HP Pavilion DV7 AC Adapter Safety Considerations

Aug. 17, 2009 - PRLog -- It can not be stressed enough that all UPS's are potential death traps. The line voltage in any country is lethal. Any HP Pavilion DV7 AC Adapter voltage higher than around 50 V is considered hazardous. So you should know some laptop ac adapter safety guide, before you buy your Dell ac adapter.
UPS's using a single 12 V laptop battery can cause injury. The batteries used can supply large currents if short circuited. It is easy to lose a finger if a ring shorts the battery supply. The risk is that the ring becomes hot, causing cauterisation of the blood vessels. With no blood supply, the only solution is amputation.
The other risks of shorted batteries is the potential for the battery case to split open releasing Dell AC Adapter electrolyte, and flying molten metal. The HP Pavilion DV7 AC Adaptersupply of units in the 2 to 3 kVA range from 48 to 96 V. The 96 V units float the laptop battery bank at 110 V, which will electrocute.
On-line units work at high laptop ac adapter voltages. In Australia, the nominal line Dell voltage is 240 VAC which when rectified, results in power rails of plus and minus 350 VDC. That is a total of some 700 V.
When working on UPS's, the use of an earth leakage circuit breaker/residual current detector, or whatever they are known as in your part of the world, has to be considered mandatory.
Some manufacturers, for cost reasons, do not use line monitoring transformers. Instead, high value resistors are used to divide the line HP Pavilion DV7 AC Adapter voltage to a value suitable for the control electronics. This results in a machine that is technically totally live. Keep a watch out for these ones and test before touching.
Be aware that the ground clip of an oscilloscope probe is earth. Depending on wiring rules, earth may be bonded to neutral at the main switch/fuse panel. This is true in Australia. Use an oscilloscope with differential HP Pavilion DV7 AC Adapter inputs designed for the job. A suitable alternative is an add on differential input unit in conjunction with a standard scope. The design presented in Elektor Electronics around 1994 works very well and with a bandwidth of 15 MHz, nothing will be missed.

HP Pavilion DV7t AC Adapter Features/Specifications from http://www.usadapter.com/Laptop-HP-Adapter/HP-Pavilion-DV... :
Input: AC100-240V (worldwide use)
Output: DC18.5V 3.5A
Power: 65W
Connecter size:
Internal Diameter: 5.0mm
External Diameter: 7.4mm
With central smart-pin inside
Attention! Please make sure the part will match your laptop. If there is no central pin in the connector of your original AC adapter, please stop bidding this item.
Item Includes: AC Adapter and Power Cord.
HP Pavilion DV7 AC Adapter

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