:43] got my new ESP Spectrum Boards out with
[1:45] them at the moment being manufactured
[1:47] and I’m just playing around with options
[1:48] for output to a bigger screen so thanks
[1:51] to PCB for sponsoring the channel
[1:53] looking forward to getting the new
[1:53] boards back
[1:56] [Applause]
[2:15] okay that was fairly painless um it’s
[2:19] good let’s uh let’s see if our shorts
[2:21] have actually disappeared
[2:24] so let’s get the multimeter back in
[2:32] so let’s see on our 3.3
[2:35] volt the Short’s gone that’s good and on
[2:39] the enable pin shorts also
[2:43] gone so what I’m going to try and do we
[2:46] got this nice little uh voltage
[2:49] regulator here 3.3 volts so what I’ll do
[2:53] is I’ll try this on some breadboard and
[2:55] see if we can power the 3.3 line
[2:57] externally
[3:01] well that actually worked that’s it
[3:03] that’s very pleasing so what I’m going
[3:05] to do is I’m just going to it’s a bit
[3:06] annoying having to have this on
[3:07] breadboard um so what I’ll do is I’ll
[3:10] just wire up some little wires to this
[3:14] and then um sold it onto the board so
[3:17] let’s get that done
[3:20] [Music]
[3:31] that’s surprisingly
[3:33] hot let’s try that
[3:38] [Music]
[3:44] again okay I’ve Soldier some wires on
[3:47] not the neatest soldiering job now we
[3:50] just need to connect these on to the
[3:51] appropriate pins on our um on our board
[3:55] so let’s give that a go
[3:58] [Music]
[4:28] yeah that’s probably not bad that should
[4:30] work
[4:32] um let’s
[4:34] check see if we get 3.3 volts where we
[4:37] expect
[4:39] it or do we just get magic
[4:45] smoke 3.3 volts brilliant plug this in
[4:49] and see if it actually does work okay
[4:51] the board’s plugged in and have a look
[4:53] at
[4:54] this there we go DVI output working
[4:58] nicely brilliant it’s fixed so one
[5:01] question is what actually killed the
[5:03] board in the first place so I’m
[5:05] beginning to suspect that it was this um
[5:07] USB hub so I’ve been using this to hook
[5:10] up a keyboard to the um to the feather
[5:13] and it does behave extremely
[5:15] automatically when it’s plugged in so I
[5:18] think I might uh find a different USB
[5:20] hub for these experiments because I
[5:23] can’t really afford to keep blowing up
[5:24] boards

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Chris Greening

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A collection of slightly mad projects, instructive/educational videos, and generally interesting stuff. Building projects around the Arduino and ESP32 platforms - we'll be exploring AI, Computer Vision, Audio, 3D Printing - it may get a bit eclectic...

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