Finally got sick of my DSL modem...

  • Thread starter Geeky1
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Geeky1

Geeky1

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My DSL modem has always been somewhat flaky. I suspect it's temperature related, as some of the chips in it hit as much as 70*C and are not heatsinked or cooled in any way other than just convection through small vents in the case.

I've tried to fix this problem once in the past by heatsinking some of the chips. I wrote an article about it for Short-Media (a site which I have subsequently left); the article is here:
http://www.short-media.com/review.php?r=244

That worked for about a year, but lately it's been getting flaky again. I'm pretty sure it's line-related this time, but when it went down last night, I took the opportunity to, ah, improve the cooling further.

Turns out that the heatsinks weren't doing a whole lot... I never measured it when I wrote the article, I simply assumed they'd help since I opened up the vents at the same time, and there was more area for the heat to radiate from. But I measured the temps again with my wireless thermometer last night, and i got about 73*C on the line driver (the heatsinked chip in the bottom right corner if the front of the modem is facing you) unheatsinked, and about 68*C with the heatsink. So it was helping, but not a lot.

With the fan, the temp. on that chip (which is easily the hottest-running chip in the device) dropped to 38*C. Not bad... Then I taped over the vent in the top of the case (there are also vents on the bottom and both sides) to make sure that any air the fan was getting was passing over the circuit board. That shaved another 1*C off the temperature of the line driver, bringing it down to 37*C.

I'd say a 31*c temperature drop is pretty impressive. :D

And I even installed the fan the *right* way... by drilling the PCB and adding a fan header and everything! :D





 
Lol! My modem has never got very hot at all. Well, it was some cheap one that came free with tiscali broadband. I personally think it's just a peice of hollow plastic with 2 wires held together with selotape. Still, use a wireless router now so it's just sitting somewhere getting dusty. Where a sagem belongs ...
 
Oh, the outside casing on mine doesn't get very hot either. But you have to remember that plastic is a very good insulator and air isn't that great of a thermal conductor. So if the outside of your modem's case is even lukewarm, it's almost a given that something inside is getting damn hot.
 
Geeky1
Oh, the outside casing on mine doesn't get very hot either. But you have to remember that plastic is a very good insulator and air isn't that great of a thermal conductor. So if the outside of your modem's case is even lukewarm, it's almost a given that something inside is getting damn hot.
Click to expand...

I would say that the bottom of mine is pretty hot.
 
if i could be bothered to open up my DSL modem i might do the same. it has been dropping the line a hellva lot recently, and im sure its baking the circuit as when i touch the modem its warm. its some cheap BT Voyager 105 modem thingymajig that came with aol (ughhh). actually, i could complain and get another free one sent out, and have 2 so i can get the current one modded but the family can use the internet while im working :D


edit: on the underside of the circuit, why is there a white microswitch????
 
Not terribly. It's audible, but it's not quite finished yet. I need to do two more things to it, both of which will reduce noise, should improve cooling a bit, and extend the life of the fan.

The power brick for the DSL modem is unregulated, so it's feeding the modem 13-15v instead of its rated 12. This causes the fan to spin faster than its rated speed, which increases airflow and noise, but at the expense of fan life.

So I need to pick up a 7812 +12v fixed voltage regulator to splice in line somewhere in between the fan and the power connector, which will reduce the noise and extend fan life, with not much impact on airflow.

The second thing I need to do is drill the bottom and front of the case. This will increase the intake area, which reduces the amount of vacuum the fan has to pull and significantly increases airflow through the case (axial fans do not pull vacuums) while significantly reducing noise.
 
Cool. Maybe watercooling it should be the next step? :P

I've always been surprised at the amount of heat build-up in devices of this kind. My mate's router used to overheat all the time, obviously taking the network down with it at the same time. I've got a US Robotics router myself, and it's a little warm on the underside of the case (which, as you say, translates to a bit of heat on the inside). I've not had any problems with it yet, though, so it should be OK.
 
I need to do this mod. My DSL modem gets very hot, and only after five to six minutes of operation. I have a fan on mine too, but it's a large room fan. I have to turn the modem up side down to get it to vent properly. Verizon said there's nothing wrong with it, despite it being so damn hot and making me shut it off every hour of so to find a new connection. I'm not sure if that is heat related, but I suppose it doesn't help.
 
Ah right! My modem has been very unreliable for months now, always assumed it was heat related, but i guess this really proves it. 👍
 

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