Netgear DG834GT badcap repair

[philpem]

From my fault log, hope this is some use:

Device: Netgear DG834GT ADSL2+ 802.11g Wireless Router, manufactured late 2006/early 2007.

Failure mode: Power on, two orange blinks from TEST LED, WiFi LED flickering, LAN switch functions seemingly OK, but no access to web interface, ADSL connection apparently down, and obviously no routing function. Accompanied by loud audible whine/whistle, like a switchmode PSU that's running out of regulation. Unit previously known to have poor WiFi signal strength/quality.

Cause of failure: Multiple.
5x defective TEAPO alu-electrolytic capacitors. Two showing visible bulging on top safety vent, one visibly expanded in middle. Safety vents A-OK on all, no visible leakage. Some visible heat damage to most of central area of PCB.
Multiple poor quality solder joints on SMPSU inductors, Ethernet connector shields and ADSL line protective spark gap.

Repair instructions: Replace following:
i. 100uF 25V x1, 2.5mm pin pitch, diameter 6mm. Close fit, very little room around component.
ii. 470uF 16V x1, 3.5mm pitch, 8mm dia
iii. 1000uF 16V x2, 5mm pitch, 10mm dia
iv. 1000uF 6.3V x1, green label Low ESR, 3.5mm pitch, 8mm dia

Suggested replacement parts:
i. Panasonic EEUFM1E101 (100uF 25V)
ii. Panasonic EEUFM1E471L (470uF 25V, uprated replacement)
iii and iv. Panasonic EEUFM1C102 (1000uF 16V, uprated replacement)

There is enough room on the board for the taller Panasonic parts, esp. in case of iv.

Also resolder:
All power inductors.
DSL line protective spark gap
RJ45 connector shields

Final repair state: Unit functionality restored. Some remaining whistling/whining, may be permanent damage to inductors. Taller replacement capacitors make case slightly difficult to close.

Notes:
Case screws require Torx T-8 screwdriver to remove. All 4x located under rubber feet on base of '834GT unit.

[philpem]

Re: Netgear DG834GT badcap repair

Another point about the 834GT - typically, when the caps go the glue holding the inductors down will also have gone slightly conductive. This throws the SMPSU out of whack -- not enough to throw the PSU out of regulation, but enough to make the thing hiss like mad.

Solution is to desolder both of the large power inductors, remove the white glue (to the point of scraping it off the PCB and washing it down with isopropyl to get rid of the residue), scrape it off the inductor leads, then solder the inductors back down. Also clean off as much solder flux as you can (>90% isopropyl again).

There are also two small black inductors (labelled 2R2 or something like that IIRC) near the power supply circuitry. Resolder these too, but you don't need to (and probably won't be able to) remove them.

This and the badcap replacement has stopped my 834GT hissing and squealing when the WiFi is in use. Can't really comment on sync speeds, but it was syncing at 10.8Mbit or so downstream before I redid the inductors, and now syncs at just under 11Mbit. That could be normal line condition variation though.

Lastly, the small white rubber feet are easy to lose. Best plan is to take all four out, then put them in a box or small plastic bag until you've finished repairing the router...