Failed Linksys WRT54G router (newbie)

[cassetti]

Hey all

I just found this site - read part of the FAQ - all i can say is WOW - i never realized that a failed cap is such a big possible reason why computer related equipment could fail!

Here's the scoop - 2 or 3 years ago - i forget exactly how long ago - I was working for radioshack - and finally convinced my mom to buy a wireless router. I had heard such rave reviews about this new WRT54G router - and i have had linksys routers/nic's before - and never had problems with them. So we bought a wrt54G - this was one of the first versions - i think it even came with firmware release version like 1.05 or something.


Anyway - it worked great for years - one day my mom calls me (i moved out so now i can provide only phone tech support most of the time) - and says the internet is down. After several days of calls with her - i finally stop by and check it out - the router is the cause - no lights were on - i would unplug it - and plug it in - a light or two would flash and then go off. Nothing would happen besides that

My mom ended up going out and buying a replacement wrt54G - but i still had the dead one.

now, a few months later - i'm moving into a new and bigger house - and found the dead wrt54g - i pluged it in and now nothing happens. I decided to pull it appart - and see if i could see any dead components.

Nothing visible - so i pluged it in to see if i could use my multimeter to trace the voltage and see if it was getting juice.

First thing i heard - was a very low hissing/electrical-buzz noise. It was comming from somewhere near the inductor / 2 capacitors.

well both caps are the same size - 16 volt 1000uF

I am a college kid with very little circuit training (took a boolean logic class, and i build home theater systems for fun - including the crossovers, but thats about the extent of my knowledge on electrical circuits) - but using my multimeter - i discovered that the two capacitors had very differant voltage readings (unpluged the power supply of course)

I tested the resistance and amperage. Now obviously i should have used some better methods of testing - but i suspect that since the noise was comming from the two caps - and the board is pretty empty in that area of the noise except for the inductor and 2 caps. I'm pretty sure that its a cap.

I'm going to go to radioshack and pick up some replacements caps, and replace them - if it doesn't work - no worries. I read up on how to desolder and replace the caps - no worries on that end - i've done plenty of soldering in my time (like i said - i build various types of crossovers for my audio systems) - but i'm just concerned about what caps to get.

I don't care if they are low quality - since the firmware will be upgraded to a tibor (hyperwrt) os so i can use it as a wireless repeater to extend the coverage of my wifi for the house (i have 2 laptops and am building an HTPC that will have wireless access to my media server)

I thought i read somethign about using a higher voltage is ok for capacitors correct?

If i can't find 16volt 1000uF locally (no sense in buying some caps online to fix somethign worth $20 tops - and spending $5 in shipping) - what should i do - i have enough space to rig up caps in series/parallel to make it get 1000uF - but voltage is the biggest concern.

Thanks for the help!

[Per Hansson]

Re: Failed Linksys WRT54G router (newbie)

It comes with the wifi card in a MiniPCI slot right? if so it is the v1.0 revision... See: http://www.linksysinfo.org/modules.p...showpage&pid=6

You need to use LOW ESR caps rated for 105°C, else it will not work I'm afraid... And yes, you can use both higher voltage and capacitance, (within reasonable limits=50% or so) but never lower (unless you really know what you are doing)

But are you sure the power adapter is working fine? I.e. is it giving out the rated voltage?

[gonzo0815]

Re: Failed Linksys WRT54G router (newbie)

Well you don`t need ultra low esr caps on that device in all circumstances. The circuit is a simple switcher and probably can work with severall generall purpose caps without problem. So at least for testing you can use normal caps. On the input there are a voltage between 12 to 20v depending on the load of the wall plug. So i won`t go mutch lower than 16v.
At the output, e.g after the coils and rectifier diode there is IMHO only 3,3 and 5v, so you can use anything above 6,3v
More is always possible, but not better than slightly above the used voltage. For long time operation with normal caps i recomend to ad several not that high capacity caps over one large, due to decreased ESR with any cap in paralell.

But anyway, the problem with those devices is not always the caps. Sometimes the firmware is the problem, an indication for that is if on led is blinking very fast. than the only thing is an Jtag adapter for reprogramming or the pin 16 short trick to load the failsafe settings, allowing to flash a ne firmware.

[arneson]

Re: Failed Linksys WRT54G router (newbie)

Those almost always need the new firmware, and they run pretty warm, even more when modem sits on top.
The dead ones I have I assumed took a hit from power or network jolt, didn't think about those caps, hmm.

[boldie]

Re: Failed Linksys WRT54G router (newbie)

Hi, Was anyone of you able to repait the linksys. As of yesterday I'm having exactly the same problem as cassetti.

TIA

[gonzo0815]

Re: Failed Linksys WRT54G router (newbie)

First of all you should chek if it is indeed an cap problem. Try to reset the router acording to the manual. if that won`t work for you, try to use the tftp option in flashing a new firmware. google for it, you will find how it should be done.
If that will not bring back your router you can eitiher try the pin 16 short trick, wich could hamrm the router, but i have tried that severall times /after some badflashes of new firmware) and my router is still going strong.
But to sort it out, you can easily solder some caps in paralell with the current , if that will bring it back on duty, the case should be clear.

[cassetti]

Re: Failed Linksys WRT54G router (newbie)

Boldie - linksys was very helpful - they were offering to replace it for me - it had a 3 year warranty - but i needed to show them a receipt so they could verify the proof of purchase - and the date it was purchased. I didn't have it. I contacted radioshack - since i worked for them a while back and i knew they keep copies of receipts. However - they said that they needed a credit card - and i'm 99% sure that i purchased it using a $100 bill that my mom gave to me to buy it for the house.

So i was S.O.L. and decided to go this route.

I searhed for the tftp option but i couldn't figure it out.

The thing is - the thing will not power up no lights come on. The AC adapter is giving the proper voltage. But the thing is not powering up at all.

There are two caps as i stated before - right next to each other. I do not think they are run in series or parallel - the router is in my new place - and i'm still on the net at my old place (moving) - but if i recall - the traces on the board lead to different directions.

But none the less - the two identical caps are located right next to each other. If i replace one. Should i replace the other?

Where can i find the 16 pin short trick?

I did try resetting it - but that never worked. - no change in its symptoms.

I had a failed power supply on my computer (old one - its at least 7 years old) - there are a ton of caps in it - small and large - i know to be careful around the caps - but i'm going to do some searching around on the board and look to see what i can find.

[lfuller1]

Re: Failed Linksys WRT54G router (newbie)

I too have a failed v1 WRT54G router. Measured 5v at the power plug, but this simple switching power supply has failed.

I replaced the PS with a 5v 2.7amp unit that I found on the web at All Electronics, and it now works like a champ..

Try another 5v PS on the unit. Be careful as the newer WRT54G units use a 9v PS.

Larry

[gonzo0815]

Re: Failed Linksys WRT54G router (newbie)

Ups, all new Wrt at least from the 2.0 upwards are using 12v wall plugs. The input voltage of those simple switchers could be as high as 40v DC (but not for the installed caps!). So if your router is actually powerd on 5v, i am not shure, if there is any smps in there.
In any way, if absolut no light will be on or flashing, then ist seems to be an badcaps or bad psu problem.


So i googled for some pics of those other versions of this router and it seems to be very different smps configurations on every version.
At the v1.0 it seems to be some MC34063 configuration, so it could be bad caps and it is an smps circuit. As far as is know, the o/p voltage should be 3.3v.
So if there is no 3.3v, replace first the caps, if nothing happens replace the smps controler too. But first i would try to hock it up on a other wallplug or e.g to an ATX PSU of an PC.
It wouldn`t make mutch sense to solder on an unit where ionly the wallplug is bad. You should meassure the voltage under load.

[boldie]

Re: Failed Linksys WRT54G router (newbie)

I just did some measuring and the voltage is around 4.5 Volt, sow it seems the powerplug is doing what is should do but I still haven't got any led's on... Thus I will be looking for a replacement PS with 5V and 2.7 amp instead of the original 5V and 2.0 amp. But then again how can I be sure it will solve te problem....

[cassetti]

Re: Failed Linksys WRT54G router (newbie)

Here's what i'm going ot do - i'm putting my version 1.0 together (found out that mine is version 1.0 - 1.1 doesn't use the mini pci slot.

The odd thing is that my psu is hitting over 5 volts - so i doubt that this is my problem.

I'm going to take my router and the power supply to radioshack and have them test in the store the power supply to see if it fixes my problem before i even pay for it.

Just as a note to all - when it comes to power supplys - voltage is the important thing - Amperage is important -b ut only as a requirement for the minimum.

2 amps is the max current that the current psu will allow - but if you find a power supply with 5 volts and 15amps - that will work too - because the unit is only pulling a max of 2 amps.

Keep that in mind when shopping around.

I'll let you guys know what the status is after i get back.

[gonzo0815]

Re: Failed Linksys WRT54G router (newbie)

Well, i think 4,5v isn`t that great, asuming that the smps circuit want to have some 5v. may be you can add an capazitor direcktly on the power lead of tyour wallplug. Or hold it at the inputconector of the wrt. If you see some light, you have the cause for no operation.
Adding some big caps will increase the voltage of most DC wallplugs and stabilizing it.

[cassetti]

Re: Failed Linksys WRT54G router (newbie)

FIXED IT!!

I went to radioshack - and got a 6 volt 1.8 amp output - tested it in the store - it worked.

I'm going to run this until i can get an exact replacement for mine - seems that while the power supply had 5+ volts going to the plug that goes into the unit, there must have been another problem that could not be seen on a $30 multimeter. I paid $24 for this psu - but thats too expensive - i know i can get a direct replacement for under $15 from linksys - so i got 30 days to return this one to radioshack.

Thanks all!

[lfuller1]

Re: Failed Linksys WRT54G router (newbie)

Go to All Electronics

http://www.allelectronics.com/cgi-bi...R_SUPPLY_.html


This is what I ordered for my WRT54G v1 power supply:

Item: PS-537 Price: $ 4.75
- 5VDC 3.7A SWITCHING POWER SUPPLY

It works like a champ and the price is right..

LF

[paranut]

Re: Failed Linksys WRT54G router (newbie)

Thanks for the info LF.

I thought my v1.0 was a goner too and also suspected the caps. I had the Power (green LED) and Diag (red LED) permanently lit so assumed the PSU was ok. Just to be sure though, I tried a different PSU and would you believe it, it now works OK!

I had a 5.0V, 2.0A PSU lying around (better quality from HP) so I swapped the cables over and will now use that. I figure that as it lasted for 6 or 7 years, it'll last another 6 or 7 on the new PSU. ;-) That's saved my blowing a wad of cash as the last one, despite being a lowly V1.0, has worked great for years!

Cheers
Brett

[Krankshaft]

Re: Failed Linksys WRT54G router (newbie)

While I hate to rise this post from the dead all of my Linksys routers and print servers use either linear or switch mode voltage regulators at the input.

So an extra volt really doesn't matter. The regulator will just step it down anyways.

On a side note my Linksys BEFSR41 randomly crashed for years. Once a month or every few months just enough to be annoying. It was supplied by the stock a 9 volt AC adapter.

Inside the router it was rectified and applied to a voltage regulator.

So one day I plug the adapter into my variac and turn down the voltage to see when it would crash (the diag light would come on). Suprisingly enough it crashed just 6 volts under line voltage!!! It is very possible for line voltage to drop once in a blue moon like that.

So I replaced it with an extra Phihong 1 amp 9 volt switcher I purchased awhile back and it hasn't crashed since. As a matter of fact after the PWM is kicked on the switcher functioned down to 25 volts! The adapter utilizes an efficient TOP IC so I'm not suprised.

Below 25 volts the router cut off entirely and didn't DIAG like before.