Linksys Router Power Adaptors

Discussion in 'Other Linksys Equipment' started by fred3, Jul 27, 2008.

  1. fred3

    fred3 Network Guru Member

    I have quite a few WRT54G (x) boxes and quite a few RV042s as well.
    I just recently discovered that the power adaptors ("wall warts") are of two very different types:
    One is marked for output of 9VAC 1000ma
    Another is marked for output of 12VDC 500ma.

    Normally one must match with either DC or AC - they don't mix in general.

    I tested the adaptors with a simple voltmeter and got this:

    17.5VDC for the 12VDC model and 40VAC.
    10VAC for the 9VAC model and 0VDC.

    These results make reasonable sense in that a DC output model could still have a lot of ripple at the output - which would look like AC voltage to the simple meter. And, the higher reading of 17.5VDC could be caused by the ripple affecting the meter reading.

    And, 0VDC out of an AC to AC adaptor is exactly what one should get. The average of an AC voltage is zero.

    So, it appears that some Linksys boxes expect to be fed with DC. If so, there would be no "transformer" inside the box because transformers don't do DC - unless the circuitry is more complicated. But, why do that?

    And, it appears that some Linksys boxes expect to be fed with AC. If so, there would be some rectification inside because all the board electronics have to run off of DC of course. Then there could also be a transformer inside.

    If there's a transformer inside and simple circuitry for power then applying DC to one of these would likely get not much useful power unless the ripple is really high - which it appears it could be!

    If there's only a rectifier inside then either AC or DC might work fine.

    Anyway, I'm left with the quandary: which power adaptors go with which Linsys boxes? Is that information available anywhere?
  2. HennieM

    HennieM Network Guru Member

    All the WRTs I know of run off DC. 12VDC for the newer models, but (I think) the V1 WRTs ran off 5VDC.

    Some other (like Marconi) routers I have come across run off AC. No transformer in the router (as that would make the wall transformer obsolete), but rectification and smoothing.
    Reason for that IMO: The initial basic designs of the chip manufacturer included on-board rectification, so the OEMs just went with the exact design.

    You can run your AC fed routers off DC of course. I do that when people have spikey power - it provides smoothing in the DC wall supply, and smoothing inside the router.
  3. fred3

    fred3 Network Guru Member

    Linksys Power Adapters

    This was never about what the *boards* want. It's about what the stock power adapters deliver (and thus what the box wants just to make a distinction between the functional circuitry on the board and the power connector on the board). Then we don't have to get into things like transformers on the board, rectifiers, etc.

    I got some pretty good information from Linksys chat today. They don't publish this information so I suggested they just do that! In the mean time:

    In general you can find the power requirement near the bottom of the data sheet. The RV042 says 12V but doesn't specify AC or DC. It's DC.

    RV042 - 12VDC 1A

    WRT54GV8 12VDC 0.5A probably doesn't work on some of the others.

    BEFSR41 9VAC 1A <<<<<<< note well: this one says AC as do the power adapters and this is the one that I measured zero DC volts at the output - so I believe it's not a typo!!

    I do hope they publish the whole list.
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