I'm hoping today's video turns out okay cause I'm a little under the weather
I got some hot tea and some fisherman's friends just to try and keep
me from coughing in your ear what I'm doing yeah it's taking a look at this
the dynex KVM keyboard video mouse switch basically it's got two outputs to
the computer there are two two different computers to monitor and put some two
different computers and then one monitor output and then a USB hub on the front and
the A-B switch on the top so it basically lets you connect two computers up to one
Mouse and monitor and keyboard setup pretty straightforward usually there's
larger versions of these that get used in like data center so they got a whole
rack full of servers and they just want to share them with one monitor and
keyboard this one's a little bit smaller one this is one that I found in the box
of IT junk in the corner at work that hasn't been used for a couple of years
so I figured I could probably borrow it before somebody threw it out
unfortunately when we were hooking it up in the kids room to his slowly growing
computer lab that he's building in there it's a teenager thing I guess yeah I've
got two computers within arm's reach for me so maybe it's just a living in this
house thing anyway so he had this thing hooked up and it seemed to be working
and then we plug in the power supply that was with it when I got it and the
mouse that was plugged into this specifically this fancy gaming mouse
immediately stopped working it's got a little LED thing in there and that
stopped working as well so we quickly unplugged everything and stuck my nose
up to this thing and sure enough she got the smoke out
not pleased about that so I'm guessing well so this this power pack it's rated
for 12 volts 500 milliamps and it was in the in the bag or in the box with this
thing when I pulled it out of the IT closet the bottom of this has no
information at all it doesn't say what its voltage is anything else no not even
a model number and searching around online I can only find like a eBay
listing for somebody selling one of these with no power supply Dynex's
website seems to be an alias for Best Buy's website so I'm guessing that's
their house brand but anyway I guess the first thing to check is what is this
power supply doing so this power supply claims to be twelve volts but in reality
with no load on it it's like seventeen point nine that's a little carried away
OK now, a one K load on it that's still almost 17 volts so that's probably ow
that resistors warm so it was drawing a fair bit of power that's probably a
pretty good clue as to why this thing let the smoke out so I got the cover off
it and just looking inside here looks like there's some power steering diodes
so that this thing doesn't back feed down from the power connector to the
output so first thing I'm guessing this thing is probably only expecting five
volts off the wall wart maybe six minus a diode drop right that's a little
disturbing so the we just go to sniff test and
sound smells like it's coming from down this
end and that's sort of what I expect experience to kind of smell that was
coming from that connector let's see if we can see the skid marks or anything
oh that chip over there looks like it's not super happy there's that just a bit
of Fox no I can feel that's that little shiny spot there is actually three
dimensional so I think that guy probably was on was heating up so the 74 HC 244
is a an octal buffer one driver tri-state so it's its outputs can either
be go high low or be it a floating don't care a kind of a level so eight lines
and there's two of them in there so we're basically controlling 69 so I'm
guessing that those are probably switching the video the VGA ports so
there's what it is inside and there's two control lines to switch them order
to switch the outputs from there don't care to their pass-through kind of mode
aha here we go supply voltage Max Plus seven of volts that would explain what
happened when you put 17 volts on it I guess I could have figured this out from
looking at the board too but it confirms what my guess was these two eight port
wine drivers do you have a bunch of traces that are going to the VGA
connections so that's not really a surprise the USB magic is happening
under a lab lob that is a SIL resistor so pulling up probably I'm guessing no
no that's the ground point so it's the sill resistor is pulling pulling the USB
lines down okay and where is there's our output
where's that little 6-pin there oh that's a switch
what is the USB just being mechanically switched because this is the this is the
two USB outputs to the two different computers and there's to Des Moines
there and there's two data lines there
yeah they're just coming over to this fricking switch oh and then they're
going through this which is a USB hub probably and then out to these four guys
okay so that's that's pretty low-rent
let's just try a little experiment here shall we my suspicion is that this
barrel jack is connected to the five volts going out these guys and the five
volts going everywhere so let's try that I've got five volts set on my little
power supply here and you're running into a little barrel jack I've got a
current limited at an amp which is probably still too much but whatever and
confirm that there is five volts coming from there four point nine eight close
enough so here is the USB ports going out you center the hub the USB ports
right let's go across ground and five volts that's four point seven seven
volts that's a quarter of a volt drop to get there let's turn and then turn the
power supply now up to six volts they can't break this thing any worse than
already yes right so there's six volts even so if my theory is right this
should be about five and three-quarters of their votes yup
so this barrel jack is just coming in through one diode probably Schottky
diode if it's a quarter of a volt and then onto the bus so when we put
seventeen and a half volts on there we were throwing sixteen volts onto these
USB ports and to the chips no wonder she smoked so now
we know what happened let's see if we can find out what's blown in this mouse
it would be really nice if there was a low value resistor acting as a
sacrificial fuse or something my searching online tells me that there are
some screws underneath of this little adhesive plate here and maybe underneath
there so get in with a less spudger now normally I wouldn't bother to try and
fix the mouse but this one's very front well thing as the gaming mice go it's on
the it's on the bargain in but it wasn't so that box or something I think so was
there try right
there we go hoping either thing back together again
oh there's a lot going on in here okay so that LED window comes up through it a
white pipe from that little LED down there so that would be a triple color
LED got a little daughter board on the side here with I think some more LEDs on
it and then three little switches that is probably going out to the usb I'm
guessing the most real oh that's interesting so this little button on top
can either make that into a cookie mostly or just a free rolling one
interesting and there's another switch back here somewhere that there's
something okay and then switches there they're there they're all on the
unbranded presumably legitimate arm run as opposed to what a part of my mail big
cheap Chinese crud that's interesting but another switch back there Wow so
that's one of the things that makes us a gaming mouse other than the the RGB
goofiness is that it's got a whole bunch of extra buttons and all tunable things
like that is this hmm that's a magnet those are a pocket down here that's
magnetic already this one came with some extra weights so you can actually put
weight in it to do things so let's go so this goes down this sort of ribbon cable
goes down to the sensor on the bottom that goes out there that goes in there
okay and then this guy here is
of the brains and if it got way too much voltage it's gonna be smacked and it's
no doubt a purpose-built chip I don't know do you think that paper
label actually means anything RC g CB d r1 g 6b - hmm - the google no i didn't
really expect that to come up with anything so i have to look at what's
actually on the chip itself uh stm32 oh wow it's a micro controller that's the
I'm a 32 l/100 right then the stm32 l 100 r8 micro controller a 32-bit MCU ARM
Cortex yeah so a lot of brains going on inside this mouse and it's not just to
blink the lights either you can actually record macros and store them on the
mouse itself and program them on to one of those extra buttons which is why
these things are popular with gamers I guess however there we go up to three
point six volt power play so unless there is some kind of a no there's gotta
be some kind of a regulator or some kind of a power supply on this Mouse because
there's five volts supposed to be coming in from the from the USB right hmm we
need still be able to salvage this thing well depending on how that power supply
well if we found the power supply first of all and depending on how it died and
what it is this is actually a fairly well made little mouse there's a lot
going on in there I wasn't expecting that SD microcontroller
I guess some of that explains why they're getting 75 bucks for these
things at retail oh come on get over there there it is okay so know that has
that everything holding the board in yes it is oh-ho-ho-ho-ho that doesn't look
like a happy little device I'm going to guess that that's a voltage regulator
MBL Hz find a datasheet for that so I did some searching for that little fight
Punjabi and I could not find a datasheet or even referenced that part number
however its failure mode basically has all pins shorted together here's the
input 5 volts and all 5 pins are shorted to that which means when it died rather
than acting like a fuse it jammed that full 17 volts into everything else
including the microcontroller which means there's no going back with this
thing I suppose if I could find what the hell this thing is and I'm assuming it's
a 3 volt regulator but it is a 5 pin job' and who knows exactly what it is
I'm guessing a Louisville a little dropout 3.3 volt regulator regardless it
smacked this chip then we could get that STM chip or that SD microcontrollers
chip but we can't get the programming so we're toast it's just a waste of effort
to go any deeper into this thing but I guess that was an interesting
exploration now then I suppose since I am the one who brought this thing or
more importantly this thing into the house and gave it to my kid I guess I do
owe him a new mouse oh well live and learn
thanks for watching everybody I will talk to you later
hopefully with something a little bit more more happy than always dead
electronics that I can't fix