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Can power cord cause AC adapter to fail? *PICS*

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cb474
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Can power cord cause AC adapter to fail? *PICS*

#1 Post by cb474 » Fri Apr 10, 2015 8:50 pm

I bought a longer (6 ft) power cord for my 65W Lenovo adapter that I use with an X301 and extremely soon afterwards the adapter failed and I had to get another one.

This is the cord I bought (it says it's UL listed and RoHS compliant):

http://www.amazon.com/gp/product/B00QG1 ... ge_o01_s01

Literally the second time I used this cord with the adapter, I noticed weirdness (my ThinkPad wouldn't charge, then it worked after I unplugged and replugged the cord into the adapter). Then it was fine for a couple weeks. And then the adapter failed never to work again. Still, after that I checked the cord with a different adapter for a small flatscreen television and the cord seemed fine (the television powered on).

I really can't imagine how the cord could have caused this, but the timing was remarkably coincidental. Could the longer 6ft length be an issue somehow (the cord that came with the adapter was 3 ft)? Perhaps drawing current over a longer distance somehow stresses the adapter? I would assume if the cord was shorting out that this would just blow the circuit breaker in my home, not make the adapter fail.

It's the first time I've ever had an AC adapter of any sort fail.

So anyway, even though the cord seems fine, I hesistate to use it with my new 65 W Lenovo adapter. Any reason to worry? Or is it just a pure coincidence?

Admin edit: Added PICS warning.

axur-delmeria
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Re: Can power cord cause AC adapter to fail?

#2 Post by axur-delmeria » Sat Apr 11, 2015 2:51 am

Yes, a bad power cable can destroy an AC adapter.

Something similar happened to the 65w adapter of my dad's X220. It had problems charging, but the adapter was detected by Lenovo Power Manager. Eventually it died though.

The root cause is bad contact between the copper parts inside the C5 connector
Image
and the corresponding pins on the AC adapter's socket.

I discovered this when I reused the cord on a different AC adapter, one which had a LED power indicator.
When I plugged it in, the LED was blinking, which meant the output was fluctuating badly.
I immediately unplugged it, and inspected the C5 connector.

It looked OK at first glance, but I noticed that one of the copper contacts were a bit off. It's hard to explain purely in words, so here's a pic of a disassembled C5 connector:

Image

As you can see, the copper contacts look somewhat like a 3-petalled flower bud that's only slightly open.

The one I saw was just a bit more open, which meant that it doesn't grasp the pin tightly when it mates with the AC adapter's socket. I managed to close it a bit with a needlepoint tweezer.

Again, I'm not good at explaining purely in words, so here's a cross-section diagram of one of the C5 connector's holes:

Image

The black-shaded part is the plastic, the orange is the copper, and the green is one leg of the needlepoint tweezer.

Basically, I wedged one leg of the tweezer between the one of the copper "petals" and the plastic, slightly bent the copper inward, then did the same on the other petals. I did the same to the other holes just to make sure. :D

The repaired power cord is now used on an AC adapter for a recently rebuilt netbook.
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Re: Can power cord cause AC adapter to fail?

#3 Post by TTY » Sat Apr 11, 2015 3:21 am

I wouldn't use the 6 feet power cord for a ThinkPad AC adapter. The reasons:
1. The ThinkPad user's guide says: Only use power cords recommended by Lenovo.
2. Amazon specifies the power cord to be used with an Apple TV. There is no guarantee that Apple's connectors adhere to IEC 60320. Apple often do their own thing. If Apple's connectors don't adhere to IEC 60320, you have a problem.

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Re: Can power cord cause AC adapter to fail?

#4 Post by cb474 » Sun Apr 12, 2015 10:48 pm

Thanks for the replies. I appreciate all the detailed explanations. I understand what you're saying, axur-delmeria, about the loose connection--you did an amazingly clear job and the images are great.

TTY, I know that cord was specified for an Apple TV, but I chose it because it seemed higher quality than other options on Amazon. I assumed this type of cord is relatively generic. The only way it differed (in an obvious physical manner) from the original cord was that the plug that goes into the adapter was not quite as long, but it definitely went all the way into the female end on the adapter and seemed to make firm contact.

In any case, can anyone recommend a source of (6 ft) cords that would be more appropriate for the Lenovo adapters? Does this look better: http://www.sfcable.com/P-ZIP-06-EN.html? Or is this just a bad idea?

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Re: Can power cord cause AC adapter to fail?

#5 Post by TTY » Sat Apr 18, 2015 6:11 pm

cb474 wrote:Does this look better: http://www.sfcable.com/P-ZIP-06-EN.html?
At least it says IEC60320 C7. That's more than one could say about the power cord you have now. An Apple TV has a 6 W power supply. Your ThinkPad has a 65 W power supply. I'm not surprised that a connector, that was designed to deliver enough current for a 6 W power supply, not necessarily is capable of delivering enough current for a 65 W AC adapter. A C7 connector should be able to handle a maximum of 2.5 A, which is more than your 65 W AC adapter requires.

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Re: Can power cord cause AC adapter to fail?

#6 Post by cb474 » Sun Apr 19, 2015 1:09 am

Thanks for the thoughts.

Actually, the cord that comes with the 65W Lenovo adapter has printed on the plug that it's rated for 7A and 125V. The 6ft cord Apple TV card has printed on the plug that it's rated for 10A and 125V (even though the Amazon ad says 7A). And both cords are 18 gauge wire. So it seems like in that regard the "Apple TV" cord should have been fine.

It's also labeled as an E210037 cord, so I think it's a more generic cord than just for Apple TVs, even though that's how the one I got from Amazon was being sold. I see them being sold elsewhere not specifically for Apple TVs.

As I say above, the only obvious difference is that the plug itself that goes into the adapter is shorter than the Lenovo cable. But it definitely goes all the way in with extra depth to spare.

I'm still wonderiing if the failure was just a coincidence and not related to the cord. I may experiment with it again, since I found a replacement adapter right away for $5. Talking to people it sounds like AC adapter failures are not uncommon.

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Re: Can power cord cause AC adapter to fail?

#7 Post by brchan » Sun Apr 19, 2015 3:01 pm

cb474 wrote:I may experiment with it again, since I found a replacement adapter right away for $5. Talking to people it sounds like AC adapter failures are not uncommon.
Make sure it is a genuine lenovo power supply, or you might end up damaging your laptop. Unfortunately with generic power adapters, it ends up happening more often than not.
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Re: Can power cord cause AC adapter to fail?

#8 Post by cb474 » Sun Apr 19, 2015 10:40 pm

brchan wrote:
cb474 wrote:I may experiment with it again, since I found a replacement adapter right away for $5. Talking to people it sounds like AC adapter failures are not uncommon.
Make sure it is a genuine lenovo power supply, or you might end up damaging your laptop. Unfortunately with generic power adapters, it ends up happening more often than not.
Yeah, it's the exact same adapter I had that failed. Same P/N and FRU and all that. I found it used for cheap.

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Re: Can power cord cause AC adapter to fail?

#9 Post by TTY » Sun Apr 19, 2015 10:57 pm

cb474 wrote:The 6ft cord Apple TV card has printed on the plug that it's rated for 10A and 125V (even though the Amazon ad says 7A).
If that's printed on the plug that goes into the wall socket, it might be a rating for that plug only and not for the entire cable. There might be different numbers on the connector that looks like a C7 connector on the other end of the cable.

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Re: Can power cord cause AC adapter to fail?

#10 Post by precip9 » Sun Apr 19, 2015 11:04 pm

cb474 wrote:
So anyway, even though the cord seems fine, I hesistate to use it with my new 65 W Lenovo adapter. Any reason to worry? Or is it just a pure coincidence?
Answer: NO.
A 65 or 90 watt adapter at full load has a current input at the AC terminals of less than 1 amp. Even a very poorly constructed plug cannot heat up enough to damage the adapter. However, if contact is poor, the switcher circuit in the adapter may fail to start.

The likely cause of adapter failure is that it was a forgery. These are very common. Unless you purchase a "Lenovo" brand adapter from Lenovo, it almost certainly will be a forgery. And forgeries fail because they are very badly constructed.

If you want to purchase a quality adapter that is not branded as Lenovo, choose PWR+ or Anker.
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Re: Can power cord cause AC adapter to fail?

#11 Post by cb474 » Tue Apr 21, 2015 1:35 am

precip9 wrote:
cb474 wrote:
So anyway, even though the cord seems fine, I hesistate to use it with my new 65 W Lenovo adapter. Any reason to worry? Or is it just a pure coincidence?
Answer: NO.
A 65 or 90 watt adapter at full load has a current input at the AC terminals of less than 1 amp. Even a very poorly constructed plug cannot heat up enough to damage the adapter. However, if contact is poor, the switcher circuit in the adapter may fail to start.

The likely cause of adapter failure is that it was a forgery. These are very common. Unless you purchase a "Lenovo" brand adapter from Lenovo, it almost certainly will be a forgery. And forgeries fail because they are very badly constructed.

If you want to purchase a quality adapter that is not branded as Lenovo, choose PWR+ or Anker.
Thanks for the thoughts.

The adapter that failed was the one that came with my ThinkPad originally, so I don't think it was a forgery.

And the cable works fine when trying it with other ac adapters that take the same type of connector, so I think the contacts are fine.

Actually, talking to a couple friends with ThinkPads, they have both had adapters that were originally shipped with their laptops fail. It may be a coincidence that the couple of other people I know with ThinkPads had this experience, but it does not sound unheard of for original ThinkPad AC adapters to fail.

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Re: Can power cord cause AC adapter to fail?

#12 Post by cb474 » Tue Apr 21, 2015 1:37 am

TTY wrote:
cb474 wrote:The 6ft cord Apple TV card has printed on the plug that it's rated for 10A and 125V (even though the Amazon ad says 7A).
If that's printed on the plug that goes into the wall socket, it might be a rating for that plug only and not for the entire cable. There might be different numbers on the connector that looks like a C7 connector on the other end of the cable.
The 10A 125V numbers I referred to are printed on the C7 connector, not the plug that goes into the wall.

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Re: Can power cord cause AC adapter to fail? *PICS*

#13 Post by precip9 » Thu May 07, 2015 2:07 pm

A 90 watt adapter draws a maximum of 1 amp steady-state. Since it is a switching supply, there are current spikes of brief duration.

In typical laptop use, an adapter idles along at about 1/4 amp.

Traditionally, the test of whether a cord is adequate is determined by measuring the temperature of the plugs. You won't see any rise at all in your cord.

It is certainly true that loose contacts can cause an adapter to receive intermittent power. But even if the cord is perfectly tight and functional, powerline "junk" is a fact of life. An adapter has to deal with it, and legitimate ones do. But all of them are subject to breakage. Cost is a part of the construction, although these three brands stand out:
Lenovo (if genuine)
PWR+
Anker


The concern over power cord amperage may have origins in the "audiophool" community. Those people are attracted to large, important looking cords, because it influences the psychology of listening enjoyment.
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Re: Can power cord cause AC adapter to fail? *PICS*

#14 Post by cb474 » Thu May 07, 2015 5:18 pm

precip9 wrote:A 90 watt adapter draws a maximum of 1 amp steady-state. Since it is a switching supply, there are current spikes of brief duration.

In typical laptop use, an adapter idles along at about 1/4 amp.

Traditionally, the test of whether a cord is adequate is determined by measuring the temperature of the plugs. You won't see any rise at all in your cord.

It is certainly true that loose contacts can cause an adapter to receive intermittent power. But even if the cord is perfectly tight and functional, powerline "junk" is a fact of life. An adapter has to deal with it, and legitimate ones do. But all of them are subject to breakage. Cost is a part of the construction, although these three brands stand out:
Lenovo (if genuine)
PWR+
Anker


The concern over power cord amperage may have origins in the "audiophool" community. Those people are attracted to large, important looking cords, because it influences the psychology of listening enjoyment.
So your point is that my cord, even if faulty or the wrong design, could not have broken my power adapter?

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Re: Can power cord cause AC adapter to fail? *PICS*

#15 Post by precip9 » Thu May 07, 2015 9:29 pm

The forgeries fall apart at the lightest touch. They burst into flames. Any cause, from within or without, is possible.

With a genuine, or good third party adapter, the designs are very rugged. A power cord could not cause a failure. The current drawn by the adapter is so far below the design limit, 8 amps, that even if contact is bad, it will not heat up.

Every laptop adapter, since ancient days, is a "switching supply." This means that a pair of transistors is connected directly to the AC input. This pair chops the 60 Hz line into a high frequency signal, in the range of 40kHz - 100 kHz. Chopping is a violent "on-off" switching action that happens continuously. The interruption caused by a loose connector does not bother the very rugged components that comprise the switcher.

People habitually jerk the cord out of the socket. Plugs pull out by accident. HV pulses come down the line. A laptop supply handles all this well, except for HV pulses in excess of the design limit. Since laptop supplies are universal, accomodating 240VAC as well as 120, a pulse has to be pretty high. In 240V countries, notably Russia and India, surges can be so severe, supplies can be damaged. But not in 120V countries.
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Re: Can power cord cause AC adapter to fail? *PICS*

#16 Post by cb474 » Fri May 08, 2015 1:25 am

precip9 wrote:The forgeries fall apart at the lightest touch. They burst into flames. Any cause, from within or without, is possible.

With a genuine, or good third party adapter, the designs are very rugged. A power cord could not cause a failure. The current drawn by the adapter is so far below the design limit, 8 amps, that even if contact is bad, it will not heat up.
As noted in the OP, my adapter that failed was the original Lenovo adapter that came with my ThinkPad--but I had purchased a third party longer (6 ft) cord and the adapter failed right after I started using it.

Thanks for your detailed thoughts on the matter and explanation of the inner workings of adapters.

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Re: Can power cord cause AC adapter to fail? *PICS*

#17 Post by cb474 » Fri Sep 11, 2015 10:33 pm

Tybie Styan wrote:Yes your concept is looking right. Because the long wire for the less current causes problems many times. The reason for your damaged charger is clear that you used a long wire which caused the stress on your charger.
Thanks for the response.

I see many chargers for other laptops, though, that have very long power cables (from the charger to the wall), much longer than what comes with Lenovo chargers. They have similar amperage ratings. Why don't they have problems, if long cables with low current can really cause problems?

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Re: Can power cord cause AC adapter to fail? *PICS*

#18 Post by bill bolton » Fri Sep 18, 2015 7:16 pm

cb474 wrote:Or is it just a pure coincidence?
This :!:

Don't sweat on it.

Cheers,

Bill B.

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