Linksys PAP2 - Loud Static

[nitelite]

Since I found only one other PAP2 thread with no pics I thought I would add one for the record.

Linksys PAP2 VOIP adapter had dialtone but with loud static noise. All caps are Teapo execept the two 27uFx100v which are Capxon. LOC pic has datasheet info if you can read my scratches. OHMS pic has readings to ground at top left screw hole in ohms. The readings are rounded a little but should still be usable.

Started with visual inspection - all caps/everything looked normal to me. Plugged in power supply and felt for hotspots and found one! Started measuring ohms and looks like Q156 is shorted to me. Q164 has one odd reading but probably affected by shorted Q156?

[nitelite]

I decided to only replace the caps and Q156. After initial power up static was gone and it seemed to work well. Then I picked up the board and some static returned.

Rats! I must have missed something or the other transistor might have a problem. I thought about it a while and remembered how hot the board was because of the shorted transistor. I hoped it was just a cracked solder joint or two from the heat so I touched the iron to nearby joints and rechecked my work for stray solder/whiskers. Not sure which it was, but now it has been working 24/7 for about a week.

Success

[ben7]

Originally Posted by nitelite

I decided to only replace the caps and Q156. After initial power up static was gone and it seemed to work well. Then I picked up the board and some static returned.

Rats! I must have missed something or the other transistor might have a problem. I thought about it a while and remembered how hot the board was because of the shorted transistor. I hoped it was just a cracked solder joint or two from the heat so I touched the iron to nearby joints and rechecked my work for stray solder/whiskers. Not sure which it was, but now it has been working 24/7 for about a week.

Success

Yep, bad connections can cause hiss, pops, thumps, cracks, buzzes... all sorts of strange stuff :O

[kleung]

just a quick update.

I have a Linksys SPA2102 @ the office that was running continuously from May 2008.

The PAP2 quality isn't that great (may be the provider) but I finally took the device apart for a quick inspection.

Caps are visually good and are CapXphon branded for all of them.

[rogfanther]

Hello, just to register this here.

Got one that would keep rebooting continuously. Red light, lan light, all lights on, then go over it again. The caps in the input side of power supply were ok.

Could not get readings in the 1117´s, because the unit seemed to reset the power circuits.

Inspired by an youtube video, discovered one of the coils open in the areas circled in red. Changed that, and the thing got to work again.

I´ve edited nitelite´s picture to show where.

[siggi]

My VoIP recently stopped working. Comically nobody's sure when it died, as we really don't get that many calls on the "landline", and it faults over to a mobile anyway.
Since we recently changed internet providers, I initially suspected the new one of blocking or interfering with our VoIP. However, after a closer look, it turned out the PAP2 is in a reboot loop, so I opened it up.
First order of business was to change the main 5V filter cap, as it was visibly bulging, but that still didn't fix it. Measuring over the 100V caps I found that only one of them had a voltage across it. I measured the three 10uF/35V caps all bad, so I changed those too - two of those are bulk storage for the HV/Ring supplies. No change.
By comparing the two HV/Ring supplies, I eventually found that the SMD fuse was blown for one of them. Bridging it will bring the supply up and stop the reboot loop. These look to be 1.5A, presumably fast blow 0603 fuses (marking "K"), so I'm going to order some of those in, replace the remaining electrolytics and press this old faithful back into service.
I should note that all the electrolytics measure either flat out dead, or well under spec. I guess this is to be expected for a unit that's been running continuously since 2005 or so.