SMD  FUSE or RESISTOR marked as 0 (zero) .... - Page 1
Forum section: electronics / repair

author: PKTKS
author_rank: Super Contributor
timestamp: October 30, 2018, 05:55:27 pm
content: 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 fusesof some sort... or so...** and if so to point any reasonable understandable TABLE or CROSSREF guidethese crappy little components marked as zero may be causing issuesand i have found no clear directiveAny help welcomeThanks a lot.Paul

author: RoGeorge
author_rank: Super Contributor
timestamp: October 30, 2018, 05:58:01 pm
content: Zero resistors are for debug purposes, so one can de-solder them instead of cutting the PCB trace.

author: PKTKS
author_rank: Super Contributor
timestamp: October 30, 2018, 06:00:13 pm
content: Ouch the board is infested with at least 10 of themVarying sizes and locations...Are they a new JUMPER thing?or some DO INDEED SERVE other purpose ?

author: ataradov
author_rank: Super Contributor
timestamp: October 30, 2018, 06:31:04 pm
content: 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.

author: tkamiya
author_rank: Super Contributor
timestamp: October 30, 2018, 06:40:36 pm
content: 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.

author: RoGeorge
author_rank: Super Contributor
timestamp: October 30, 2018, 06:42:41 pm
content: 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.

author: PKTKS
author_rank: Super Contributor
timestamp: October 30, 2018, 06:51:42 pm
content: 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 fuseand the SMPS happily fried the board with no hesitationSo.. while investigating the cause I have doubts why with so manyof these 0 zero SMD pieces neither one tripped or fried.they just happily survived while the board cooked

author: ataradov
author_rank: Super Contributor
timestamp: October 30, 2018, 06:54:14 pm
content: 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.

author: PKTKS
author_rank: Super Contributor
timestamp: October 30, 2018, 07:02:42 pm
content: I have already removed them all..and tested them all as wellThey are all out with all the ELCO caps and some fried chipsThe board is lost... 100% lostThis is what is left of it...

author: RoGeorge
author_rank: Super Contributor
timestamp: October 30, 2018, 07:06:39 pm
content: 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).

author: PKTKS
author_rank: Super Contributor
timestamp: October 30, 2018, 07:08:09 pm
content: 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..

author: PKTKS
author_rank: Super Contributor
timestamp: October 30, 2018, 07:10:33 pm
content: 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 boardI collected them to test. With the ELCO caps.They are packaged as resistors but marked just 0 - plain zeroPaul

author: schmitt trigger
author_rank: Super Contributor
timestamp: October 30, 2018, 07:20:31 pm
content: Could you kindly show a closeup, focused photo of those zero-ohm resistors?

author: RoGeorge
author_rank: Super Contributor
timestamp: October 30, 2018, 07:22:13 pm
content: 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.

author: PKTKS
author_rank: Super Contributor
timestamp: October 30, 2018, 07:28:02 pm
content: Yes this is an Altec dock station audio systemThe SMPS is external with a DC jack in.A daughter board "glued" (the white thing) host the inputsIt fried really bad - really bad.I have already messed some of the original "0" thingsof this board but give me some time to put that on the scopeto a decent shot. May be later...I will post the 2 footprints of these "resistors" marked 0which judging by the comments they don't act as fuses of any kindI will try a scope shot of some .. already removed and testedPaul

author: PKTKS
author_rank: Super Contributor
timestamp: October 31, 2018, 01:12:19 pm
content: OK here a clear shot of some of these "resistors" removedfrom this board and also from another (hybrid dead ATX under troubleshooting)I have collected and tested them all and they are fineThey don't blow and as it seems they resisted better thanthe toasted PCB traces ...Some of them here on the shotso by the comments these things are just jumpers?Paul

author: schmitt trigger
author_rank: Super Contributor
timestamp: October 31, 2018, 03:11:26 pm
content: 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.

author: forrestc
author_rank: Unknown
timestamp: October 31, 2018, 03:18:34 pm
content: Quote from: PKTKS on October 31, 2018, 01:12:19 pmYes, 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.

author: PKTKS
author_rank: Super Contributor
timestamp: October 31, 2018, 03:28:14 pm
content: 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 wherethe traces just carbonized...So jumpers they are... That is new to me.Paul

author: schmitt trigger
author_rank: Super Contributor
timestamp: October 31, 2018, 03:49:51 pm
content: "000" !!The vendor wants to make sure you have a1%zero-ohm jumper.

author: Chris56000
author_rank: Frequent Contributor
timestamp: October 31, 2018, 03:54:29 pm
content: 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

author: ataradov
author_rank: Super Contributor
timestamp: November 02, 2018, 06:14:39 pm
content: 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/

author: PKTKS
author_rank: Super Contributor
timestamp: November 03, 2018, 06:22:10 pm
content: Sleeping on that...I was considering that VIAS just retired the jumpers - until nowI was wondering if using these components instead of VIAS is cost-effectiveA gross math of 100 of these plus solder plus pads...Any modern router would just place a VIA there integrated on the final costI was wrong JUMPERS are still alivebut I DON'T know how to find that on modern EDA suites..which by default spread VIAS everywhere...Paul

author: ataradov
author_rank: Super Contributor
timestamp: November 03, 2018, 06:24:52 pm
content: Quote from: PKTKS on November 03, 2018, 06:22:10 pmThose 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.