Coda56 modem overheating after 8 months (janky fix).

[MartyS]

Got a Hitron Coda56 modem back in December so I could take advantage of higher upload speeds on Xfinity.

 

Been working great up until last night.  Status page shows all channels connected but no packets moving through the modem.  Pressing reset would get it to work for a little while, turning it off for a few minutes would get it to work for an hour, turning it off longer would get it to work for about 2 hours.  So, pretty obvious something was overheating.

 

Opened it up (warranty is only 6 months) and for thermal managment they used a steel plate and a 2 or 3 mm thick thermal pad.  Seems the thermal pad had gone bad.  Didn't have any pad material around so stuck an old CPU cooler on and it's been running for 4 hours.

 

Pretty janky setup I came up with using rubber squares to hold the old CPU cooler on so when I get some thermal pads I'll be putting the original plate back on.  Been so long I don't remember what CPU this cooler came from, probably a 386 or 486, maybe someone will recognize it:

 

[Levent]

I have had done a similar jank shit with my old X360 power brick using an intel stock cooler.

[OhioYJ]

Back when I was using cable, I thermal epoxied heatsinks on mine and installed a fan:

 

 

[jaslion]

Just keep it like this?

 

If its stuck on well like this is it's MAJOR upgrade compared to stock.

[monopoly_hater]

Alex would be proud.

[dogwitch]

my gpon box(not modem or router). get so hot. i have a fan on it. to keep it running at normal temps.

[OddOod]

4 hours ago, OhioYJ said:

Back when I was using cable, I thermal epoxied heatsinks on mine and installed a fan:

Nice! I just got a wall power to molex adapter and took an old case fan and some zipties to cool my old Arris SB8200

[MartyS]

6 hours ago, jaslion said:

Just keep it like this?

 

If its stuck on well like this is it's MAJOR upgrade compared to stock.

It is not stuck on very well, with time I'm afraid it would tip to one side and possibly short something out.  I guess I could do a little FreeCAD work and 3D print a more stable holder.  But I think I'll try replacing the pad first, it ran for a long time with a cheap pad that crumbled to bits when I removed it, I figure it should last a long time with a better one.

[MartyS]

My variety pack of thermal pads arrived.  There's a 1 to 1.5 mm gap between the stock plate and the chip, didn't feel like good compression with a 1.5 mm pad so went with 2 mm.

 

Been about 2 hours now and still working so hopefully it's fully back to normal now.  Actually should be better than original, better pad and the first thing I tried was opening up bigger holes in the case for better air flow.  Now there is a nice flow of warm air coming out of where I opened things up.

 

 

 

[MartyS]

Well, after about a week using the stock steel plate heat sink and the new thermal pad I started seeing error messages similar to when it started failing last time.

 

It didn't stop working but I didn't like seeing those messages, so I opened it up and the steel plate was almost too hot to touch.

 

I'm now back to the Pentium III cooler, been running perfectly with that for the last 2 weeks.

I added a 3rd screw into the edge of the plastic case to stabilize the heat sink.

[Alex Atkin UK]

On 8/24/2024 at 11:59 PM, MartyS said:

I'm now back to the Pentium III cooler, been running perfectly with that for the last 2 weeks.

I added a 3rd screw into the edge of the plastic case to stabilize the heat sink.

I was going to say, the Intel cooler was always likely to be the best option but its insane it came to that.

 

Its just bonkers to use a big metal plate when surely a smaller finned heatsink would actually perform better due to allowing more efficient convection, and leave better airflow over the RAM.  There's so much wasted cooling capacity with their design.

[MartyS]

8 hours ago, Alex Atkin UK said:

Its just bonkers to use a big metal plate when surely a smaller finned heatsink would actually perform better due to allowing more efficient convection, and leave better airflow over the RAM.  There's so much wasted cooling capacity with their design.

It's the cheapest modem on the Comcast approved list for mid-split (to get higher upload speeds).  By a lot, so I'm sure every part comes down to saving every little bit on materials.  The plate is obviously painted steel, a magnet sticks to it and when you scratch the paint the metal is the color of steel.  A plate with better heat conduction would probably be fine, but would cost a few bucks more.  I'm guessing the issue with mine is the board warped a little, increasing the gap between the chip and the heat sink.

[Alex Atkin UK]

1 hour ago, MartyS said:

It's the cheapest modem on the Comcast approved list for mid-split (to get higher upload speeds).  By a lot, so I'm sure every part comes down to saving every little bit on materials.  The plate is obviously painted steel, a magnet sticks to it and when you scratch the paint the metal is the color of steel.  A plate with better heat conduction would probably be fine, but would cost a few bucks more.  I'm guessing the issue with mine is the board warped a little, increasing the gap between the chip and the heat sink.

But then it wouldn't have warped if it was cooled efficiently to begin with.

[Donut417]

1 hour ago, MartyS said:

It's the cheapest modem on the Comcast approved list for mid-split (to get higher upload speeds).  By a lot, so I'm sure every part comes down to saving every little bit on materials.  The plate is obviously painted steel, a magnet sticks to it and when you scratch the paint the metal is the color of steel.  A plate with better heat conduction would probably be fine, but would cost a few bucks more.  I'm guessing the issue with mine is the board warped a little, increasing the gap between the chip and the heat sink.

So basically what you're saying is that modem is not that great so stay away from it. LOL. 

 

From what I have read, only Node + 0 areas can get mid split. So the rest of us poor bastards have to wait for Docsis 4. Those modems have not been released yet and Comcast hasn't been clear on what the plans are for deploying that across its network, besides a few select areas. 

[Alex Atkin UK]

3 minutes ago, Donut417 said:

So basically what you're saying is that modem is not that great so stay away from it. LOL. 

 

From what I have read, only Node + 0 areas can get mid split. So the rest of us poor bastards have to wait for Docsis 4. Those modems have not been released yet and Comcast hasn't been clear on what the plans are for deploying that across its network, besides a few select areas. 

It boggles my mind they are pressing ahead with DOCSIS 4.  Granted were tiny in comparison, but the cable company in the UK are ditching DOCSIS and going FTTP as its so much easier to upgrade in the future then.

[Donut417]

Just now, Alex Atkin UK said:

It boggles my mind they are pressing ahead with DOCSIS 4.  Granted were tiny in comparison, but the cable company in the UK are ditching DOCSIS and going FTTP as its so much easier to upgrade in the future then.

Comcast owns Sky over in the UK. Have you heard of them pushing Fiber? 

 

Also in some areas they do offer Fiber. It has to do with what strings are attached to government supplied money. But in existing areas it's all Docsis for the most part. Also this is the company that thinks data caps are necessary in 2024. 

[Alex Atkin UK]

9 minutes ago, Donut417 said:

Comcast owns Sky over in the UK. Have you heard of them pushing Fiber? 

 

Also in some areas they do offer Fiber. It has to do with what strings are attached to government supplied money. But in existing areas it's all Docsis for the most part. Also this is the company that thinks data caps are necessary in 2024. 

Good point.  Due to the government requirements for the main telco to share their infrastructure with ISPs, Sky over here use their DSL and  FTTP, plus recently signed to one of the alternative fibre networks too.

 

They've also been doing TV over broadband for many years now as an alternative to satellite.

 

The free-to-air broadcast network also seem to trying to move to over the Internet.  The intent I think is to eventually sell off all the spectrum to cell networks.  Seems pretty inefficient doing all that over unicast and potentially problematic for rural areas.

[MartyS]

2 hours ago, Donut417 said:

So basically what you're saying is that modem is not that great so stay away from it. LOL. 

 

From what I have read, only Node + 0 areas can get mid split. So the rest of us poor bastards have to wait for Docsis 4. Those modems have not been released yet and Comcast hasn't been clear on what the plans are for deploying that across its network, besides a few select areas. 

Since it's half the price of the others on the approved list I'd say it's worth the gamble if you have the skills to do some DIY fixes.  When cooled properly it does what a modem is supposed to do perfectly fine.

 

Comcast upgraded my neighborhood about 2 years ago, but they then pulled a bunch of nonsense with requiring customer owned modems to have some extra features to get approved for mid split (after almost a year of only rented modems getting the higher speeds).  So even though the DOCSIS 3.1 modem I was using before could technically do it there was no chance of it ever being updated for the higher upload speeds on the Comcast network.  If this modem dies completely I'll just go back to my old one and live without the extra upload speed, it's only useful on the rare occasions I upload a video to YouTube.

[WL1]

@MartyS Thank you for documenting your work on this modem.  There are many stories of this particular model doing well initially, and then failing frequently enough in odd and sporadic ways after several months of usage.

 

I'm wondering if you have any updates on your fix?  Is the modem still behaving as it should?

 

I'm debating between this one vs. the Arris S34 vs. Motorola SB8611 for an DOCSIS 3.1 / 2.32 Gbps upgrade.  Both of the other 2 models are 2x the cost.  If all it takes to keep it functional is strapping a case fan on the side of the unit that's not so bad.

[MartyS]

On 4/6/2025 at 7:53 PM, WL1 said:

I'm wondering if you have any updates on your fix?  Is the modem still behaving as it should?

 

It is still working perfectly fine with the Pentium III cooler on there.  Getting 930Mbps down, 175Mbps up on speed tests, my plan is 800/150 so all is working well.  Pretty much hitting the limit of my 1G Ethernet setup in the house on downloads, but real world downloads rarely go over 850 so I have no plans to upgrade my router/switches/PCs to 2.5G.

 

I guess if we get a really bad heat wave this summer that will be the next test, if it acts up again if the basement gets hot I could always stick a tiny fan on that cooler.