Is this a fuse? (and should I replace it...)

Thread Starter

CurlsOnKeys

Joined Jan 3, 2015
47
Hi all,

simple question. USB-connector of my MIDI-controller broke off, decided to try give it a shot and replace it with a new one.
Desoldered the old connector, soldered on the new one, but unfortunately USB-midi (and USB-power) still didn't function.

Upon further inspection, I noticed that two components appeared to be "missing" somehow. Maybe I applied to much heat during desoldering, maybe they we're never there, I don't know, anyway, they're gone. Talking about FP2 and F1 on the picture.
My guess is that these "F" things are fuses, correct?

I see them on every (yes, every) input/output pin on the CPU-board. So all four USB-pins are connected to an F (or FP) SMD. There are also regular old fashioned MIDI-connectors (5-pin-DIN), some TRS-audiojack-connectors: all pins of those connectors are attached to an F-type thing. A fuse, I guess. Is it really necessary to fuse every input/output connection? And so: should I replace those missing fuses? But what should there mA-rate be, they're not marked and I don't have the schematic? Or can I simply connect them through a simple wire and pray all goes well? :)

Thanks!

image_11.jpg
 

Thread Starter

CurlsOnKeys

Joined Jan 3, 2015
47
Look like fuse protection blocks, if there's no markings on them, jumper them out with wire.
Thanks for your help! So what's their use then? Or are they (most of the time) simply there because of regulations and design rules (as I read somewhere else?)
 

Thread Starter

CurlsOnKeys

Joined Jan 3, 2015
47
for protection to the pcb from the outside world.
So no more protection than on those 2 pins? :) Well I guess it's either that or a non-functioning device anyway, so I'll take your advice and jumper them out.

Thanks. In return I'll shout a bit harder to my tv-set to try and get The Reds to make 3 more goals :)
 

BReeves

Joined Nov 24, 2012
410
I wouldn't jump at just shorting them.. Could very well be just alternates to F2 and FP1, I would see if the two components have any pins in common and check F1 and FP2 for continuity. I'm not sure what FP1 is maybe a fuse maybe not.
 

Thread Starter

CurlsOnKeys

Joined Jan 3, 2015
47
I wouldn't jump at just shorting them.. Could very well be just alternates to F2 and FP1, I would see if the two components have any pins in common and check F1 and FP2 for continuity. I'm not sure what FP1 is maybe a fuse maybe not.
No pins in common and no continuity between fuses. 4 pins on the USB-connector, connected to four fuses. FP1 goes to ground, FP2 to C15, F2 to R3 and F1 to R2.
 

ian field

Joined Oct 27, 2012
6,539
I wouldn't jump at just shorting them.. Could very well be just alternates to F2 and FP1, I would see if the two components have any pins in common and check F1 and FP2 for continuity. I'm not sure what FP1 is maybe a fuse maybe not.
If the FP was the other way round, I'd throw a wild guess at polyfuse.
 

RichardO

Joined May 4, 2013
2,268
I am guessing that F1 is a ferrite filter for EMI suppression. Jumpering that would not do any electrical damage but your AM radio (etc.) may quite working from the added interference.

FP1 anbd FP2 are "big" devices and have "wide" traces to the connector. I am, again, guessing that they are also EMI filter ferrite. They and the traces are large because they are on the power and ground pins.

You can verify the F1 and F2 parts connect to the signal pins and that FP1 and FP2 connect to the power pins on the connector using an ohmmeter.
 
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