teeny micro-minature SMD fuses

I have a DDS tape drive. When plugged in, none of the LEDs come on.
It is supposed to do a self-test.
Next to the power socket are two rectangular things approximately 5x2x2 mm.
I assume they are fuses, because when I put a voltmeter on the tracks,
one is passing 12 V, but there is no 5 V on the other.
I have seen "nano" and "pico" PCB fuses before, but these things are
absurdly small. How could you possibly replace one? I guess it really is
a throw-away item.
I think they are no longer made, but "new old stock" is $1000.

 

[Clocky]

On 15/06/2018 8:03 PM, bruce56@topmail.co.nz wrote:

I have a DDS tape drive. When plugged in, none of the LEDs come on.
It is supposed to do a self-test.
Next to the power socket are two rectangular things approximately 5x2x2 mm.
I assume they are fuses, because when I put a voltmeter on the tracks,
one is passing 12 V, but there is no 5 V on the other.
I have seen "nano" and "pico" PCB fuses before, but these things are
absurdly small. How could you possibly replace one? I guess it really is
a throw-away item.
I think they are no longer made, but "new old stock" is $1000.

Solder a bridge and see if the thing still works. Alternatively solder a
couple of wires to the fuse ends and then to any fuse or fuse holder
that you have handy. You can use an Ammeter to see what the current draw
is and use a fuse that is rather for a couple of amps more.

 

[Computer Nerd Kev]

bruce56@topmail.co.nz wrote:

I have a DDS tape drive. When plugged in, none of the LEDs come on.
It is supposed to do a self-test.
Next to the power socket are two rectangular things approximately 5x2x2 mm.
I assume they are fuses, because when I put a voltmeter on the tracks,
one is passing 12 V, but there is no 5 V on the other.
I have seen "nano" and "pico" PCB fuses before, but these things are
absurdly small. How could you possibly replace one? I guess it really is
a throw-away item.
I think they are no longer made, but "new old stock" is $1000.

Given the position, it does sound like a fuse, or a fusible resistor.
But the markings are usually pretty vague on such components, so I
suspect that a more informed search might bring up better
replacements than the $1000 one you found. They won't be designed
to be replaced, though with a special soldering iron, or some solder
wick and some patience, it would be do-able.

I agree with Clocky though, in a DDS tape drive you should be able
to find space to put in a normal fuse and connect it via wires.
Then the question is whether there's a short elsewhere that caused
the original fuse to blow.

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[keithr0]

On 6/16/2018 1:43 AM, Clocky wrote:

On 15/06/2018 8:03 PM, bruce56@topmail.co.nz wrote:
I have a DDS tape drive. When plugged in, none of the LEDs come on.
It is supposed to do a self-test.
Next to the power socket are two rectangular things approximately
5x2x2 mm.
I assume they are fuses, because when I put a voltmeter on the tracks,
one is passing 12 V, but there is no 5 V on the other.
I have seen "nano" and "pico" PCB fuses before, but these things are
absurdly small. How could you possibly replace one? I guess it really is
a throw-away item.
I think they are no longer made, but "new old stock" is $1000.




Solder a bridge and see if the thing still works.

Yep its an excellent way to see where the smoke comes out.

Alternatively solder a
couple of wires to the fuse ends and then to any fuse or fuse holder
that you have handy. You can use an Ammeter to see what the current draw
is and use a fuse that is rather for a couple of amps more.

Best to start with a low current fast blow fuse, otherwise you may just
as well solder in a short.

 

[Colin Horsley]

On 15/06/2018 22:03, bruce56@topmail.co.nz wrote:

I have a DDS tape drive. When plugged in, none of the LEDs come on.
It is supposed to do a self-test.
Next to the power socket are two rectangular things approximately 5x2x2 mm.
I assume they are fuses, because when I put a voltmeter on the tracks,
one is passing 12 V, but there is no 5 V on the other.
I have seen "nano" and "pico" PCB fuses before, but these things are
absurdly small. How could you possibly replace one? I guess it really is
a throw-away item.
I think they are no longer made, but "new old stock" is $1000.


Which DDS drive? Model???

Col

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On Saturday, June 16, 2018 at 9:01:19 AM UTC+8, Computer Nerd Kev wrote:

Given the position, it does sound like a fuse, or a fusible resistor.
But the markings are usually pretty vague on such components, so I
suspect that a more informed search might bring up better
replacements than the $1000 one you found.

I got a used drive for $100, actually an old server that happened to have
a drive in it. So got a SCSI cable as well, but the rest of the server is
pretty much junk.