Fix a WNR854T with the GLOD Problem

GLOD = Green Light of Death

Apparently some WNR854T suffer from this problem acc. to this forum thread. The device suddenly breaks down (after a couple of weeks or months), only the power LED remains on. Sometimes the device powers up correctly after the WLAN miniPCI card was removed.

This page assumes some soldering skills. You may break your device and of course void any guarantee! Furthermore you need a new switching regulator which fits into the case. I've used an Austin PicoTlynx APXS003A0X-SRZ (e.g. from mouser.com).

When opening the case be careful with the cables to the three internal antennas. See this article for some hints.

I've got three broken WNR854T, all had a broken 3.3V power regulator on board. Just measure the voltage on the capacitor C524 (while the miniPCI WLAN card is attached to the PCB), it shall be 3.3V (+/- 5%). If it is, your problem has another cause and this page cannot help you, sorry!

Check the voltage on capacitor C519. It shall be 5V. If not, don't continue, either the 12→5V switch regulator is broken or the 5V supply has a short.

I removed the whole 3.3V circuitry except the ceramic capacitors C523, C518. The holes of C524, C519 are used to connect the new regulator to the board. C536, C527 belong to another regulator. Getting rid of the IC was difficult as the soldering pads are hidden below the housing. I used hot air.

I put a 2.15 kOhm (+/- 1%, metallic) Rtrim on the PicoTlynx between TRIM and GND. I mounted the PicoTlynx in an upright position, attached the three pads VOUT, GND and VIN with short wires to the corresponding holes of C524 and C519. I added two capacitors 22uF/35V to the pads of the remaining C523,C518.

The PicoTlynx seems to work fine without RTUNE and CTUNE.

This procedures revived three WNR-854T. The PicoTlynx is small enough to fit the PCB back into the case.

The area inside the red lines is the 3.3V on-board regulator. Unfortunately this picture was taken after the modification, i.e. it doesn't contain the original components: .

The IC in the original regulator seems to be a Marvell 88PG877.