Hi! I'm not sure if this is the correct subforum to ask this question in.

I am trying to repair a V1 TP-Link Archer VR900 router which I just picked up second hand. The power electronics seem to have failed as both chargers I've tested will make a ticking noise which is likely some sort of protection function and the device won't start. Upon disassembly it looks like at least 2 capacitors have come off the board - C3 & C5 the former of which I saw was half-attached and came off with a light touch from my screwdriver.

Not sure how this damage would occur, but I want to attempt a repair even though the router was of little expense. I like to fix things!

From a bit of research, I believe the capacitors are ceramic capacitors? They are 1mm in length. The device is rated at 12V dc up to 3.3 AMPs, and the capacitors are positioned on the other side where the dc jack power socket is, I suspect it's part of the power electronics.

C3 looked the same as C321 - but I have no idea what sort of specs these capacitors have as they're too small to have any identifiable details printed on them, can somebody help and advise what may be a suitable replacement - preferably one which would be easier to solder than these tiny 1mm cuboid capacitor. If they can't be identified what would be your best guess at a replacement capacitor which may work in this circuit?

Here's some photos:

http://imgur.com/tR6sm8R

http://imgur.com/2cT31X8

http://imgur.com/ZegTp0r

http://imgur.com/kY5IbII

Many thanks!

 

You'll have to have another go at the pictures!

 

You'll have to have another go at the pictures!

You can't see them? I've attached to this reply now

 

The solder on FB1, FB2, and FB4 look like they have got hot. I doubt that the heat was generated by those components. On the other side of the board in that corner there is a square black component. If this is a voltage regulator then it might have got hot enough to melt the solder on C3 and C5.

What numbers/letters are on that black square?
which side of the board was upwards when it was in the router?

 

The solder on FB1, FB2, and FB4 look like they have got hot. I doubt that the heat was generated by those components. On the other side of the board in that corner there is a square black component. If this is a voltage regulator then it might have got hot enough to melt the solder on C3 and C5.

What numbers/letters are on that black square?
which side of the board was upwards when it was in the router?

I've attached some more photos.

The router sits vertically, the side with the heat sink faces backwards and the dc jack & small black square are on the back in the bottom-left corner.

I did notice when device was left plugged in for a few minutes, the dc jack area on the device was warm to the touch, as was the power lead connector. Not hot, just warm.

Small black square has "SK54C GP" printed on it

Thanks for your help!

 

If the board is vertically mounted then my idea is a non-starter. If the diode (SK54C is a diode) got hot enogh to melt solder it would have fallen off the board not the capacitors

 

If the board is vertically mounted then my idea is a non-starter. If the diode (SK54C is a diode) got hot enogh to melt solder it would have fallen off the board not the capacitors

Yes I don't think it overheated, at least not in my possession. Do the rest of the surrounding components seem okay to you? Any guess on what the miniature capacitors may be rated for? I'm guessing that due to their size they would be within a limited range of possible ratings. Would it be worth trying to add a capacitor that isn't perfectly matched to the original? It's not much to me if I damage the board any further

 

Ceramic capacitors are available in that size for a wide range of capacitor values (pF to uF, only low voltage needed).

 

Ceramic capacitors are available in that size for a wide range of capacitor values (pF to uF, only low voltage needed).

Thanks again.

Is there any way at all to identify what rating I should be looking for? or a relatively good guess on what I should go for if not able to identify?

Regards

 

As a WAG, 100nF is a common value.
Does it work without them?

 

As a WAG, 100nF is a common value.
Does it work without them?

No, the router won't switch on and the power adapter connecting to it makes a ticking sound about twice a second.

It appears the size I'm looking for is an 0402 capacitor - and I would suppose anything above 12v?

All I've been able to find so far for 0402 size is 47nF and 25v

 

I don't think those capacitors would fix the ticking.

 

I don't think those capacitors would fix the ticking.

The chargers are functional (I've two here that supply enough power - both with same ticking result) and I think the ticking is some sort of protection circuitry. The router actually worked the first time I switched it on but after a few minutes it failed and here I am now..

Either way, I've nothing to lose and doing this mostly for the experience.

Managed to locate C0402C104K4RAC7411 capacitors, 16V, 100nF and 1mm long - these could be acceptable?

 

The chargers are functional (I've two here that supply enough power - both with same ticking result) and I think the ticking is some sort of protection circuitry. The router actually worked the first time I switched it on but after a few minutes it failed and here I am now..

Either way, I've nothing to lose and doing this mostly for the experience.

Managed to locate C0402C104K4RAC7411 capacitors, 16V, 100nF and 1mm long - these could be acceptable?

It's as good a guess as any other.

 

It's as good a guess as any other.

Thanks for your help