Fixing the AC adapter for a 2Wire 2701HG DSL modem by replacing the failed capacitor

2Wire seems to have a problem with their DSL modems’ AC adapters failing, affecting models 1701, 2701 and similar models.  Here I describe a failed modem AC adapter and the steps I followed to repair it.  I include photographs of the AC adapter under repair and more information about cracking open the case and the capacitor required.

When a 2Wire 2701HG DSL modem AC adapter fails, the typical symptoms are 1) you can’t connect to the Internet with it, 2) the modem will not serve a connection to its administration page ( and 3) the power light is steady red or blinking and the wireless light is steady green.   Resetting the modem does not fix it.  The modem will not go through the normal power up sequence when plugged in as described in the install guide available here.

A quick Internet search will reveal that this is a common problem and typically caused by the AC power adapter failing. This is a good page describing the problem and solution at

The typical reason that the AC adapter fails is because a single capacitor inside the adapter has failed.  The failed capacitor is a 1000MFD 16V electrolytic capacitor.  Failing capacitors are not an uncommon problem for electronics as I have previously discussed “Bad Capacitors – LCD monitor repaired.”

This failure can be fixed by buying a new modem, buying a new AC adapter or replacing the failed capacitor.

To save time and money I replaced the capacitor.  You too can replace the capacitor with basic tools and soldering skills.

This saves money because ATT (or your DSL provider) will either recommend a new modem for $79 or if you request a new AC adapter, that will cost you $10 + tax with free 2 day shipping (overnight shipping is available for an additional $14.95) at the ATT website.  You can also find replacement AC adapters at eBay, Radio Shack or electronics stores for a similar price.

The AC adapter required has an output of 5.1VDC 2A and looks like the following picture.

2Wire AC adapter
2Wire AC adapter

I repaired the AC adapter by replacing the failed capacitor.

To open the adapter, I used a putty knife and small hammer to loosen the seam holding the 2 halves together then I tapped around the entire seam with a screwdriver handle like I was opening a stuck lid on a jar.  This was enough to separate the 2 halves.

inside the AC adapter
Inside the AC adapter.

I located the suspect capacitor – 1000MFD 16V and inspected it.  Sure enough the top was bulging, a sign of a failed capacitor.  The inside of the case also had a burnt electric smell.

Inside the AC adapter
Inside the AC adapter. Note the failed capacitor (green cylinder) has a bulging top.

I purchased a new capacitor for $1.19 + tax at my local friendly electronics store (Metro Electronics, Sacramento, California).  Update 2016 – sadly Metro Electronics closed, I will miss the friendly local store.

A few notes on the capacitor:  The required capacitor for this repair is a 1000MFD, 16V, 105 degree, electrolytic capacitor.  If you can’t find a 16v one, you may substitute a higher voltage like a 25v and it should still fit OK in the case.  Do not use a lower temperature rated capacitor.  Note that the capacitor has polarity, the negative lead is marked with a stripe on the side of the capacitor.  Observe the polarity when you replace it, in this case the negative lead goes in the circuit board hole further from the edge of the circuit board.  You can find a replacement at an electronics store, Radio Shack or online, for example

I replaced the capacitor and glued the case back together with some plastic cement and tested it with the modem.  It worked.

Good luck with your project!

10 Replies to “Fixing the AC adapter for a 2Wire 2701HG DSL modem by replacing the failed capacitor”

  1. Thanks a lot for providing us reader’s a useful information when in comes to fixing AC adapter for a 2 wire DSL model by means of replacing its failed capacity. As well as the pictures above gives a better understanding for the steps given. [ dsl modem guide (dot) com ]

  2. Thankyou.
    But My Modem Is powering up normally< later it blinks and all the LEDs become red.
    Is the Issue still with the capacitor? Then i have to restart frequently

  3. Thanks for the great tip about replacing the 1000MFD capacitor! My router broke down and I suspected the A/C adapter, so I replaced the capacitor and got it working again.

  4. My DSL modem stopped working last night and as is mentioned above the problem was with the 1000 uF capacitor. I simply replaced it with a new one and now it is working like a charm! It only took me about 5 minutes.
    Thank you for the useful tip.

  5. Thank you very much, it is working now. I learn something again. One more time thank you, Bernard.

  6. I am one hour post do-it-yourself repair of my Samsung LCD and I have to be hosnet with you. . . . It is very simple. I have never done any kind of electrical work but was intrigued by all the stories of people fixing it themselves. I replaced four capacitors at .98 each. . . . EACH! Had I owned a sodering iron this repair would have only cost me $4.00. I encourage you all to give it a try. . . you will surprise yourself! Good Luck!

  7. Have a Samsung lcd tv model LA46M81BDX. Same problems. TV steartd by not displaying DTV channels without turn off/turn on power. That worked for a few months. Then tv steartd to turn itself on at random day/night. Then finally the clicking relay and no power up. Removed the back cover which was quite easy and exposed power board. Found the two low voltage electrolytic caps (2200uF) had bulged. Cost less than $5 to fix. Average soldering skills needed. Was prepared to toss the tv out at one stage.

  8. Thanks for the fix!…..I replaced both the 470 MFD and 1000 MFD capacitors -both appeared to be leaking black ooze. All good now!

  9. I bought a couple of 16v 1000uF 105 c capacitators, but then I looked inside and there are quite a few capacitors inside. The blown up black ooze ones are near where the plug enters the casing, are smaller, purple, czl 105 c, and look less like what I bought than a few lower rater capacitors in another section of the power supply/ac adapter. One is very much smaller. Ill have to unsolder them to read any other numbers and ratings on them and mark or remember which is the negative polarity. LOOK INSIDE BEFORE YOU GO CAPACITOR SHOPPING. This is just for whats going to be my backup modem, but I really appreciate the info and this probably wont be my last ac adapter fix.

  10. Pam,
    Thanks for the note. Sorry you did not find a simple fix, ie the big capacitor failed.
    Good point to inspect for obvious leaking capacitors first.
    My record so far replacing capacitors – fixed 2 AC adapters, failed to fix 1 AC adapter. Fixed one LCD monitor, failed to fix one LCD monitor.
    Glad I could be of some help and happy to meet another person into fixing things.

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