ZyXel Router

[thewizz]

Hi all! This is my first real post here (besides my hello post).

I'm not sure if this is the right place to post this or not, but its not really a mother board but kinda is a mother board. Anyway....

I just purchased this off an auction site that will remain nameless... When I got it, it was DOA. So, I pulled it apart to find a bad Cap and resistor. Now I just need to figure out what they are so I can replace them and hopefully get this thing running again.

The parts in question are C9 and R27. C5 is right next to C9 but it does not appear there was anything there to start with, but I would like to confirm that.

I am attaching several pics of the board, to hopefully help.







I appreciate any help!

Thank you!

[stj]

Re: ZyXel Router

post a more zoomed out foto,

[Agent24]

Re: ZyXel Router

What is the model number of the router?

Can you give a photo showing the entire board (both sides)?

[thewizz]

Re: ZyXel Router

Thanks for the replies!

Agent24; the model is SyWall USG 50

Agent24/stj; I have attached some larger pics of the whole board and a more zoomed out of the specific area.

Thanks again!

[Per Hansson]

Re: ZyXel Router

Is that the WAN port?
Does the router power on and work at all?
Because if only those resistors and caps where hit it would still work.
Just without the WAN port that is, but looks like lighting damage so could be more stuff dead...

[thewizz]

Re: ZyXel Router

Is that the WAN port?
Does the router power on and work at all?
Because if only those resistors and caps where hit it would still work.
Just without the WAN port that is, but looks like lighting damage so could be more stuff dead...

Yes, those are the WAN ports (there are 2).

Yes, it powers on but that is about it.

When I plug into any of the 4 ports the green light comes on steady, like there is no communication going on.

When I try to ping the default address (192.168.1.1) the response varies. Sometimes it simply times out others I get "Destination host unreachable" then it will show ie: packets: Sent = 4, Received = 2, Lost = 2 (50% loss). So, it seems like it is trying to communicate...

When I attach my cable modem/router to one of the WAN ports it will pass through and assign an IP address to my computer and I can communicate through it but not to it.

I have tried to reset it by holding the reset down and waiting for the power light to blink but it never blinks.

The CPU runs very hot. I have tried putting a fan on it to keep it cooler but that makes no difference (besides keeping the heat sink cooler).

Yes, it is very possible there is more wrong than just the 1 cap and resistor. Thought that might give me someplace to start though.

Thanks!

[Agent24]

Re: ZyXel Router

At a wild guess, C1 and R28 on the other side of U3 are probably the same value as C9 and R27. So at least you can probably test those and find out what you need as replacement.
If you can look up the FCC ID on the FCC website you might get lucky and find the BOM.

That you get some ping response is promising, but if it is a lightning-strike victim... that's like ESD, it could cause all manner of weird damage.


"Very hot" is subjective. Do you have a temperature probe? Some things do run pretty hot by design. The manufacturers want as much money as possible and usually don't spare the expense of a heatsink unless they have to. 50-60*C is pretty hot to the touch, but most chips like this will operate just fine running that hot. Whether they should do, is a different question...

That said, if it's super hot, it may have some internal shorts, or a voltage regulator has failed and it's getting too much voltage. Though I wouldn't expect the thing to respond to ping requests if it was in that bad shape.


At this point I would replace C9 and R27 and see what happens, but don't hold your breath. Clean the board well. Carbon is conductive. I hope it's not burned too badly.

I also wonder about U43 on the bottom side, it seems to have a spot which could be a burn\heat mark, or maybe just flux residue. Hard to tell.


If it still doesn't work, you need to find and check all the voltage rails to start with. Other than that, I don't know there's much you can do on something like this without a schematic or at very least a working unit to compare to.

[thewizz]

Re: ZyXel Router

Agent24, Thanks again for your help!

I probed the heat sink and within about 1-2min it was over 100C. Yeah, HOT...

U43 appears to be fine. Probably just the pic.

If the unit did get zapped by lightning an internal short in the CPU would not be surprising I guess. I will try and track down the voltage paths but that will be challenging without a schematic...

I was looking a little closer and noticed that there is a burnt trace that goes under the module beside R27. I guess that means I am going to have to pull the module off to repair the trace.

I also noticed that R26 looks burnt (guess that makes sense).

I attached a close up of the area.

This may be a stupid question, but I have never tried to look up a BOM from the FCC's web site. How would I go about that? I'm assuming there is probably a post on this site. I will try and find one.

Thanks again for the help!

[Agent24]

Re: ZyXel Router

That sounds far too hot indeed! I would have doubts about the CPU being in a healthy state if it heats up that much.

I mistakenly misled you about the FCC ID. You could look them up here, https://www.fcc.gov/oet/ea/fccid but this machine won't have an ID since it has no wireless interface. For some reason I thought it had WiFi. Sorry!

[thewizz]

Re: ZyXel Router

That sounds far too hot indeed! I would have doubts about the CPU being in a healthy state if it heats up that much.

Yeah, I think I'm giving up on it. I don't really feel like doing as much work as it seems like I need to do, just to find out the CPU is dead.
I've gone back to the auction site and entered a complaint. We will see if that does anything... Doubtful! If not, I really didn't pay all that much for it so I'm not out a lot.

I mistakenly misled you about the FCC ID. You could look them up here, https://www.fcc.gov/oet/ea/fccid but this machine won't have an ID since it has no wireless interface. For some reason I thought it had WiFi. Sorry!

That's cool. I actually went and started searching the fcc site and was noticing that it seemed to all be wifi related items.

Thanks for all the help! I really appreciate it!