Respected members,
My ADSL+ modem is rated at 10V 550 mA input, but the power adopter I am trying to replace with, is rated at 10V 750 mA output, as result the unit is overheating. It is working fine as I am surfing now, but the overheating will reduce its life, I reckon.
Please help me with, dumping the extra 200 mA in some sort of electronic component.
I don't want to temper with the the components inside the adopter, but fix something with the output already being received.
Thanks
Hi there,
As you probably already noted, not all wall warts are created equal. A wall wart rated at 10v 500ma from manufacturer ABC may not be the same as a wall wart rated 10v 500ma from manufacturer XYZ. The reason is sometimes the manufacturer makes a custom order from a company that makes wall warts, and they fully test their products with the wall wart they ordered. So if company ABC makes a wall wart and tests it with their product and it works fine they eventually ship. But if someone substitutes the wall wart made by company XYZ it may either under power it or over power it even though it has the same 'ratings'. Note that i quoted 'ratings' to bring to attention the fact that all ratings are not the same either.
With all this said, it's best to get the exact same wall wart from the company who specified it.
In your case where you want to use another wall wart that has a higher ampere rating yes your unit could be overheating most likely because that new wall wart can supply power at a higher voltage than the old wall wart, and that means more heat.
One thing you can do rather than parallel a resistor is to put a resistor in series, which would help to drop some of the extra voltage during use. Alternately, a diode or two in series to drop some of the voltage. You might have to experiment a little as to what value resistor or how many diodes you need.
For example, a 1 ohm 1/2 watt resistor would drop 0.5 volts, while a 2 ohms 1 watt resistor would drop 1v. A single diode will drop about 0.7v, and two diodes about 1.4v, and three diodes about 2.1v. If you try diodes, the type 1N4004 would work fine.
To test, you'd have to make sure the wall wart works ok during times of low mains line voltage unless you dont get that condition too much in your area, and then you just have to test it with the lowest line voltage you commonly see in your area. If you loose connection now and then you would have to lower the resistance or remove one diode and test again. Not hard to do but does require a little experimenting.