SMD FUSE or RESISTOR marked as 0 (zero) ....

[PKTKS]

I have some boards with a plethora of  different  SMD RESISTORS
(i will call them resistors)  which vary even in size (footprints)

As SMD fuses nowadays are widely  different from the "regular" 
wire glass and  ceramic  fuses...  i am confused  ...

--  Does anyone can tell

** IF ALL THESE MARKED "0" (zero) smd resistors will behave like fuses
of some sort...  or so...

** and if so  to point any  reasonable understandable TABLE or CROSSREF guide

these crappy little  components marked as zero may be causing issues
and i have found no clear directive 

Any help welcome
Thanks a lot.
Paul

[RoGeorge]

Zero resistors are for debug purposes, so one can de-solder them instead of cutting the PCB trace.

[PKTKS]

Ouch  the board is infested with at least 10 of them

Varying sizes and locations...

Are they  a new JUMPER thing? 
or some DO INDEED SERVE other purpose ?

[ataradov]

Sometimes people use them as jumpers, which seems to be the case here if they are all over the place.

Picture of the board may help. If they all have traces under them, then they are most likely just jumpers. This is a very common occurrence on single-sided boards.

[tkamiya]

Also, those zero chips make PCB customizable and multi-purpose.  That way, manufacturers can make fewer PCB variety to cover wider product ranges. 

I don't see them as a "jumper" which were often signs of poorly designed PCB. 

[RoGeorge]

They can be also used as configuration jumpers, sometimes in a cheap single side PCB as a jumper over another trace, etc. The idea is zero resistors are not SMD fuses.

[PKTKS]

Thanks folks..

The board fried ...  I am in a process of de-soldering ..
But  at this point I consider lost case.

My guess is that an MLCC bad placed near connectors just cracked ..

The crack  as it seems short circuit not enough to trip any fuse
and the SMPS happily  fried the board with no hesitation

So.. while investigating the cause I have doubts why with so many
of these 0 zero SMD pieces  neither one tripped or fried.

they just happily  survived while the board cooked

[ataradov]

You have asked about 0 Ohm resistors, yet your pictures show none.

They are not fuses anyway, so there is no expectation from them to protect anything.

[PKTKS]

I have already removed them all..

and tested them all as well

They are all out with all the ELCO caps and some fried chips

The board is lost... 100% lost

This is what is left  of it...

[RoGeorge]

I think that's a ferrite bed (in the first picture you attached in this thread). A zero ohm resistor is usually flat, and marked with 0. A ferrite bad is usually an unmarked rectangular parallelepiped.

Ferrite beds are used to suppress high frequency parasitic and spikes on the power traces (RF choke).

[PKTKS]

Actually  the thing is that IF NO FUSE tripped ...

And no protection kicked in..  this thing smoked at will..

FIRE HAZARD... w/so many of these "0" pieces..

They did not remembered to put a single fuse on the board... 

FIRE HAZARD. Old school fuses would trip just fine..

[PKTKS]

No no.. they are really 0 zero thing jumpers.. (saved them after testing)

The picture is the fried part.. these 0 folks were spread all over the board
I collected them to test. With the ELCO caps.

They are packaged as resistors but marked just 0 - plain zero
Paul

[schmitt trigger]

Could you kindly show a closeup, focused photo of those zero-ohm resistors?

[RoGeorge]

If that board is from an audio system (judging by the Altec Lansing manufacturer), than most probably the fuse is a Thermal Fuse inside the AC transformer (usually placed under the plastic wrap of the transformer's secondary winding). Placing the thermal fuse inside the AC transformer will protect all the secondary circuits, including the wires, the power rectifier and all the boards.

[PKTKS]

Yes this is an Altec dock station audio system
The SMPS is external  with a DC jack in.

A daughter board "glued" (the white thing) host the inputs
It fried  really bad - really bad.

I have already messed some of the original  "0" things
of this board but give me some time to put that on the scope
to a decent shot.  May be later...

I will post the 2 footprints of these "resistors"  marked 0
which judging by the comments they don't act as fuses of any kind

I will try  a scope shot of some .. already removed and tested

Paul

[PKTKS]

OK here a clear shot  of some of these "resistors"  removed
from this board and also from another (hybrid dead ATX under troubleshooting)

I have collected and tested them all and they are fine

They don't blow and as it seems they resisted better than
the toasted PCB traces ...

Some of them here on the shot

so by the comments  these things are just jumpers?

Paul

[schmitt trigger]

Yes, most are only jumpers. Weird that they have different sizes, though.

The blue component has additional stuff written on it, but the image is blurry and can't read it.

[forrestc]

so by the comments  this things are just jumpers?

Yes, they're all just zero ohm resistors, aka jumpers.

It's not uncommon to use those on boards for various reasons:

1) Sometimes you don't know if you're going to need a series resistor or not at board design time, so you just put the pads in place, and if you don't need a series resistor, you just populate it with a zero ohm resistor.

2) Sometimes you produce several variations of the same designs which use the same board.   In some cases, to do this, you need a soldered-in jumper.   So these get used.

And so on.

[PKTKS]

Thanks folks... so jumpers they are...

The "blue" actually green/cyan  is just   "000"

I was kinda hoping that they "could"  act like fuses...

They did not. They even survived high current where
the traces just carbonized...

So jumpers they are... That is new to me.

Paul

[schmitt trigger]

"000" !!
The vendor wants to make sure you have a 1% zero-ohm jumper. 

[Chris56000]

Hi!

Just to let the OP know so he's aware of this, datasheets often DO give a maximum current rating of a zero–ohm jumper, but this is purely to avoid excessive temperature rise at their end–terminations and over their bodies as a whole, in order to prevent damage to the pcb they're used on!

There are also thro' hole zero ohm links, which have a beige body and a single central black band coding them as zero, again they're intended as useful crossover devices on single–sided layouts – don't forget "pick–and–place" machines can't handle little pieces of wire!

The idea of using a very low or very high ohmic value component as a "dummy" is a very old one that predates surface–mount construction by many decades, black–and–white TV sets used to have things that look like carbon–composition resistors coded with four black rings – this indicated a "dummy" component that could be used as a former for small peaking or correction chokes in video or I.F. circuits, for instance!

Chris Williams

[ataradov]

This thread just came up and it shows perfect use for large 0 Ohm resistors as jumpers on cheaper boards: https://www.eevblog.com/forum/beginners/searching-for-parts/

[PKTKS]

Sleeping on that... 

I was considering that VIAS just retired the jumpers - until now

I was wondering if using these components instead of VIAS is cost-effective

A gross math of 100 of these plus solder plus pads...
Any  modern router would just place a VIA there integrated on the final cost

I was wrong JUMPERS are still alive
but I DON'T know how to find that on modern EDA suites..

which by default spread VIAS everywhere...

Paul

[ataradov]

I was wrong JUMPERS are still alive but I DON'T know how to fin that on modern EDA suites..

Those things are routed by hand. It is a one time effort for something you will produce millions of. It is totally worth it.

And yes, 0 Ohm resistors as jumpers are compatible with modern SMT process and are cost effective/. Especially when used on a single sided phenolic board.