Unlocking BT 2Wire 2700HGV Business Hub (wireless router)


Contents > Troubleshooting:




Repeatedly rebooting and Red Power Light (PSU fault)


Leif wrote to say he had been using a single SSID 2700HGV for over 3 years without problems.  Then recently, the hub went into a loop where it was repeatedly rebooting itself, then eventually the power light was just a continuous Red all the time.

He checked the open circuit voltage from the mains power supply and it was outputting 5.1 volts, so he concluded the hub was probably faulty.

He acquired a replacement brand new 2700HGV only to discover that behaved in exactly the same manner as described above when using the original 3+ year old power supply.   The new power supply worked fine with both hubs.

The original power supply unit (rated at 5.1volts DC @ 3 Amps)  was clearly faulty under 'load' conditions.


Comments posted on IDnetters forum suggest there may be a growing trend in failing UK power supply units coming to light with older hubs.

Apparently, www.digidave.co.uk offer replacement 5 volts compatible PSUs for UK use for around £10 including UK delivery but these appear to be rated at 2 Amps.  Acquiring a cheap 2700HGV from eBay may be more cost effective method of sourcing a replacement genuine PSU – ensure that any 2wire power adapter is supplied in its original sealed polythene bag, otherwise an used example, with 07 or 08 date stamp, may have a very short life.

Note that the BT 2701HGV-C uses a 12 volts PSU and is fitted with a different size of barrel plug.

Power Adapter output specifications

BT 2700HGV

5.1v @ 3A DC

4mm/1.7*mm plug, centre positive polarity.

BT 2701HGV-C

12v @ 2A DC

5mm/2.1mm plug, centre positive polarity.

(* = Inner diameter to be confirmed)

(Added 24 Jul10):  Jayson advised his 2700HGV suffered the exact same symptoms as described above by Leif. 

(Added 10 Aug10):  A relative's 2700HGV on BT Business Broadband which was newly installed in late 2007 suffered from a red Power LED immediately when switched on recently.  BT sent a replacement mains power adapter which resolved the problem.

(Added 3 Sep11): I think I've been using the same PSU for over 4 years and mine finally died today unexpectedly. Very similar symptoms. In fact, when I went to investigate, the power light was blinking green for several minutes, as if it was booting up. When I disconnected and reconnected the cable, the power LED was now emitting a continuous red light. It was also accompanied by a feint buzzing from the hub. When I checked the open circuit voltage, it was 5.3v, exactly the same as a brand new PSU. A brand new PSU (from a circa 2007/8 boxed hub) resolved the problem. It appears the old PSU is faulty under 'load' when the hub is trying to draw lots of current as other owners have previously reported.

(Added Sep 2013): The replacement PSU installed 2 years ago died unexpectedly. It was a 2007 made PSU. Open circuit voltage of 5.28v. There were 3 slightly bulging 'Rifeking' 1000uF/16v capacitors. The capacitors have now been replaced by Rubycon capacitors and the power adapter is now working fine.

(Added Dec 2013): I've dismantled a 'working' 2wire power adapter which was manufactured in 2010 (The first 2 digits of the 4 digits stamped into the plastic case correspond to the year of manufacture). It was originally supplied by BT as a replacement. The adapter has been in use for over 3 years. I found the capacitors within it were not leaking unlike other 2007/8 power adapters I had previously examined. It would suggest 2wire starting shipping longer lasting power adapters from 2010 onwards.

(Added Mar 2014): I was given a faulty power adapter, originally manufactured in 2008. It had been working for just over 4 years before it failed earlier this year – dim flickering red power LED on the hub. Adapter measured 5.2v with no load. Opened up the adapter to find 3 slightly bulging 1000uF capacitors. My multimeter can only test up to 20uF, but I did find one of the three capacitors was bad and didn't register a reading at all. After fitting new capacitors, the power adapter is now working again.

(Added Oct 2014): A new power adapter which I installed last December failed this week – leaking capacitor fault. The 2wire adapter in question was supposedly brand new, manufactured in 2007, but as it was not supplied in a sealed polythene bag, I now think it may have been a used item. I've now installed a new 2wire adapter (made in 2007/8) which was supplied in a sealed bag – only time will tell how long this adapter will last.

The above symptoms are very likely to be caused by capacitors going bad. ie. Leaking/bulging. This is a common problem with switched mode power supplies.

It is possible to replace the faulty capacitors but this is beyond the scope of most readers.

(Added Sep 2013):

2wire PSU YouTube video 1

2wire PSU YouTube video 2

I found it impossible to pry the two halves of the UK 3 pin power adapter case apart using a flat bladed screwdriver. In frustration, I did find an easier solution....

Place the power adapter on its side on top of a work bench. Use a large flat headed wooden mallet and strike along the visible joint. Turn it over and repeat for the other side. The blow causes the sides of the plastic case to flex causing the glue holding the two halves of the plastic case to crack. The two halves of the case can then be separated.

I've taken two PSUs apart in this manner. One PSU of unknown history was working. The other new PSU died after 40 minutes of use. Although they look identical externally, they were different internally.

The working PSU was fitted with three 1,000uF/16V 105C capacitors (20mm tall, 8mm diameter). These are probably low ESM variety. All three capacitors were bulging at the top, and so it was not clear how much life was left in it.

The other dead 'new' PSU (made in late 2009) appeared to have two 1,000uF/16V capacitors and a third smaller capacitor. Unlike other power adapters, the open circuit voltage with no load was less than 1 volt. This clearly had a different fault.

Rubycon perhaps make some of the best capacitors but they can be expensive. Otherwise, Panasonic also make low ESM capacitors. I didn't have problems finding them on eBay.

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