Linksys WPS54G with mystery caps?

[AlmightyOatmeal]

This is my second time typing this, apparently I accidentally hit a key to close the firefox tab thus losing my previous post... Here we go again:

I was given a Linksys WPS54G print server. Upon plugging it in, I'm getting inconsistent results. Usually it ends up with the USB LED being illuminated then doing dim then either going out completely or next to no illumination. The power LED never illuminates.

The power supply is 5V @ 2A. I measure 5V under no load so I tried this adapter in a Linksys VoIP adapter and that seemed to turn on so I'm assuming it's the print server itself.

After opening it, I measured ~2.7V at the barrel connector posts. I get a similar reading at the AZ1084 (3.3V) regulator. I'm assuming it's a cap before the regulator that could be causing an issue. There are two strange caps I've never seen, maybe a tantalum type cap, but I've been unable to locate specific information. They are yellow rectangles with a prong at either long end. There is an orange band at the top followed by 3 lines of "107", "16" with a small 'k' with a horizontal line above and below that letter, and "451".

I'm assuming it would be the mystery cap pre voltage regulator, but I'm not sure. It acts as if something is shorted. Any information or advice would be more than welcomed!

[Toasty]

Re: Linksys WPS54G with mystery caps?

Photos?

Sounds like an overload and it's killing the 5v input. Could be a bad AZ1084 regulator.

The caps sound like interference suppressor filters. Not a likely problem source at such a low voltage.

[AlmightyOatmeal]

Re: Linksys WPS54G with mystery caps?

The regulator tested out fine, seemed unlikely that could have been the problem. Turns out that it was the power supply itself. I had a duplicate that I replaced the barrel on and it works like a champ. I will tear the power brick apart and try to fix, probably a bad cap or two in there. Only time will tell... ^.^

[AlmightyOatmeal]

Re: Linksys WPS54G with mystery caps? [RESOLVED]

It was one bad capacitor in the power brick. Here is what I did.

The hard part is to open the shell. I placed it on one side and used a really sturdy knife, placing it on the seam in the middle of the device, and giving it a good solid smack with my hand. What will happen is it should make a small incision in the plastic. Be careful not to go too far in or you could damage components. My knife went in maybe 1/8", just enough to break the plastic. I worked forward toward the AC plug (not many full height components near there), and make sure to get that corner, it's crucial. Then flip it over and do the other side the same way, start from the middle in the seam and work ward the AC plug. Once that is done, you should be able use the knife and pry upward to pop the case apart.

The DC power cable and AC plug are somewhat modular, they have mounts that slide in and out of the shell once it is apart. The circuit board itself is tightly fit in one side of the shell, take that knife and gently wedge it between the plastic and the board and gently apply pressure to pop the circuit board up. The plastic will give a little, and don't apply too much pressure, you don't want to break anything. Keep working different points gently, and eventually the board will pop up.

My problem was located near the DC side of the power brick (opposite of the AC plug). The bottom right corner, there is a large capacitor that puffed up for me. That is a 25v 330 picofarad capacitor.

Flipping the board over, I located the two terminals for the capacitor. I fired up my soldering iron and grabbed my de-soldering wick. I placed the wick on top of the first terminal and applied my soldering iron to melt and soak up the the melted solder. I repeated the process for the second terminal and the bad cap dropped out.

After rummaging through some of my old circuit scraps, I located a 16v 330 picofarad capacitor and desoldered it. Why did they use a 25v cap is beyond me, that was overkill.

Looking at the cap, locate the longer lead. That is is the positive (+) side, match that with the "+" marking on the circuit board. Once the cap is seated, flip the board over while trying to keep the cap in place (so it doesn't drop out, I used a needle nose pliers to rest act as a support. Fire up the soldering iron again and your solder and resin (or resin core solder), place the solder next to the lead you want to solder and tap it with the iron to get a bead of melted solder on the contact. You don't want to heat up the leg of the cap too much or it will damage the cap due to the short length of the lead. The bead will heat up the small terminal by itself. Make sure not to make a mess, use a huge glob, or short out terminals.

(I did the same thing to the 25v 220 picofarad cap right next to the transformer next to the DC side, should have been glued to the transformer to prevent it from moving. After inspection it was just fine so I re-soldered it in place to give it fresh solder and eliminate a cold solder joint)

I tested the voltage and it was stable at just over 5V both without and with load.

Place the board back in the shell, slide the DC and AC guides in their appropriate place, and I used some "welding glue" on the joints to hold it together. Welding glue is intense when it dries and will bond just about anything, including plastic. I tightly wrapped it with electrical tape until the glue had a chance to dry (about 24 hours).

Sure these power bricks are cheap, but I prefer to save every penny I can and fix/rebuild everything myself. That way I know it was already broken and it was fixed and fixed properly. Hope this helps! Happy soldering!

[Toasty]

Re: Linksys WPS54G with mystery caps?

Excellent! Yet, we still wait for photos.....

FYI -
uF = microfarad
pF = picofarad

>>Why did they use a 25v cap is beyond me, that was overkill.<<
A 25v cap could be (was) cheaper than a 16v cap at production. As long as they get a 15-20% safety margin in voltage, and it fits, it doesn't matter.

Now, if you did not use a low ESR cap in its place, you'll be back in there. These are switching PSU's and require that type of cap. It's what this forum is all about.

Toast

[AlmightyOatmeal]

Re: Linksys WPS54G with mystery caps?

Oh me oh my, such silliness has come from me. I got my micro and pico farad's mixed up. It's been a long week for me. Thank you for point that out.

I don't have photos available which is why I tried to be as descriptive as I can. I could always tear the power supply apart again and setup some shots.

Thanks for the mentioning the ESR, and yes, I did use a low ESR cap from a similar circuit as well.

Thanks for the input! Each time I do something, I'm always learning. I love to share information just as much as I love to share it.

[Toasty]

Re: Linksys WPS54G with mystery caps?

>>...It's been a long week for me.<<
Hey! It's only Thursday. Just think what tomorrow could be like!

Yes, I enjoy your descriptive ramblings...
Do you have them for Kindle???

>>...I did use a low ESR cap from a similar circuit as well<<
Okay. Just wanted to be sure you didn't stick a "Radio Shack Special" cap in there.

Glad you got it fixed. Hope it serves you well.

Toast

[AlmightyOatmeal]

Re: Linksys WPS54G with mystery caps?

>>Yes, I enjoy your descriptive ramblings...
Oh you're such a tease

>>Okay. Just wanted to be sure you didn't stick a "Radio Shack Special" cap in there.
Silliness I do declare! I haven't found myself in a Radio Shack in years. I would rather dig through scraps or wait for a shipment from Digikey or Mouser. I try to stick similar parts from similar types of circuits.. Power supplies to power supplies, RF to RF, etc.

>>Glad you got it fixed. Hope it serves you well.
Well, that reminds me of some more information I should add...

It seems that this WPS54G is one of those Linksys flops as most people say. There are two major problems. 1) Was the "bricking" effect and 2) insanely unstable. Well non firmware related undesired operation where it won't start up is usually due to cheap caps in the device itself or the power supply. Someone else posted about the caps in the device itself which they seemed to have fixed with their original version of the WPS54G because mine looked considerably different than the one posted (sorry for the lack of photos again). I posted about the power supply, so let's talk about something else..

This thing is really unstable, there is no doubt about that, even with the latest firmware. I originally set it up via the downloaded software but had to deal with several lockups. Even using the Web UI I faced several device lockups and had to restart the device. I would recommend using a static entry on your DHCP server or just setting a static IP address. I never did get the client software/drivers to work, but here is what I did to get it running in Windows 7:

I did install the client software which probably has no effect. With the drivers in hand, I went through the "Add Printer" wizard, chose "Network Printer", selected "The printer I want is not listed", selected "Add printer using TCP/IP or hostname", then enter the IP address of the WPS54G (I wouldn't recommend using the hostname due to issues I've had with the firmware), then from here it will probe an analyze the print server. The analysis will be inconclusive, so under "Device Type" choose "Standard" then "Network Print Server (1 Port - USB). It will continue to try to communicate with the print server and detect what printer driver to use for the connected printer, if it doesn't automatically install, select the printer or point it to the drivers for the printer. Straight forward.

For those more advanced users, it's a standard TCP/IP port to <ip address of the print server>, port 9100, using the RAW (not LPR) format.

Without using the linksys client side software or drivers, without messing with the web UI, and using this installation method on my client machines.. This print server has actually been quite reliable and stable.

I know this doesn't belong here per say, but this will eventually get scooped up by search engines so I might as well provide as much information in one area as I can. Plus extra publicity.

[cheapie]

Re: Linksys WPS54G with mystery caps?

I accidentally hit a key to close the firefox tab thus losing my previous post...

For future reference, Ctrl+Shift+T will reopen a closed tab.