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Old 06-11-2013, 10:30 PM   #1
nitelite
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Default Linksys PAP2 - Loud Static

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?
Attached Images
File Type: jpg pap2TOP.jpg (1.57 MB, 169 views)
File Type: jpg pap2BOT.jpg (1.87 MB, 122 views)
File Type: jpg pap2OHMS.jpg (992.9 KB, 97 views)
File Type: jpg pap2LOC.jpg (995.6 KB, 86 views)
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Old 06-26-2013, 03:29 PM   #2
nitelite
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Default Re: Linksys PAP2 - Loud Static

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
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Old 07-02-2013, 10:11 AM   #3
ben7
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Default Re: Linksys PAP2 - Loud Static

Quote:
Originally Posted by nitelite View Post
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
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Old 01-24-2014, 05:02 PM   #4
kleung
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Default Re: Linksys PAP2 - Loud Static

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.
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Old 11-07-2014, 12:52 PM   #5
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Default Re: Linksys PAP2 - Loud Static

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.
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Old 01-19-2019, 02:58 PM   #6
siggi
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Default Re: Linksys PAP2 - Loud Static

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.
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Old 12-11-2020, 09:31 PM   #7
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Default Re: Linksys PAP2 - Loud Static

On my PAP2T I had been experiencing crackling/popping noises when on a call and over time it started boot looping.

The boot looping I narrowed down to the AC adapter fairly quickly. Both output caps were shot. Tried replacing them at first, though that repair was ultimately in vain. Unloaded I tested it with a DMM and was putting out 5V. But once loaded the voltage would either drop to ~2V or go dead completely. In short, after ~10 years of service it likely isn't worth trying to repair, just replace it.

With a new power adapter the original audio issue still persisted. Had the VOIP adapter opened up, all caps looked OK. Tried changing the main input cap first for the hell of it. Tested with ESR meter and surprisingly was still good but with age might as well put a fresh one in anyway. Didn't help with the issue though. Finally ended up pulling all of them. Bit of a pain since the ground planes are so large on the board. Had to use both hot air to preheat the board along with the iron to get them out. What ended up causing the issue for me were the two CapXon 27uF 100v caps. Despite looking perfectly normal and even still measuring ~ 23uF, the ESR was ~100ohms for one and over 1kOhm for the other. Replaced hundreds of caps over the years bet never seen them fail in that way before; with capacitance still OK but ESR through the roof. The other low value 16V caps were fine though. I'll probably swap them out later anyway to be safe but I just don't keep keep stuff that low value on hand. Failure rate is just too low.

Another symptom I noticed before the repair was the board had been running hot in a particular area above the pair of SMD coils (center RH side, note Rogfanther's picture.). Couldn't narrow down which component though since just touching the area was enough to make it crash go cold and would have to reset it each time for it to happen again. But after the repair that area would just be normally warm.

Certainly not the only failure points but this was my experience with the device. And whenever I see a CapXon on any repair I do a replacement is almost always warranted. Considered upgrading to the SPA112 but those have shot up in $ lately and reviews seem to say while it may be more efficient it's also under-powered. Other people who've had both preferred the original. Just assume keep this one up and going as long as possible.
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Old 07-29-2021, 11:52 PM   #8
rjd
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Default Re: Linksys PAP2 - Loud Static

My Pap2t has had noise problems for a long time, then the other day the caller ID stopped working - phones plugged into it just say "DATA ERROR". I tried multiple phones - they all exhibit the same issue.

I replaced all 8 of the electrolytic caps and this cleared up the noise - sound is perfect now - but the Called ID did not get better.

Does anyone have any information on this device as to which transistor(s) drive the called id onto the line?
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