My ASUS RT-N66U Router Died. Well, Sort of...

[Deleted member 191766]

I got a little hung up on wanting to understand how such switches latch and am happy to have that out of the way.

 

[Bill_Bright]

Looks like it is the middle (chevron) catch that breaks on failure

Could be, but without seeing a damaged part to compare it with, that is is just speculation. The problem could be the point where that chevron catch latches on to. It could be rounded off due to wear or misaligned due to a design or manufacturing defect.

I really don't see this being caused by heat - unless the router was faulty and essentially on fire! While there are some plastics with relatively low melting points, it would make no sense to use those plastics in electronics - especially one where the part is used in an application where strength and rigidity is required - like a major component inside a push button switch.

If you look at the melting point of common plastics, most are well above 100°C. If you look at the spec sheet for the operating temperature for that ASUS router, it is up to 40°C. If you look at the data sheet for this switch, the operating range is up to 85°C. 60°C will leave 2nd degree burns on your skin. Temperatures above 72°C will destroy your skin on contact. Then look at the materials section and note the actuator is made of Acetal. Acetal has a melting point of 162°C! That's 323.6°F and water boils at 100°C or 212°F.

That Farnell switch uses PA 66 (polyamide 66) for the actuator. As seen here (look at datasheet), PA 66 has a melting point of 258°C and a long term service temperature of 100°C. Long term service temperature is "the maximum acceptable temperature above which mechanical properties (tensile strength, impact strength) or electrical properties (dielectric strength, linked to insulation properties) of a plastic part are significantly degrading, over the reasonable life time of the tested product. "

Conclusion - that switch would have to be operating in temperatures over 100°C (212°F) for extended periods (170°C/338°F short term) before it's tensile and impact strength degraded. Therefore, I refuse to believe failure of these switches is caused by heat.

 

[Deleted member 191766]

Here is a damaged part (from a picture I posted earlier in this thread); I didn't take the picture but the chevron looks missing.

Concerning heat, I recall hanging cables in an underground station that were sagging and was told that over the years they had been stretching, I think the same may be true of plastics far below melting temperature (they talk about the plastic region for metals).

If one touches the front of the unit it is a good bit above body temperature.

Remember that one theory was that the spring was too strong; that chevron is quite small. We are not talking melting but rather softening of the plastic.

 

[Bill_Bright]

Too small and blurry for my eyes.

Concerning heat, I recall hanging cables in an underground station that were sagging and was told that over the years they had been stretching, I think the same may be true of plastics far below melting temperature (they talk about the plastic region for metals).

That has nothing to do with the price of rice in China in the summertime - or with these switches. Hung cable stretches due to the effects of gravity and the weight of the cable. The plastics in these tiny switches are not impacted in that way.

Lets keep it real.

If one touches the front of the unit it is a good bit above body temperature.

So what? For one, "a good bit" means nothing in a technical discussion. For another, if you (or your skin) can tolerate the heat and not be damaged when touching something "a good bit" above body temperature, that in no way suggests the plastics inside are melting or even becoming soft, malformed or disfigured.

 

[Deleted member 191766]

Hung cable stretches due to the effects of gravity and the weight of the cable. The plastics in these tiny switches are not impacted in that way.

Lets keep it real.

Seriously? that chevron is holding back the spring 24/7

 

[Bill_Bright]

Seriously? that chevron is holding back the spring 24/7

You mean exactly like it is supposed to do? Like the millions of switches of that type used in millions of devices do everyday, day in and day out, year after year after year with no problems?

Come on! Find one of those specific ASUS routers with one of those specific failed switches, expose the innards of the switch and THEN we can talk specifics. Until then, you are just guessing, hypothesizing, speculating and making conjectures based on insufficient data - not even anecdotal evidence!

I must have a dozen or more of those type switches in devices here (including my own router and 4 Ethernet switches) and none have failed in that manner (or any other manner for that matter). Does that prove I am right and you are wrong? NO!

"IF" those switches are failing because the chevron latch on those plastic actuators cannot support the strength of the spring over long term use, then obviously, there is either a manufacturing defect or a design flaw in the construction of that specific part number. A design flaw would be the engineers selected the wrong spring, or they selected the wrong type plastic, or they failed to make that chevron latch big and strong enough - that is, human error! Not a limitation with plastics in general as you seem to be suggesting.

"IF" what you keep trying to suggest where true, then every similar push button switch in every router, every modem, every device ever made would have failed or will soon fail in the same way - that is, that little chevron latch wore out. And that is simply nonsense!

You don't know the manufacturer of the switches used in those ASUS routers.
You don't know the part number of the switches used in those ASUS routers.
You don't know how those switches used in those ASUS routers failed.

EVERYTHING you have posed here are simply guesses and suppositions. Yes, you might be right. But you could just as easily be wrong.

 

[Deleted member 191766]

I sent a picture of a failed switch. Everything I have posed here are simple guesses? The pictures included?

Sure I could be wrong. I tried the best I could in the circumstances; replacing the switch while at the same time trying to avoid doing so with the same switch.

"not even anecdotal evidence"; all those Web pages of failures do not count?

I just don't understand the aggression; I thought we were both trying to figure this out. Work together.

Concerning

"then obviously, there is either a manufacturing defect or a design flaw in the construction of that specific part number "​

you forgot that the unit actually draws more DC current than the switch is speced for, so that is a third option.

Did I suggest they used the wrong plastic, or that they used the plastic wrongly? or neither; maybe they started using a stronger spring.
You earlier seem convinced that I was claiming color represented specs and proceeded to attack that (a straw man argument). Color was a
way to try and locate another manufacturer without actually knowing the original manufacturer.

Sure "IF" I had known all the part numbers, I could have known more, but perhaps still not enough to know why switches were failing;
and I DON'T think the chevron latch wore out... things failed just sitting there, so yes, that would be nonsense.

I though we were making progress as to how (perhaps/maybe) the switch might be failing. For me it was a fun project with a tangible outcome.
I learned a lot (how a latching switch works) and modified my unit even if it perhaps didn't really need any repair. You were part of that learning
process by questioning conjectures. One normally thinks of a switch as a simple device, but here I learned that perhaps even the strength of the
return spring is important. For that I thank you, but it would have been nice had it been a little less caustic. Then again, perhaps it was called for.

 

[Bill_Bright]

I sent a picture of a failed switch. Everything I have posed here are simple guesses? The pictures included?

"A" failed switch?

Why don't you get this? Is that picture a picture of the exact same switch used in these routers? YOU DON'T KNOW!!!! You are simply guessing then assuming what you see in your switch is exactly what is happening in those other switches.

I just don't understand the aggression; I thought we were both trying to figure this out. Work together.

It is not aggression. It is frustration. You are convinced you know exactly what is wrong when YOU DON'T KNOW the maker of the switch or the part number of the switch, or even how the actual failed switch failed. You are guessing at every point along the way.

First you found a picture of a switch that "look like the switch". It was made by C & K. Note it is "black".
Then you decided the failing switches were "blue" and you insisted blue had to represent some value. So getting a different color would solve all your worries. And you were claiming color represented specs. See your own post number #19 where YOU said,

So, yes, the color has everything to do with this

Then you guessed the chevron "breaks" upon failure - guessing it is because the spring is too strong. Now you are convinced it didn't wear out.

Concerning
"then obviously, there is either a manufacturing defect or a design flaw in the construction of that specific part number "you forgot that the unit actually draws more DC current than the switch is speced for, so that is a third option.

Come on! That is more nonsense. If the router draws more power than the switch is designed for, then that is a design flaw! The engineers screwed up and picked the wrong part. Human error! And in any case, that would NOT cause the switch to break in this manner. Instead, it would be a safety issues likely to result in a recall.

So again, you just keep guessing, hypothesizing, speculating and making conjectures based on insufficient data! And until we learn the specific switch by brand and part number, guesses is all it will be.

I see no reason to beat this dead horse any longer.

 

[Deleted member 191766]

OK, I'm done.