Linksys BEFSR41 Red light o'death

[golemmaster]

I know these routers, like many things, have bad capacitor issues.
When my router started self resetting and finally gave the continuous red Diag light symptom, I decided to pop it open and snoop around.
I don't have a ESR meter so I blindly replaced the D-paston caps. No change. I checked the output of the bridge rectumfire. Input of 12VAC output 9.5VDC. Is that much loss normal?
I understand new routers are cheap. I wanna try to fix this one.

Any suggestions or experience in fixing one of these?

 

[Hero999]

What's a rectumfire? Is that when you have piles?

 

[golemmaster]

Rectum? It nearly KILLED'EM.
lol. just making a joke. Of course I mean Rectifier.

 

[user_88]

Not sure if this is relevant ....I have the same router ....BEFSR41. It was giving me some trouble .... The problem seemed to be that the unit was overheating. I had stacked it on top of the mating Linksys cable modem, and apparently there wasn't enough air flow to adequately cool the unit. I separated the router and the modem, and the problem disappeared immediately ... no further issues.
Just something to try out .....

 

[golemmaster]

I am not sure how I botched testing the rectifier. Turns out it's fine.
At first I just changed the two big filter and smoothing capacitors. That didn't fix it.
There are other small caps on the board. Like 22uf 16V and such. I pulled something close to that out of my scavenged cap stash. I went around touching the leads to the bottom side of the installed caps. One of them I touched... The router woke up! Red light went out and seemed to function. I desoldered it and replaced it.
I don't have an ESR meter. The only thing I could think of to check caps is to set my DMM to diode test beep. I touch the leads of a cap and if I hear a brief "blip" that means it is not open or short and is charging. Then I switch over to DC voltage check and watch how fast it discharges.
The cap I replaced was open. I started probing around and found another cap that didn't "blip" (open). Replaced that one too.

The router seems to function. Need to test it for a while before I pat myself on the back.



---------------------------
cap cap cap cap cap cap I said "cap" too many times.

 

[Mikebits]

Check the AC adapter, they are low quality and fail often. Before you buy a new router or tear into your current one, verify AC adapter is working.

---------------edit----------------
Advice too late I guess as you already have fiddled with the board. I would still venture to guess the AC adapter.

 

[golemmaster]

Although the AC adapter is rated to output 9VAC, it's actually putting out about 12VAC. It is working though.

I forgot my DMM is able to test small <20uf capacitors. I tested the ones I removed. They are supposedly good but it's hard to argue with the process of elimination. I don't get it...but the router is working.

 

[golemmaster]

BEFSR41 on top of my BEFCMU10

Not sure if this is relevant ....I have the same router ....BEFSR41. It was giving me some trouble .... The problem seemed to be that the unit was overheating. I had stacked it on top of the mating Linksys cable modem, and apparently there wasn't enough air flow to adequately cool the unit. I separated the router and the modem, and the problem disappeared immediately ... no further issues.
Just something to try out .....

I have the exact same arrangement. BEFSR41 on top of my BEFCMU10 cable modem. While they do get warm, I believe the issue is the capacitors that go bad.

 

[user_88]

I have the exact same arrangement. BEFSR41 on top of my BEFCMU10 cable modem. While they do get warm, I believe the issue is the capacitors that go bad.

Sounds plausible ..... My router and modem are probably 10 years old .... getting into the era of aging components ... Difficult to pinpoint exactly what is wrong. .... Maybe try a little of the canned chiller spray on individual parts to try to diagnose the particular part that is causing the difficulty.

 

[Mikebits]

Although the AC adapter is rated to output 9VAC, it's actually putting out about 12VAC. It is working though.

I forgot my DMM is able to test small <20uf capacitors. I tested the ones I removed. They are supposedly good but it's hard to argue with the process of elimination. I don't get it...but the router is working.

It is AC ripple that causes the fail mode. You need a scope or try another adapter.

 

[golemmaster]

It is AC ripple that causes the fail mode. You need a scope or try another adapter.

Must be a pretty bad ripple. Before (and after) I started messing with caps I did try a DC adapter. It didn't change anything.

I have to admit the router still isn't perfect. I still have some detective work to do. Performance/throughput is bad. Even logging into it's own web-based settings is slow and pages don't load completely.
I didn't replace all the capacitors. Only the ones that are known to go bad (filters) and could identify as bad with my piss-poor technique.

I'm trying. I'm learning.
Real equipment would be nice.

 

[golemmaster]

Well.... just to update. I want to get some test equipment before working on the routers and other things I have started to collect.
I have a box of scavenged capacitors that need testing and a bunch of dead/bad motherboards that I might scavenge more parts from.
Hopefully the **broken link removed**.
But might fall back on the Blue ESR because it's probably easier to obtain.
I'll just dream about getting a scope. I got some learning to do before I could put it to good use anyway.
For a long time I've been using a butane iron. No cord to deal with and gets good and hot. No risk of voltage leakage from the tip. If the butane iron is a terrible idea, let me know and why.

Thanks. More later.