Electronics Repair School

why was AC wall adapter used for older routers

Started by harp, Jun 03, 2023, 11:42 AM

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I'm wondering if there is a specific reason why some older routers used AC power (regular transformer) instead of DC?
Zyxel Prestige 600 series
Comtrend CT-5621T...


I don't know those routers but maybe they have an internal power supply (ACDC converter)? Do you have one? Have you seen the insides?


Ofcorse they have DC inside, near the input have rectifier and so on. But, why is forced to AC get inside? Pictures is from internet, for example. I see lot of this design, thats whay I question ::)


Quote from: harp on Jun 03, 2023, 03:37 PMBut, why is forced to AC get inside?

Ok, maybe I didn't understand the question. Don't know what you mean by force to get inside.


"Forced" I mean = "designed", it is logicaly - if AC is not needed then should put DC directly on pcb...
Ok, I ask on different way... is in router some components which funcionality depends on AC voltage?

Stagger Lee

Maybe because switched-mode power supplies become fully developed only after this time. I do not know exactly.


Hello All,
I believe the idea behind this design was the following :they could work from both AC or DC power adapters.


As Markello said, it's probably so that it can be powered by ac or dc.

If it goes directly to diodes then, if you are needing to give it power, then you can give it ac or dc, and it will still work. Technically the ac peak voltage is higher than the median voltage, so for example 12 volts AC peaks at 17 volts. And if you were powering such a device, you could probably power it with anywhere from 12 to 17 volts DC.


 The didn't want a wall wart that didn't fit in the power strip ?