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AC/DC Adapter Charger Cord
The charger cord for my AT&T's DSL modem (2Wire 2701HG-B) died, so I
purchased a new one online at Amazon.com. The only difference between the original cord and the new one is that the old one output was 5.1V @ 2.2A, whereas the new one is 5V @ 2A. The modem seems to work ok with the new cord. But, because I am not a techie, I don't know if such a difference in V and A could damage my DSL modem in the long run. What do the experts have to say? -- tb |
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AC/DC Adapter Charger Cord
On 7/16/2017 6:22 PM, tb wrote:
2Wire 2701HG-B If it working and not displaying any intermittent problems then it is likely to continue doing so. The 0.1V difference is within the normal tolerances for such supplies and it is unlikely that the modem is drawing enough current that it is getting into the range between 2.0A and 2.2A. The ratings on the power supply (or cord as you call it) represent the absolute maximum output it can be expected to support continuously -- most devices connected to it will use considerably less. |
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AC/DC Adapter Charger Cord
tb wrote:
The charger cord for my AT&T's DSL modem (2Wire 2701HG-B) died, so I purchased a new one online at Amazon.com. The only difference between the original cord and the new one is that the old one output was 5.1V @ 2.2A, whereas the new one is 5V @ 2A. The modem seems to work ok with the new cord. But, because I am not a techie, I don't know if such a difference in V and A could damage my DSL modem in the long run. What do the experts have to say? According to this, one person here found a load of 1.2A. And that value is less than the 2.2A or 2.0A maximums allowed on your two powering solutions. http://www.dslreports.com/forum/r228...Supply-Problem The IC tolerance should be at least 5%. If there really is something running off +5V in there, it should at least tolerate 5.25V on the high side, or 4.75V in the low side. They could be attempting to compensate for voltage drop in the cord under load, but that seems pretty goofy. There's not much to see inside. It does have a power converter in the lower left, but may also be using the input power in raw form, elsewhere in the unit. https://wikidevi.com/w/images/1/1d/2..._board_top.jpg I don't see a reason to panic at this point. The 5.1V is clever, but also non-standard, and it's surprising anyone in China is sourcing an adapter actually set to 5.1V. But the objective is, to compensate for the ohmic drop. 5.1V minus (1.2A times 0.008 ohms) gives 5.0V at the plug. That's the idea. The cable has resistance, and the regulation point is inside the adapter. The adapter doesn't know what the voltage is at the plug, and maintains the voltage at a reference point inside the adapter. It doesn't use remote sense, like the 3.3V rail on an ATX supply does. (If you check your ATX supply main power cable inside the PC, one of the pins has two wires leading to the same pin, and that's the remote sense on the 3.3V rail only.) Wall adapters, and a lot of power sources, don't bother with remote sense as a feature. Boosting the output voltage like that, is a poor mans way to "fix" the drop in the cable. Paul |
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