curiosity teardown: cable modem (with VoIP)

curiosity teardown: cable modem (with VoIP)

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starting off tonight with infinite reflection  baltic porter from sookrum's brewing in winnipeg   they described it as having roasty coffee  aromatics alongside robust malt flavors   and heats of dark fruit so i wasn't planning on  doing another teardown so soon after the last one   but i was up walking around and this tear down  pretty much literally dropped in my lap so here we go one muddy skanky old oh god what a mess  um cable modem i probably should have cleaned that   up before i did this but you know we're here  now so let's go with it this is an ares model   tm-602 g cable modem on the back we can see  that it has an f-type cable tv connector   a ac power input there's a reset button  there it's a usb connection there   is a ethernet connection it's labeled 10 100 so  obviously not the most modern pieces of equipment   and it has two rj11 telephone jacks on it this  particular box is used by our local cable company   just as a digital telephone terminal nothing  else it can do more but that's all they use it   for i guess because it is older equipment here's  the manufacturer's data sheet they oh hey with   integrated battery backup hmm i may have to  extract that if it and see if it's any good   so this thing is capable basically over the  cable tv plant of providing two voice over ip   lines that plug into normal telephone jacks so  you can use your old landline phone or reuse it   plus high speed data access again high  speed being up to 100 megabit per second   it runs on the docsis 2 cable standard high  speed internet as we said by a 10 or 100   oh okay or ethernet over usb 1.1 that's what  it does interesting so they keep going on about   this battery option includes the first and only  two cell lithium ion solution for up to eight   hours of standby okay based on the language  of that and the fact that it's only got a 10   100 ethernet connection i'm going to  guess this is quite old technology there's the specs if you're interested you  can pause this at some point if you want oh yes it is old technology 2008 wow not  much else to learn here let's just tear   the thing apart obviously i'm not going to  use it for anything and boy is my workbench   going to need cleaning up after this so on  this side we have the battery compartment   that came out easily enough that looks like ah   now it looks like it's a strap to yank the battery  out but obviously it doesn't want to come out if you thought that last teardown was  violent you ain't seen nothing yet so there's the battery pack it claims to be 8.4  volts 400 milliamp hours charges at 115 milliamps   or 33 watt hours okay what are the odds  that a 2008 vintage battery is going to have   any jam left in it at all i think we'll  set that aside for later exploration and see what's in here underneath all that of  course now the question is how to get into it the obvious choice is to look underneath there  for screws yep the feet always hide the screws   looks like there's four of them here will that fit that'll do okay but i doubt it there is that that is just the case  and does it just lift right out oh wow that's nice   okay uh there's some light pipes for the leds  on the front panel ah we've got the connector   for the battery that might come in handy if  the battery is any good at all let me just uh right that's a lot less muddy and messy   first thing we have over here is a very obvious  power supply section there is the ac coming in   we have an mov we have a thermistor we have a fuse  a capacitor across it then we have a couple of uh   chokes in series with that that's all just going  to clean up the power both coming in and whatever   ugliness this thing creates going back out again  then we have our good old friend the full bridge   rectifier no i'm not going to say it like he  does followed by a big smoothing capacitor   and then over here we have a chip and a transistor  couldn't find any information about that one   online but i'm going to guess it's a  switchboard power supply chip and we   have a transformer bridging over the generous  slots there look at that that is some isolation   we have also bridging across the gap to opto  isolators which will be providing feedback into   this guy and we have a little capacitor in there  i think it's class y is it class x1 y1 capacitor   so that looks like a very solidly designed  power supply good isolation good filtering on it   exactly what you'd expect to see so after the  transformer as you'd expect we have a dual diode   we have some filtering capacitors we have a couple  of transistors and a couple of diode packages in   slot 23 format that will be creating the reference  for and driving the led side of those two guys   uh what else do we have in here a couple of  inductors down in there i'm assuming those   are just filtering to go with these this guy is  marked you and i can't read its designation but   since it's got you know capacitor and  a larger inductor it's probably either   a boost or a box circuit going on in  there so over here we have what are you   lm324 which is a dual op amp package so  i'm going to guess that that has to do with   measuring the the charging circuit possibly  uses comparator for the for the battery voltages   on the charging possibly looking at battery  balancing because there's so many pins over there   another diode package several of those heavy diode  packages okay so that will all be dealing with   the battery charging and there is a battery  indicator battery status indicator and just   to the left of that whole setup we have a  little what looks like a programming header   not a lot of labeling on the back of it a few zero  ohm resistors around it for some reason there's   very little going on in the back there's a few  passives a couple of diodes and stuff like that   um that one little transistor but then we have  this package up in the corner here let's see   what he is zylolog zbf082ah blah blah blah ah  a date code as 42nd week of 2009. that goes   along with the 2008 that was in the manual  so that dates this thing pretty precisely   that zylog chip is an 8-bit  microcontroller with extended peripherals   oh it's got all kinds of stuff going on inside it  gpio internal oscillator 10-bit analog to digital   and all comparators temperature sensors uart all  the things you would expect from a microcontroller   anyway let's get back to what we were  looking at before we got distracted there   so i got all these little surface mount leds up  front that went through some light pipes that   i already threw in the garbage because they were  disgusting uh what is this little chip down here m28313cs can't find the exact match for  him but most of the things with the same   root look like 128k eprom so i'm  gonna say that's probably what it is   though if it's an eprom it's a little bit far away  from the processing going on where's that other   microcontroller it's way over there so yeah i'm  guessing that it probably belongs to one of these   big guys in here so now over on the left hand side  those transformers the big diodes and capacitors   those lead me to believe that we are talking to  the two phone lines two rj45 jacks or rj11 jacks   sorry and normally you would just expect these  to be two parallel ones but no they're not if   you look they're two separate circuits going  back here and everything's mirrored so and in   the data sheet we saw for the device that it can  have two different voice over ip uh lines on it   so that's what's going on in there some line  driving down there everything else isolation   from the line although i would have expected those  transformers to be way over here but yeah whatever   it's even got a pair of 330 ohm resistors you know  one for each line of each circuit just to match   the 600 ohm nominal impedance of a dial-up phone  line cool i'm guessing that this dude is in charge   of the telephony stuff let me go see if i can find  that data sheet dual channel wideband tracking   battery voice port device battery because on a  telephone line on a standard uh dial-up telephone   line there is voltage on the pair with the audio  and in telephony terms it's called battery voltage   this chip is designed for exactly this  purpose i don't see any beet soup in here   they were just really reaching for that acronym  so now then we get down into these three big   chips in here this ti chip again i couldn't find  a lot of information on it but i'm going to guess   that it is dealing with the ethernet stuff um  just because there's the ethernet and the usb   network connection which both have lines going  back to it so that makes a certain amount of sense   then these two with custom firmware on them  let me just peel those two stickers off and   see if we can see what the chip is underneath  them although i'm not holding out a lot of hope   that this is going to tell us much hynux  hy5du561622 ftp okay and this guy here when   i cleaned the goop off it i think i scrubbed  part of the part number off i'm gonna look a   little bit closer and see what i can find on that  but i'm not holding out a lot of hope we'll see   well that wasn't so hard to find after all it's  just 256 megs of ddr sd ram and that other one   after staring at it for a while under various  bits of magnification is a 32 meg flash memory   okay sure so those two will be serving that big ti  chip in the middle all right so that makes sense   that is ram and a flash memory servicing this  big ti chip that i can't find out anything about   which is obviously going to be a processor with  ethernet and usb natively on it there is a crystal   that is no doubt clocking it you can actually  see some traces going from it through the loading   capacitors into it so that makes sense also it's  got some programming headers down there which also   makes sense to have close to that show that is  most of the mysteries at least as far as i can get   except for what's underneath  this rf shielding can here nice it's not soldered down now first thing  in after the connector we have a bunch of   inductors bunch of capacitors this big honking  inductor and more little surface mount adductors   so that is just rf filtering with two different  sections over here one will be transmit one   will be received onto the cable at different  frequencies because the uplink and downlink   on a cable tv plant is significantly different  frequencies uh we have a chip in there looks like   ti logo on it and a crystal in here we  have a that's probably a transformer   and a handful of passives okay and what else  is going on down in there can we see any closer   you know what i got this thing from being good  to use i might as well use it okay that's better   so there you can get a little bit closer look  at the input section the rf input section to the   outside world with all of its inductors and stuff  and i stand by my original suggestion that that   is the combining filtering of both the receive and  transmit section going out that connector there so   now we'll slide over closer to this little chip in  its environment what does that crystal say 16 mig   it's reasonable for a clock am i two zero is that  a five six maybe a e hm i don't recognize that   logo initially i thought it was ti from a distance  but when you get up close that ain't it well there   we go that wasn't so hard to find after all it is  a single chip broadband tuner which i guess makes   sense can tune anywhere from 48 megahertz  up to one gigahertz 3.3 volt power supply

no tunable parts required it does everything  inside cool it also has some gpio so that   it can be controlled which makes sense  operates with a 16 mig crystal yes it does   applications in voip telephony modems cable modems  and packet cable wow that's exactly what it's   being used for we'll zoom back out again see what  else is in there fl 20 that is going to just be   an rf filter but other than that it's just a whole  bunch of capacitors and resistors on that side   let's go over to this other side here the other  side of the splitter essentially so that first   side so this side will be receiving the incoming  signal which means that this side will be probably   doing the transmitting i'm guessing  signals coming from there i'm not sure   i don't see anything generating rf in there   couple of what looks like diode packages in sot  23 type packages and then that guy is going to be   a transformer this guy here what else is  going on in there not too much in that side   hmm for an rf uh enclosure i was expecting a lot  more weirdness but that's fairly standard kind of   stuff in there okay so i think that is about  all the intelligence we can gain out of this   board without you know going crazy on it the last  thing i want to do is crack open this battery here   hopefully we'll blow myself up and uh see  what's inside it and see if they can be   salvaged just peel that bit off and this is  going to be heat sealed together which means   more violence and abuse as we've learned  from our scottish friend using the right   tool for the job is exactly what you need and  you're gonna get violent with these things aha that sounds successful   this sticker out of the way oh no i  avoided the warranty whatever will i do oh look it's 18 650s what a novel technology  you know they were talking about how it was a   new technology at the time now let's  see if we can get those out of there   let's see okay that's what it is it's uh 2s2p two in series two in parallel  there's one end there's the other end and there's some balanced charging leads okay i  don't expect to find any voltage on there oh hey   2.1 volts on that guy 2.0 volts on that  guy 2.0 volts in that guy and this would   be 2.1 because series parallel hmm those  might actually be rescuable after all   oh a protection circuit that may have saved us oh  and all i'm impressed with the build quality of   this product the design nice fuse on the battery  module that's a very nice touch i'm guessing   that is the charge control and that will be two  mosfets that disconnect it probably i like it   i'm not going to use it but i like it now i  will disconnect these into individual cells and throw them into my battery  conditioner charger unit here and uh   see what happens with them well that was  another successful and entertaining teardown   and i might even get lucky and get some uh some  cells out of it that i can use this thing didn't   immediately say abort mission when i plugged  it in so maybe they're still good we'll see   it's going to take some time i'm charging them  slowly so this crusty rusty old board i don't   know that there's anything of any value for me to  salvage off it the connectors are all corroded um   maybe you know the bridge rectifier  some of those capacitors maybe the   mov but other than that there's not a  lot of salvage value in this thing maybe   the telephone isolation transformers because  those are going to be just a one to one 600 ohm   transformer so that could come in handy maybe for  audio isolation kind of purposes other than that   so there's not that much of value on there other  than entertainment value oh thanks again for   watching i appreciate that always um any questions  or comments down in the comment section as usual   i'll put the results of these uh these lithium ion  cells uh down in the description after i finished   messing with them i'm going to run them through a  charge discharge cycle a couple of times and just   see what they can do um yeah that's everything  for tonight thanks for watching talk to you later

2022-05-11 01:42

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