Blown Fuses

[Sean Nelson]

Surface mount fuses, OK that makes sense. In the OP I was imagining more traditional user-replaceable fuses, but SMT fuses would be just like any other discrete component wave-soldered to a circuit board. Here's a picture of one:



I checked my disassembled Sony DSC-P1 camera and the power board does have what looks to be a few of these on it. They're tiny, only a 2 or 3 mm long each.

But although these are fuses, they're not replaceable. If one of these were to blow it wouldn't be any different than if one of the integrated circuits died - it would mean replacing the whole circuit board. The economics just aren't there for replacing the discrete components on these boards, even leaving aside the difficulty in manually desoldering and reinstalling such tiny objects without damaging the adjacent ones.

 

[Don Franco]

Actually, it isn't as hard as you might think. I have done it quite a bit. All it takes is the proper tools, a steady hand and (unfortunately probably because of doing it for a while) a lighted magnifier.

The correct "re-work" tools are pretty pricey, but I have a high-end soldering station, a self-contained vacuum de-soldering tool and also a propane powered iron that I use in my business (marine electronics) that makes it possible. The propane iron has, in addition to a variety of solder tips, a hot air tip. Hot air is what the proper re-work tools use to solder and de-solder multi-pin integrated circuits.

The biggest issue is keeping them in the proper position for soldering - I use either a very small drop of hot-melt glue or super glue.

 

[Sean Nelson]

Actually, it isn't as hard as you might think. I have done it quite
a bit. All it takes is the proper tools, a steady hand and
(unfortunately probably because of doing it for a while) a lighted
magnifier.

I'm impressed. The proper tools would help, of course, but I'm not even sure my hand would be steady enough to get a grip on some of those components.

Just out of curiousity, have you had to replace SMT fuses? I'm wondering what in your experience would have caused them to blow (understanding of course that marine electronics and digital cameras are related only by the fact that they both contain electronics...)

 

[Don Franco]

Actually, it isn't as hard as you might think. I have done it quite
a bit. All it takes is the proper tools, a steady hand and
(unfortunately probably because of doing it for a while) a lighted
magnifier.

I'm impressed. The proper tools would help, of course, but I'm
not even sure my hand would be steady enough to get a grip on some
of those components.

Just out of curiousity, have you had to replace SMT fuses? I'm
wondering what in your experience would have caused them to blow
(understanding of course that marine electronics and digital
cameras are related only by the fact that they both contain
electronics...)

Fuses do sometimes - but rarely just blow for no apparent reason. Most likely there is a fault somewhere and it is indeed preventing things from going up in smoke/further damage.

I have not replaced SMT fuses - but I have installed SMT diodes, resistors and capacitors. There are radio oriented kits out that act as training for such processes as it is getting harder and harder to find componets with wire leads for conventional thru-board construction by hobbyist. Several devices that I sell have been discontinued and replaced because of that issue as well as new environmental issues surrounding lead that went into effect in the last 1 - 2 years. A lot of manufacturers had great dificulty in complying as there were and are issue with new solder "formulations". I think that in a year or two we will see widespread failure of some devices that were developed over the period leading up to the mandates and for a period after that will have no fix other then complete replacement. The change over was not without problems. Solder is not a conductive "glue". When you sloder a connection, you form a new alloy. The recent changes result in different alloys that were unprooven and have problems in the long term.

 

[Sean Nelson]

Very interesting perspective, thanks!