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dellsweig
Extreme Aerobatics
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join:2003-12-10
Campbell Hall, NY
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1 recommendation

Undersized Power supplies from Linksys.

There has been an interesting discussion in the DD-WRT forums regarding the power supplies and the power ratings for various Linksys routers.

»www.dd-wrt.com/phpBB2/viewtopic.php?t=54242

Bottom line is the spec sheets for the chip sets in the devices call for considerably more power than the Linksys power supplies provide - typical Linky PS is 1.0A

Many folks have been complaining about throughput issues on the switch, radio noise (clipping, distortion, drop outs) and random reboots.

There are some graphic examples how a simple 12V 5a power supply cures many of these ills.

Being one that needs to see it to believe it - I bought 2 12V 5A power supplies and tried them on my wrt310N's. Ths unit I bought

»www.12vadapters.com/adapter/powe···-5a.html

Has the correct plug and polarity already setup for the linksys.

My results are documented in the thread but suffice it to say I have never seen signal results (stregnth, SNR, noise) numebrs this good and the IPERF and DD-WRT bandwidth graphs are clean with none of the choppiness I have seen before.

Check the thread out - you will most likely end up ordering some new power supplies


Thane_Bitter
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Interesting information! Have to tested your router to see how much more current it now draws (as the old one should have only supplied a steady 1 amp)?

Its lame that Linksys is selling a product that would perform well provided the end-user provides a better power source.

I Played around with different power supplies on a older WRT-54GS and didn't see much of a change in signal quality (did find out that model can run on 9 volts but with an increase in current however).


dellsweig
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1 edit
said by Thane_Bitter:

Interesting information! Have to tested your router to see how much more current it now draws (as the old one should have only supplied a steady 1 amp)?

Its lame that Linksys is selling a product that would perform well provided the end-user provides a better power source.

I Played around with different power supplies on a older WRT-54GS and didn't see much of a change in signal quality (did find out that model can run on 9 volts but with an increase in current however).
No - I did not measure the current draw - before or after...

I am simply comparing performance data, both external (IPERF, wifi signal monitor) and internal (dd-wrt graphs).

The before and after views are telling - and as you can see from the dd-wrt thread - others are seeing and quantifying the same

Most likely linky ships a lower grade PS as the default firmware does not push things too much. also less problems as less load on the hardware?


koitsu
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reply to dellsweig
Do people realise just how much power _FIVE_ amps is? I don't even have full-blown 2U rackmount servers with 6 disks that pull that much.

This sounds like utter nonsense. All one of these tools has to do is purchase a kill-a-watt unit (I have two), hook it up, and run it through tests over a 24-48 hour duration.
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.


dellsweig
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said by koitsu:

Do people realise just how much power _FIVE_ amps is? I don't even have full-blown 2U rackmount servers with 6 disks that pull that much.

This sounds like utter nonsense. All one of these tools has to do is purchase a kill-a-watt unit (I have two), hook it up, and run it through tests over a 24-48 hour duration.
Did you bother to read the thread I refered to??

Have you read the datasheets for the devices being discussed??

Do you undderstand that a devices will DRAW as much power as needed - if the PS only supplies 1 Amp and the chipset needs more - well - I assume you know all this already

Automate

join:2001-06-26
Atlanta, GA
reply to koitsu
The amps being talked about are on the 12VDC side not the 120AC side so they are almost 10 times more than what you measure with a kill-a-watt meter. My guess is that 5 amps is overkill but 1 amp is not quite enough.


dellsweig
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said by Automate:

The amps being talked about are on the 12VDC side not the 120AC side so they are almost 10 times more than what you measure with a kill-a-watt meter. My guess is that 5 amps is overkill but 1 amp is not quite enough.
Exactly


Thane_Bitter
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reply to koitsu
said by koitsu:

Do people realise just how much power _FIVE_ amps is?
Sure, around 30.242 × 10^18 electrons per second.
It seems high but the supply voltage needs to be considered, at most dellsqeigs router is likely pulling less then 2 amperes of power, or put differently a reasonable 24 watts at most. P(watts) = V(volts) x I(amperes)

If it was drawing 5 amps at 120 volts (which it is not even capable of), he would have a desk sized space heater (and fire)
said by dellsqeigs :

The before and after views are telling - and as you can see from the dd-wrt thread - others are seeing and quantifying the same.
Accton' products (a certain Spanish company resells with the end user agreeing to certain promissory obligations) tend to get very flakey at lower power. In their case it’s not the lack of power, it’s what happens if AC power is briefly interrupted to the adaptor. The DC voltage drops low enough to lock-up the processor, but not low (or long) enough to reset it. The router jams till it is reset.

Linksys is saving a few bucks by using what likely is a lower cost adaptor. As long as the hardware is good (Linksys’ stuff general is), and it will take a 3rd party firmware (Linksys’ versions are poor), I would be happy to spend a few bucks and upgrade the adaptor to really make the router work.


FUBARinSFO
Premium
join:2006-03-25
Oakland, CA
reply to dellsweig
Dellsweig:

Just had the same problem, but with a universal 12DC adapter I happened to have lying around. Turned out it was only 500ma, so had the sort of problems you've described. Not often this is the solution.

On the other hand, I went to Newegg.com to try to find a spare -- forget it. They said it was a tech support question on their products, which they don't provide. Unbelievable.

-- Roy Zider

Posting to newegg.com:
-----------------------
Item#:12V DC universal power supply

Message: Hi: Where do you have 1A - 2A 12V DC power supplies for routers, modems, etc? Can't find them. Thanks.

Answer from newegg.com:
-------------------------
Dear Customer,

Thank you for contacting Newegg

We apologize for any inconvenience this may have caused you. Unfortunately we do not provide compatibility advice on any of the items we sell. Additionally, we do not offer product recommendations nor offer technical support. Since we are strictly a reseller and we do not have technical department, we are not in the position to give such advice concerning the recommendations or compatibility.

You might be interested in using our Advanced Search


dellsweig
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said by FUBARinSFO:

Dellsweig:

Just had the same problem, but with a universal 12DC adapter I happened to have lying around. Turned out it was only 500ma, so had the sort of problems you've described. Not often this is the solution.

On the other hand, I went to Newegg.com to try to find a spare -- forget it. They said it was a tech support question on their products, which they don't provide. Unbelievable.

-- Roy Zider

Posting to newegg.com:
-----------------------
Item#:12V DC universal power supply

Message: Hi: Where do you have 1A - 2A 12V DC power supplies for routers, modems, etc? Can't find them. Thanks.

Answer from newegg.com:
-------------------------
Dear Customer,

Thank you for contacting Newegg

We apologize for any inconvenience this may have caused you. Unfortunately we do not provide compatibility advice on any of the items we sell. Additionally, we do not offer product recommendations nor offer technical support. Since we are strictly a reseller and we do not have technical department, we are not in the position to give such advice concerning the recommendations or compatibility.

You might be interested in using our Advanced Search
This is the unit I bought for my wrt310N's. It will work for most Linksys routers.

»www.12vadapters.com/adapter/powe···-5a.html


koitsu
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reply to Thane_Bitter
Thanks folks. An EE-savvy friend of mine reminded me of the calculation formulas used for wattage and so on; 12V @ 5A is a heck of a lot less power than 120V @ 5A.

Said friend and I both read the dd-wrt.com thread, and it seems the majority of the focus/reports are coming from people who are intentionally increasing their transmit power way beyond the default scope of the router. For example, the OP is transmitting at the equivalent of 1.2W (yes, 1.2 watts). That's pretty major compared to the default these units come with, pushing ~45-60mW.

Can someone please clarify if this is truly a problem for the WRT* customer base as a whole, or only those who want higher signal strengths?
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.


Bill_MI
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Reviews:
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1 edit
Like Koitsu implies, there is much more to it that 1 current rating.

These power bricks are notorious for hype and snake oil, as well as ripple and bad transient response. There's a zillion little measurements in the power supply industry that may or may not be sensitive by the design of the unit (router) itself.

But I don't doubt for an instant Linksys may be using something just "good enough" because of cost. I believe the claims, just not some of the reasons. What may be needed is a *good* 12V@1A power source - not simply more current rating.


dellsweig
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1 edit
said by Bill_MI:

Like Koitsu implies, there is much more to it that 1 current rating.

These power bricks are notorious for hype and snake oil, as well as ripple and bad transient response. There's a zillion little measurements in the power supply industry that may or may not be sensitive by the design of the unit (router) itself.

But I don't doubt for an instant Linksys may be using something just "good enough" because of cost. I believe the claims, just not some of the reasons. What may be needed is a *good* 12V@1A power source - not simply more current rating.
Bill

I did nopt test under stock linky firmware but as I remember, stock linksys sets 28Mw for the transmit power.

Just for grins - I looked at my signal (from my wrt310N) with the stock PS and my 5a PS and compared signal quality, stability and overall data throughput (IPERF) at the 28Mw setting.

With the 5a ps - I got close to 10% improvement in Snr, less noise as well as the same improvement in overall signal strength.

Under the stock PS - I would see IPERF graphs where my data transfer would drop significantly for a second - I assume retransmissions or signal loss. With the 5a PS - I no longer see this.

I know its hard to believe that Linksys would go cheap on the power supply - but I have seen it with my own eyes...


Bill_MI
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Hi Dellsweig, I'm not doubting such tests. What I'd like to know is that same improvement may be realized using a better 12V@1A supply, too.

Actually, I'd love to see that test watching voltage level at the router power connector with an oscilloscope. After all... 12V@1A is 12 watts!


dellsweig
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said by Bill_MI:

Hi Dellsweig, I'm not doubting such tests. What I'd like to know is that same improvement may be realized using a better 12V@1A supply, too.

Actually, I'd love to see that test watching voltage level at the router power connector with an oscilloscope. After all... 12V@1A is 12 watts!
Someone on the dd-wrt forums used an analogy to audio speakers - where not enough power causes audio distortion - or clipping. I wonder if we are seeing the same here with the radio carrier??

I dont own a oscilliscope so I cant do that kind of analysis but the analogy makes sense

Expand your moderator at work


Bill_MI
Bill In Michigan
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2 edits
reply to dellsweig

Re: Undersized Power supplies from Linksys.

That's not a bad analogy. I don't know what the current demand looks on these routers but under-powered power supplies will coincide current demand with voltage dips. 12V may dip to 9V if it's really bad. "Distortion" means it's not a solid 12VDC. That's what a scope would easily see.

There's also the possibility the 12V@5A supply you're using is supplying more like 13, 14, 15VDC when lightly loaded - but the performance benefit comes with it. I don't know the power distribution but most modern switching power handlers are pretty tolerant over a large voltage range (it may never blow something but I could never say that fact is assured).

Anyone got a DC meter and can get on that voltage may be telling.

EDIT: Dellsweig, is that power supply "heavy"? The picture tells me is is NOT a linear supply with a heavy transformer but a light one which is surely a switcher type. Most are these days. A properly designed switcher type will often have better regulation, too. What about the original?

IRON = heavy transformer = linear supply
Light = switcher = poor design can cause problems but usually better and surely "green".

thedragonmas

join:2007-12-28
Albany, GA
kudos:1
said by Bill_MI:

EDIT: Dellsweig, is that power supply "heavy"? The picture tells me is is NOT a linear supply with a heavy transformer but a light one which is surely a switcher type. Most are these days. A properly designed switcher type will often have better regulation, too. What about the original?

IRON = heavy transformer = linear supply
Light = switcher = poor design can cause problems but usually better and surely "green".
i can tell you the ac adapter that came with my wrt54gl weights practically nothing. if my volt meter didnt die on me a few months ago id be glad to give ya numbers.


peter_m
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Canada, QC
Has anyone tried it on a WRT54GL ?


dellsweig
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said by peter_m:

Has anyone tried it on a WRT54GL ?
Just tried my 12V 5A supply on my WRT54GL - G Ap.

Saw a 10% improvement of WLAN to WAN speeds - still not as fast as my WRT310N for the same test.

Saw increase in signal quality and strength - about 10%

During WLAN to LAN IPERF file test - I saw less drops in the graphs - more consistent transfer

I think I will order another one of these for my WRT54GL - nice to see the same type of improvement as I have been seeing with the WRT310N


peter_m
Premium
join:2005-07-13
Canada, QC

3 edits
Excellent and thank you Dellsweig.
Going from the stock 1 amp to 5 amps sounds a little extreme. Are you able to measure how many amps the WRT54GL is drawing under load?

It might make for a physically smaller and more economical PSU...

Peter


dellsweig
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said by peter_m:

Excellent and thank you Dellsweig.
Going from the stock 1 amp to 5 amps sounds a little extreme. Are you able to measure how many amps the WRT54GL is drawing under load?

It might make for a physically smaller and more economical PSU...

Peter
I am strictly making observations on performance - I would not attempt to give you the electrical details.

As for size - the power blocks linksys (and other vendors) supply are a real pain - they generally dont fit on a power strip. The PS I picked up uses a simple yankee cord to the strip. Also - there is no downside to having sufficient power available - thats not to say that a 2a supply would not be fine - this is just what I purchased.


dellsweig
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1 edit
reply to peter_m
said by peter_m:

Excellent and thank you Dellsweig.
Going from the stock 1 amp to 5 amps sounds a little extreme. Are you able to measure how many amps the WRT54GL is drawing under load?

It might make for a physically smaller and more economical PSU...

Peter
Yet another SUCCESS story by upgrading the powersupply

»www.dd-wrt.com/phpBB2/viewtopic.···start=75

This is such a no-brainer - I wonder why EVERYONE isnt running out and doing this??


dellsweig
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reply to peter_m
said by peter_m:

Excellent and thank you Dellsweig.
Going from the stock 1 amp to 5 amps sounds a little extreme. Are you able to measure how many amps the WRT54GL is drawing under load?

It might make for a physically smaller and more economical PSU...

Peter
Peter

On the dd-wrt forum - power supply thread

»www.dd-wrt.com/phpBB2/viewtopic.···start=75

There is a graph showing signal and noise at 2A and at 5A

This shows that even 2 amps is not enough

HTH


koitsu
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reply to dellsweig
said by dellsweig:

said by peter_m:

Excellent and thank you Dellsweig.
Going from the stock 1 amp to 5 amps sounds a little extreme. Are you able to measure how many amps the WRT54GL is drawing under load?

It might make for a physically smaller and more economical PSU...

Peter
Yet another SUCCESS story by upgrading the powersupply

»www.dd-wrt.com/phpBB2/viewtopic.···start=75

This is such a no-brainer - I wonder why EVERYONE isnt running out and doing this??
Because not a single person has taken the effort to bring any of this to light with Cisco/Linksys. Until that happens, most customers are going to take this with a grain of salt.

Someone will need to get in touch with the right folks (specifically engineers) at Cisco/Linksys to discuss it, and have something done about it. If there's no response, keep trying other methods of contact.
--
Making life hard for others since 1977.
I speak for myself and not my employer/affiliates of my employer.


peter_m
Premium
join:2005-07-13
Canada, QC

1 edit
said by koitsu:

said by dellsweig:

said by peter_m:

Excellent and thank you Dellsweig.
Going from the stock 1 amp to 5 amps sounds a little extreme. Are you able to measure how many amps the WRT54GL is drawing under load?

It might make for a physically smaller and more economical PSU...

Peter
Yet another SUCCESS story by upgrading the powersupply

»www.dd-wrt.com/phpBB2/viewtopic.···start=75

This is such a no-brainer - I wonder why EVERYONE isnt running out and doing this??
Because not a single person has taken the effort to bring any of this to light with Cisco/Linksys. Until that happens, most customers are going to take this with a grain of salt.

Someone will need to get in touch with the right folks (specifically engineers) at Cisco/Linksys to discuss it, and have something done about it. If there's no response, keep trying other methods of contact.
Koitsu,
call me pessimistic but I think it would be a waste of time. We are talking about a $59 off the shelf product. Good luck getting an engineer. I think we have more chances of one of them stumbling on this thread and reading it then one of us calling techsupport.

Just my opinion,
Peter


dellsweig
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2 edits
said by peter_m:

Koitsu,
call me pessimistic but I think it would be a waste of time. We are talking about a $59 off the shelf product. Good luck getting an engineer. I think we have more chances of one of them stumbling on this thread and reading it then one of us calling techsupport.

Just my opinion,
Peter
I am convinced Cisco KNOWS the PS is an issue.

I have RMA'd a few WRT54G's and one WRT310N over the years. During the phone process with the Indian script reader, one of the tests they have you do EVERYTIME is to ask if you have another power supply and to swap that in to see if it fixes the problem

In fact, the WRT310N I RMA'd went back with a 1A power supply and the new/recond one had a 2A with an RF choke in the power line.


peter_m
Premium
join:2005-07-13
Canada, QC

1 recommendation

We can only hope they do something about it then.

I have hard time wrapping my head around the 5amp/12v PSU. I see the graphs and believe your data to be genuine. Just that it's 60 watts we're talking about! 60 watts should not be required for a device that doesn't heat up that much...

What could be causing the problem? The regulator inside to the WRT not handling sudden spikes in the power consumption? Power capacitors being too small?

Has anyone considered a 15v 2amp PSU? The internal voltage regulator can probably handle it...

Peter


Bill_MI
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1 recommendation

Peter, we're thinking the same. It's far more complex than getting down to ampere rating on commodity cut-rate power supplies. But no one is getting a meter on the delivered voltage - I'd wager it's ending up greater than 12VDC.

Someone familiar with the radio module may be able to confirm if it runs directly off the incoming voltage and gets "happier" with more incoming voltage. Transmit power is very "bursty" in nature and I wouldn't doubt there's some "good enough" in the design for handling sharp demand.

Everything else is surely off regulated 3.3V which should never notice such incoming fluctuations - if it does it's really a bad design.


peter_m
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Canada, QC

1 edit

1 recommendation

said by Bill_MI:

Peter, we're thinking the same.
I'm glad someone understood me... I feel better now. Thanks