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Author Topic: A Problem for A Real Expert - the Haunted Router(s)  (Read 8825 times)

raybeere

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A Problem for A Real Expert - the Haunted Router(s)
« on: July 14, 2009, 02:04:27 PM »
Sorry; I'm going to have to go into a bit of detail here, as I have no idea what might make a difference.

My computer system as I have it set up and connected to the Internet dates from spring 2006; the computer is a bit older but the setup was different and probably does not affect this problem. In 3+ years, I've been through three routers, about to find it necessary to buy #4 if I can't fix this one. (Still working, but past experience suggests it won't be long.)

First router: a cheap Belkin. I worked okay for about two years. Then, one day when I tried to access an unavailable site, the "wrong" DNS page popped up. I'd set my router to use OpenDNS, I got my ISP's version instead. So I accessed the router's settings and discovered something had messed them up (I assumed - and still do - heavy electrical storms not long before might be to blame). Fixed them. Very strange things started happening on my system: I didn't suspect the router, since most of the issues involved programs that were (at best) peripherally connected. I thought it must be malware, so I tried scanner after scanner with no real result (one or two advertising cookies, a key in my Registry that was adware, nothing extreme - and nothing that fixed the problem). I started having Internet connection problems, tried to access the router's settings again - and couldn't even get the login page to come up. Soon after, the router died. Total brick, so I tossed it and picked up a replacement. All problems, including what I'd thought must be a malware infestation, cleared up immediately.

Second router, the replacement, was a cheap Netgear, the first thing I could find on a store shelf, since I wanted to get back online. :) After less than a year, there was an incident with non-computer equipment on the same circuit. A fuse blew, and the ground-fault interrupter I have my surge protectors plugged into tripped. I started having connection problems (w/o too much strangeness; there's enough junk on my system it is hard to be sure what is due to those issues and what is a real problem - I know, one of these days I'm going to have to bite the bullet and reinstall). I didn't want to have to rush out to get another one this time and cash wasn't too tight at the time, so I didn't wait to see if it would die. I looked around, decided what I wanted, and ordered a nice Linksys WRT54GL. :D

Third - current - router: the Linksys. I was meaning to install open source firmware, but never got around to doing that, so it is 'out-of-the-box' except for changes to the settings. A week or so ago, we had a bad electrical storm come through (we've had an unusual number of strikes for the area this year). I pulled out my computer's power, but my son insisted he had to stay connected, so I left the router plugged in and on. (And connected to my computer, which seems fine.) I started having weird things happen on my system. Again, nothing that would point to the router. Then, I got messages about trouble with the Internet connection (still working, but apparently bothering some of the stuff I run). I tried to access the settings: again, I can't get the login page to even come up. "Firefox can't establish a connection to the server at 10.10.10.1" (I know this is not Linksys' default: had to set it to this to get it to work with the modem my ISP provided). I pinged 10.10.10.1 and got the following results:

(Last night)
Reply from 10.10.10.1: bytes=32 time=1ms TTL=64
Reply from 10.10.10.1: bytes=32 time<1ms TTL=64
Reply from 10.10.10.1: bytes=32 time<1ms TTL=64
Reply from 10.10.10.1: bytes=32 time<1ms TTL=64

Ping statistics for 10.10.10.1: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 1 ms, Average = 0ms

(Just now)
Reply from 10.10.10.1: bytes=32 time=2ms TTL=64
Reply from 10.10.10.1: bytes=32 time<1ms TTL=64
Reply from 10.10.10.1: bytes=32 time<1ms TTL=64
Reply from 10.10.10.1: bytes=32 time<1ms TTL=64

Ping statistics for 10.10.10.1: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds: Minimum = 0ms, Maximum = 2 ms, Average = 0ms

I'm concerned that the first result seems to be slowing down, but don't know for certain if this means anything. I think the fact the first result is the slowest is normal, but beyond that, I can't figure this out. Why can't I access the control settings? Is there an alternate way to do this? (Yes, I'd try Googling, but time online may be limited, so I'm trying all approaches, and didn't want to waste time on a search before at least posting here.)

More importantly, why do routers keep dying on me? Yes, there is the lightning - but the modem is plugged in to the same surge protector, which seems to have protected it. (True, I don't know if I'll have trouble with the modem this time, but both other times, replacing the router fixed every problem.) My other gear is in a separate surge protector, and none of it is having trouble.

I've thought about the factors I know affect routers, and this is all I can come up with:

Heat: yes, I do have all this stuff in a computer "armoire" (I have cats :D ) so ventilation is not perfect. Yet the computer runs hotter than the router, yet has no trouble, and has never overheated. (HDD is the only monitor I have, never above 60 degrees C, and usually not above 55 C). Even when the vents in the computer's case became clogged with dust, and the fan was howling like a jet all the time, things stayed fine until I could make the time to go in there and clean it out. And the Linksys has the best ventilated case of the three models that have died, yet it lasted the least amount of time. So I find it hard to believe heat is the culprit.

"Dirty" power: Thanks the most absurd house wiring layout I've ever seen, I have no choice but to have all this stuff on the same circuit as the refrigerator. Sigh. I know that isn't great - but, again, why just the router? Why isn't anything else having problems? (In all that time, I lost one cheap printer that was already on its way out - to a clogged print head. That's it, except for the routers.) So, not good, I agree (and if anyone has cheap suggestions for improving the situation, I'm all ears), but that doesn't seem right, either.

Power surges / lightning: In two of three cases, there was a bad storm right before I started noticing any weirdness. Both of these cases acted very much the same. In the third case, there was an incident which blew a fuse / tripped my GFI. This acted a bit differently, but the connection was utterly clear in this case. So that would seem to be the issue - but then why don't I need a new modem as well? One router might just be bad, but three? From different manufacturers?

I have no idea if I'll have a chance to read them before my router turns into a brick, but any and all thoughts would be appreciated, on the general issue of what might be causing such a failure rate for routers in specific, or on how I might get into my settings and perhaps fix whatever is wrong (I think I'd try re-flashing the firmware, to see if that did any good) before I lose this one. Thanks in advance.

4wd

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #1 on: July 14, 2009, 03:18:44 PM »
Since you seem to be in the middle of Lightning Central, the most obvious question would seem to be:

Does your phone line go through a surge protector/lightning arrestor?

You've mentioned that the modem is plugged into a surge protector but that still leaves umpteen kilometers of phone line for strikes to induce into.

If the phone company deems it necessary to put gas arrestors on every line to protect their equipment, (and it's still no guarantee of protection), then is there a reason why you shouldn't think the same?

Next time your son insists he has to stay connected against your better judgment, ask him if he's willing to buy a new router.

Carol Haynes

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #2 on: July 14, 2009, 03:30:01 PM »
Have you tried hard resetting the router back to factory settings and then setting up again?

Switch on and then press and hold the reset button for at least 30 seconds. Connect the router by a cable to your computer and then try IPCONFIG /ALL from a command prompt. If IPCONFIG says the router is at 192.168.0.1 you are probably back to square one, go to http://192.168.0.1 and login to the router control panel (admin / password) and resetup all your settings.

Once you have it all working again you can go into the router (at what ever IP address you specified) and backup your router settings to your hard disk then if it happens again in the future you can reset the router and simply restore the settings from the router control panel.

If none of this works don't pass go, don't collect $200, nip down to the local computer store and buy a new router.

While you are at it buy a very expensive surge protector to protect all of your equipment (including your phones lines). Don't buy a cheap one they aren't worth the money. Next time it looks like a storm switch everything off and unplug it from mains and telephone circuits!

Good luck.
« Last Edit: July 14, 2009, 03:32:00 PM by Carol Haynes »

Shades

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #3 on: July 14, 2009, 05:31:45 PM »
Computers, more particularly their power supplies, can actually take a lot of bad treatment like "dirty juice" or even milliseconds of no power at all. Get into the named brands of power supplies (and associated price tag) you will be able to mistreat them even more, but not by much.

Compare this with the warts that normally come with a home router...hence one of the reasons why you have a bigger chance of failure there. 4wd is totally right about the phone line and how it is (electrically) secured. 

cmpm

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #4 on: July 14, 2009, 06:43:03 PM »
Just guessing, I would replace the surge protector, having been tripped even once, sometimes they have lost their usefulness.

Your modem could be internally protected and your router is not.
In general start with the simple solutions and cheapest.
But don't get a cheap surge protector.
A good one will pay for itself many times.

4wd

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #5 on: July 14, 2009, 06:47:20 PM »
Compare this with the warts that normally come with a home router...hence one of the reasons why you have a bigger chance of failure there.

I seem to recall there being some issue with Linksys router power supplies in the past, (eg. failing within months), but I'm not sure whereabouts on the planet and how long ago.

@raybeere: You could also try powering the router off of an equivalently rated supply, (as long as it's not one the previously killed router supplies) - maybe it's original supply took just enough of a hit to make it marginal.

Carol Haynes

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #6 on: July 14, 2009, 07:25:40 PM »
I had a linksys router that started displaying similar symptoms and I am sure it was the power supply dying. (It hadn't been abused by lightening or power surges - at least no more than the rest of my network which runs through APC UPSes). Not had any similar problems since I moved to a Netgear router and switch.

Worth trying an alternative power supply anyway (good point 4wd) just make sure it has the same power rating, tip and polarity!!

raybeere

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #7 on: July 14, 2009, 08:49:02 PM »
Since you seem to be in the middle of Lightning Central, the most obvious question would seem to be:

Does your phone line go through a surge protector/lightning arrestor?

Sorry: I forgot to specify that yes, the line going in to the modem goes through the surge protector. It is one of those ones with eight outlets and a phone line in/out jack.

Next time your son insists he has to stay connected against your better judgment, ask him if he's willing to buy a new router.

Oh, he is going to buy the new router. ;D I'd still like to get to the bottom of this.

raybeere

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #8 on: July 14, 2009, 08:52:52 PM »
I seem to recall there being some issue with Linksys router power supplies in the past, (eg. failing within months), but I'm not sure whereabouts on the planet and how long ago.

@raybeere: You could also try powering the router off of an equivalently rated supply, (as long as it's not one the previously killed router supplies) - maybe it's original supply took just enough of a hit to make it marginal.

I'm trying to understand, but this isn't clear. If the power supply was dying, wouldn't the whole thing fail at once? The router is still working (although on my last ping a few minutes ago, the first ping took 7ms) but I cannot access the control panel at all. Why would the power supply affect this? I was thinking it was more that the firmware was messed up in some way.

raybeere

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #9 on: July 14, 2009, 08:54:41 PM »
Have you tried hard resetting the router back to factory settings and then setting up again?

Switch on and then press and hold the reset button for at least 30 seconds. Connect the router by a cable to your computer and then try IPCONFIG /ALL from a command prompt. If IPCONFIG says the router is at 192.168.0.1 you are probably back to square one, go to http://192.168.0.1 and login to the router control panel (admin / password) and resetup all your settings.

Once you have it all working again you can go into the router (at what ever IP address you specified) and backup your router settings to your hard disk then if it happens again in the future you can reset the router and simply restore the settings from the router control panel.

If none of this works don't pass go, don't collect $200, nip down to the local computer store and buy a new router.

While you are at it buy a very expensive surge protector to protect all of your equipment (including your phones lines). Don't buy a cheap one they aren't worth the money. Next time it looks like a storm switch everything off and unplug it from mains and telephone circuits!

Good luck.

Yes, I've got to find the factory default password first. Or was it blank? Once I look that up, so I know I can get in, I'm going to try resetting to factory defaults. Thanks, I was wondering if that might be an option, but was afraid to mess with it since I'm not as comfortable with routers.

wreckedcarzz

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #10 on: July 14, 2009, 09:15:25 PM »
Computers, more particularly their power supplies, can actually take a lot of bad treatment like "dirty juice" or even milliseconds of no power at all. Get into the named brands of power supplies (and associated price tag) you will be able to mistreat them even more, but not by much.

My computer has a nameless basic power supply, giving out 700W of juice. It has withstood about 5 seconds without power, and the computer didn't even flinch. (This was during a strange, short power outage where we lost power for ~5 seconds, it returned, then about 10 seconds later we lost it for about 8-9, and it ALMOST made it... not quite though)

I have a Linksys WRT350N v1 currently, with a WRT300N v1 that was retired due to wifi issues that we're becoming a problem (along with the fact that I wanted the 350, and if I want it then it must be for the better of the family ;)). Our original Linksys, WRT54G v4, still goes strong (as does the 300 now, the issues stopped (I think it was simply stress + the heat of the modem and itself causing issues - the 350 appears to have better cooling (more open holes)). All of them run DD-WRT firmware as well, and that does seem to keep them running better in both performance and stability than the default Linksys firmware.

FWIW, I have switched the power plugs between the routers (except the 350, it has a specific label saying use ONLY this cable... I doubt it matters, though) with no problems, and we have had several power surges and failures over the years (they are always connected to a surge protector/power strip in my room).

Also, I have found that they can take quite a beating - I use the 54G and 300 for LAN parties at friend's houses, and both in transit and once I've got them setup, they can be hit, sat on, thrown, dropped, and more.... not that I would ADVISE you do any of that, but it has happened.


I would go and grab a new power strip first, and if the problem continues/occurs again, get some ventilation going. I have a computer armoire as well, however my modem and router sit on top of my printer, outside of it. If possible (it may sound somewhat stupid, but it may just work) you might consider buying/using an old 120mm case fan and putting it under/pointing it at the router, and see if that helps - although this would require:
1) the computer tower to have a slot in it that the power cable could fit though
2) the case to be relatively close to the router (or get an extension)
3) the cable to be out of sight for aesthetic purposes (optional, but most people are more picky than I am about stuff like that)

Also: default linksys password is admin/admin, I believe (could also be blank/admin)

4wd

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #11 on: July 14, 2009, 11:06:44 PM »
I seem to recall there being some issue with Linksys router power supplies in the past, (eg. failing within months), but I'm not sure whereabouts on the planet and how long ago.

@raybeere: You could also try powering the router off of an equivalently rated supply, (as long as it's not one the previously killed router supplies) - maybe it's original supply took just enough of a hit to make it marginal.

I'm trying to understand, but this isn't clear. If the power supply was dying, wouldn't the whole thing fail at once? The router is still working (although on my last ping a few minutes ago, the first ping took 7ms) but I cannot access the control panel at all. Why would the power supply affect this? I was thinking it was more that the firmware was messed up in some way.

Sorry, missed the bit about it being a access problem - was thinking more along router failure.

As for a PSU dying completely, that is only one manifestation of any potential fault with them.  It could just be running out of specification, eg. supplying low voltage, low current, intermittent voltage drops, too much ripple, etc, etc.

Depends on the type of PSU, while switchmode are nicely efficient, cool-running and take up less space, there's just something so reliable about a hunk of iron with copper wire wrapped around it when you use a transformer, even though they too are prone to failure.

With the access problem in mind, like Carol said, try a factory reset.  If that didn't work I'd probably stick another power supply on it and/or try a firmware flash via telnet before spending money on another modem/router.

I can recommend Zyxel, [insert deity] knows mine has taken quite a few power brownouts/fluctuations over the last 4 years and it's still going strong :)
« Last Edit: July 14, 2009, 11:16:04 PM by 4wd »

tomos

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #12 on: July 15, 2009, 03:14:15 AM »
Yes, I've got to find the factory default password first. Or was it blank?
in case you cant find it I came across this page yesterday related to routers & skype
Your router is here:-
http://www.portforwa...ys/WRT54GL/Skype.htm
if you scroll down a page or so it says
Quote
By default the username is blank, and the password is admin. Click the Ok button to log in to your router.
dont know if that's dependable - sounds odd - no user name but a password, maybe it should be the other way round :-\

Tom

Carol Haynes

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #13 on: July 15, 2009, 04:31:25 AM »
Oops sorry - misread and gave the Netgear settings above instead of Linksys. The other thing is that the defailt route settings for Linksys are at 192.168.1.1

It's been a while since I used a Linksys router but I seem to rember tomos is correct - no user name and password is admin. If admin doesn't work try password instead.

4wd

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #14 on: July 15, 2009, 05:14:32 AM »
"Dirty" power: Thanks the most absurd house wiring layout I've ever seen, I have no choice but to have all this stuff on the same circuit as the refrigerator. Sigh. I know that isn't great - but, again, why just the router? Why isn't anything else having problems? (In all that time, I lost one cheap printer that was already on its way out - to a clogged print head. That's it, except for the routers.) So, not good, I agree (and if anyone has cheap suggestions for improving the situation, I'm all ears), but that doesn't seem right, either.

Just in regard to your Dirty Power, I take it an extension lead to a GPO on another circuit is out of the question?

Either for the fridge or computer equipment, of course you need to clear the existing fault w.r.t the router before you can try this as a means to prove it one way or the other.

Mind you, as soon as you start using an extension lead nothing will happen.................until the week after you stop using it :D

40hz

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #15 on: July 15, 2009, 07:03:49 AM »
I'm going to have to cast my vote for gradual heat damage being the primary culprit.

Power surges to the actual router shouldn't be too much the issue since your devices all use "wall warts" for their power supply. Although these devices aren't surge suppressors or line voltage conditioners, they do provide a fair amount of protection to the devices they power. So unless they've been damaged, I'd look elsewhere.

If you check the output coming off your router's power supply with a multimeter you should be able to see if the correct voltage is being supplied. I'd be especially on the lookout for specs that read lower rather than higher. Low voltage can often cause a device to run hotter than it should.

The situation could also be brought on purely by environmental heat factors. Either the router is getting too warm by being where it is; or the power adapter is providing the wrong (likely low) voltage since many power devices will produce lower supply voltages when they overheat.

Suggestion: if you do test your adapter, try running it in its normal environment for an hour or two and then try to test it immediately after you disconnect it from the router. If there's a bad voltage condition, brought on by environmental or runtime factors, this will help you catch it.

So either way, I guess I'm going with heat damage as my answer. ;D

Luck! :Thmbsup:




4wd

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #16 on: July 15, 2009, 08:09:47 PM »
If you check the output coming off your router's power supply with a multimeter you should be able to see if the correct voltage is being supplied. I'd be especially on the lookout for specs that read lower rather than higher. Low voltage can often cause a device to run hotter than it should.

...

Suggestion: if you do test your adapter, try running it in its normal environment for an hour or two and then try to test it immediately after you disconnect it from the router. If there's a bad voltage condition, brought on by environmental or runtime factors, this will help you catch it.

According to Linksys' site, the PSU for that router is switchmode so you won't be able to get an accurate reading unless it's under load - and it still won't tell you how much ripple is on the output which is a problem when the capacitors in a switchmode start going high-ESR due to, for example, heat strain and voltage fluctuations.

It would be easier to replace the PSU with a known working one.

Shades

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #17 on: July 15, 2009, 08:26:08 PM »
Now those old but very handy oscilloscopes could come in handy (to find out if and how much dirt the input/output takes and puts out)...too bad they always were so damn expensive, which is also true for the recent digital ones.

40hz

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #18 on: July 15, 2009, 09:32:14 PM »
It would be easier to replace the PSU with a known working one.

True. You could add a dummy load, but that really wouldn't be all that accurate either. Still, a 20Ω @5W or 10W resistor in parallel with the output should provide enough of a load that you could do a quick & dirty multimeter check to see if you're at least in the ballpark.

Then again, it would be easiest to just try a different PSU.

-------------

Sean (one of my hardware tech buddies) pointed me towards this article, which discusses wall warts in detail, along with a project to safely add voltage regulation and filtering to an inexpensive plug-in power module.

Quote
So, since we usually want to power an auxiliary device at a steady specified voltage and since we usually need a very clean power supply, what I wanted Bill’s help on was in creating a filtered, regulated power DC supply. We accomplished this by adding a module between the wall wart and its DC output plug that contained a fixed or adjustable voltage regulator and a network of filter capacitors.


Link to article: http://www.dxing.inf...wall_warts_bryant.dx

The circuit and construction are well within a hobbyist's abilities. Sean swears by the fixed voltage version of this project. He's used it to get solid performance out of otherwise flaky consumer-grade router/switch products.

Might be worth a read. :Thmbsup:

(I'm going wire one up and give it a try on an RVS4000 that's been giving me some intermittent 'attitude.'  I figure it's got to be cheaper than taking a hammer to the little bugger. Which is something I've been tempted to do lately.  ;D)



4wd

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #19 on: July 15, 2009, 10:02:40 PM »
Sean (one of my hardware tech buddies) pointed me towards this article, which discusses wall warts in detail, along with a project to safely add voltage regulation and filtering to an inexpensive plug-in power module.

That article is for your basic transformer style plugpack.  The circuit that is detailed is normally, (just to clarify - if the manufacturer wants a cleaner supply he may incorporate a simple switchmode design in the device itself but generally a lot of equipment uses basic linear regulators, eg. 7805, 7812, etc), what you find connected to the power input socket of the device - so in effect you are connecting another circuit that's the same in series.

The only problem with that is you've just disabled the internal voltage regulating circuit of the device.  The regulators mentioned in that article require at least an input voltage 1.2V above the required output voltage in order to regulate correctly otherwise they just drop out.

eg.  If your device requires 12V DC there will typically be a 7812 regulator connected to it's input power socket - it's relying on the normally unregulated voltage provided by the transformer plugpack of around 16V DC allowing it regulate correctly.

If you build the circuit as described and set its output to 12V DC and then plug that into your device, where does the internal regulator get its required voltage drop in order to regulate?

I would say he has success probably because of the extra filtering he's added by way of the capacitors.

Switchmode PSUs are self-regulating and don't require it, they only require the requisite load for regulation - and the latest versions don't even require that.

EDIT: Also note that article is from 2005, switchmode plugpacks have become more prevalent in the last 2-3 years.

Addendum: @raybeere: If the PSU is indeed a switchmode type, (they're generally lighter than transformer types is the easiest way to tell), then you should change it for the same type with an equivalent rating if you intend to.  The unregulated output from a generic transformer based PSU might damage the router, (unless the replacement specifically states it is regulated).
« Last Edit: July 15, 2009, 10:32:53 PM by 4wd »

40hz

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #20 on: July 16, 2009, 07:39:24 AM »
If your device requires 12V DC there will typically be a 7812 regulator connected to it's input power socket - it's relying on the normally unregulated voltage provided by the transformer plugpack of around 16V DC allowing it regulate correctly.

If you build the circuit as described and set its output to 12V DC and then plug that into your device, where does the internal regulator get its required voltage drop in order to regulate?

That question is addressed in the article. Look under the Selecting an Appropriate Wall Wart heading. You might miss it if you're just looking at the scematic. :)

Quote

...

Within the range of regulated supplies requiring 100 to 150 milliamperes or less, the primary concern in selecting a wall wart is to make sure that it will supply power at least 3 volts DC in excess of the desired final controlled voltage, when the circuit is running at the designed load. This "3 volts in excess" comes from the basic needs of the voltage regulator itself. The most straight-forward approach to selecting a wall wart for your project would be to select one with an amperage rating that matches your needs and a voltage rating that is 3 or 4 volts higher. Thus, if you need a 5 VDC, 100 ma. regulated supply, you might select a used "9 VDC" wall wart rated at 100 or 150 ma. If you need a 9 volt regulated supply at 70 ma., you might select a small "12 VDC" wall wart rated at 100 ma.

The selection becomes a bit more complex, if you desire a 12 volt regulated supply. One way to go is, as discussed above, to use a 14, 15 or 16 VDC wall wart rated at least as large as your design load in milliamperes...


« Last Edit: July 16, 2009, 07:41:15 AM by 40hz »

4wd

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #21 on: July 16, 2009, 08:33:32 AM »
That question is addressed in the article. Look under the Selecting an Appropriate Wall Wart heading. You might miss it if you're just looking at the scematic. :)

Guilty as charged!  :-[

I did mainly only look at the circuit, (which is just the standard linear regulator circuit), but I also noted from the article they never took into account the fact that most transformer powered equipment will have it's own internal regulator which is the point I was making.

cct.jpgA Problem for A Real Expert - the Haunted Router(s)

The top circuit shows the typical setup for a device powered by a transformer based plugpack - the regulator is situated within the device and while it gets the full voltage from the plugpack, it will happily perform it's job.  (A 12V unregulated transformer based plugpack can typically provide up to ~16V.)

The bottom circuit shows what you get when you follow the article, you have removed the internal regulators minimum voltage drop - it will no longer regulate.

Quote

...

Within the range of regulated supplies requiring 100 to 150 milliamperes or less, the primary concern in selecting a wall wart is to make sure that it will supply power at least 3 volts DC in excess of the desired final controlled voltage, when the circuit is running at the designed load. This "3 volts in excess" comes from the basic needs of the voltage regulator itself. The most straight-forward approach to selecting a wall wart for your project would be to select one with an amperage rating that matches your needs and a voltage rating that is 3 or 4 volts higher. Thus, if you need a 5 VDC, 100 ma. regulated supply, you might select a used "9 VDC" wall wart rated at 100 or 150 ma. If you need a 9 volt regulated supply at 70 ma., you might select a small "12 VDC" wall wart rated at 100 ma.

The selection becomes a bit more complex, if you desire a 12 volt regulated supply. One way to go is, as discussed above, to use a 14, 15 or 16 VDC wall wart rated at least as large as your design load in milliamperes...

All they are concerned with here is the input requirements of the external regulator they are adding, not the input requirements of the internal regulator of the device.  ie. The internal regulator could be relying on that 'excess' voltage from a transformer.

It all comes down to the construction of the device that's being powered.  Personally, I wish they'd get rid off the freakin' need for the plugpacks - I'll generally try to buy equipment that doesn't require them now, direct mains powered is so much easier.
« Last Edit: July 16, 2009, 08:55:37 AM by 4wd »

40hz

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #22 on: July 16, 2009, 10:04:16 AM »
Personally, I wish they'd get rid off the freakin' need for the plugpacks - I'll generally try to buy equipment that doesn't require them now, direct mains powered is so much easier.

+1 on that. But the decision to use external PSUs is more a matter of economics than engineering.

I don't know how it works where you are, but in the USA, all devices that plug directly into AC mains require certification from the Underwriter's Laboratory before they can be legally sold. If you power your device with a plug-type PSU - and don't have an AC line coming into your device - only the PSU needs to be certified as opposed to the entire device. So manufactureres can just stock up on pre-certified external power supplies and be done with it. Saves them a huge amount of money since getting UL approval is time consuming and expensive. Also reduces their liability in the event the PSU burns.


4wd

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Re: A Problem for A Real Expert - the Haunted Router(s)
« Reply #23 on: July 16, 2009, 07:27:56 PM »
I don't know how it works where you are, but in the USA, all devices that plug directly into AC mains require certification from the Underwriter's Laboratory before they can be legally sold. If you power your device with a plug-type PSU - and don't have an AC line coming into your device - only the PSU needs to be certified as opposed to the entire device. So manufactureres can just stock up on pre-certified external power supplies and be done with it. Saves them a huge amount of money since getting UL approval is time consuming and expensive. Also reduces their liability in the event the PSU burns.

Same here, although there have been cases where the supposedly 'certified' PSU or device is really just wearing a faked sticker.