ID surface mount capacitor?

[kalalau73]

A surface mount capacitor got knocked off my favorite 486 motherboard. I
want to try to fix it, if possible. I would rather not throw away the board
cause I like 486s. I've searched on at least 100 old boards to find one of
these chips. A few times I've found chips with similar markings, but
different size and numbers.

The broken component is a tiny grey-black rectangle about 3/16 x 1/8 x 1/16
inch with one lead on each end. One end of the of the chip has a white line
printed along it ( I assume that this signals the + end of the chip
corresponding to that marking on the motherboard). The chip has the
following markings:

10 - 25
F1 2

The 2 has a circle around it. The chip is labeled on the motherboard as
TC2 (One of four identical ). It is right next to the AT power connector.
With the chip missing off the board, the board is totally dead.

I finally found a similar chip on an old modem, the same size, but it has D3
in place of F1 (all other markings are the same).

My questions: What kind of chip is it? Is there a source to replace it? Is
there a discrete component I can substitute? Can I substitute the D3 chip?

There are some other TCx components on the board that look similar but are
tan-orange color with brown printing that says 10u 16 (could be 10 micro
farad capacitors?). There are some smaller BCx, Cx and Rx components also.
Could be 3-4 different types of capacitors: TCx (two colors), BCx, Cx ??

Thank you, I would appreciate any help.

 

[Michael A. Covington]

How confident are you that it's a capacitor? It's unlikely for a board to
go totally dead with a capacitor removed, so consider the possibility that
maybe it's a fuse. (I have no idea how to identify surface mount
components; I'm just guessing its function.)

You say it's right next to the power connector. Can you determine what it's
connected to? Is it in the path of the incoming power, the way a fuse would
be? Or is it across + and ground, the way a capacitor would be?

If it seems to be a capacitor, I would try substituting a 25-microfarad
12-volt (or higher voltage) discrete capacitor. If you can't tell which end
is positive, use a voltmeter on the place where it's going to be connected,
to see which way the voltage is applied to it.

If it seems to be a fuse, I would try perhaps a 1-amp or 2-amp discrete
fuse. But I'd make some effort to identify its function in the circuit
first.

 

[Tim Wescott]

A surface mount capacitor got knocked off my favorite 486 motherboard. I
want to try to fix it, if possible. I would rather not throw away the board
cause I like 486s. I've searched on at least 100 old boards to find one of
these chips. A few times I've found chips with similar markings, but
different size and numbers.

The broken component is a tiny grey-black rectangle about 3/16 x 1/8 x 1/16
inch with one lead on each end. One end of the of the chip has a white line
printed along it ( I assume that this signals the + end of the chip
corresponding to that marking on the motherboard). The chip has the
following markings:

10 - 25
F1 2

The 2 has a circle around it. The chip is labeled on the motherboard as
TC2 (One of four identical ). It is right next to the AT power connector.
With the chip missing off the board, the board is totally dead.

I finally found a similar chip on an old modem, the same size, but it has D3
in place of F1 (all other markings are the same).

My questions: What kind of chip is it? Is there a source to replace it? Is
there a discrete component I can substitute? Can I substitute the D3 chip?

There are some other TCx components on the board that look similar but are
tan-orange color with brown printing that says 10u 16 (could be 10 micro
farad capacitors?). There are some smaller BCx, Cx and Rx components also.
Could be 3-4 different types of capacitors: TCx (two colors), BCx, Cx ??

Thank you, I would appreciate any help.

It sounds like a tantalum capacitor, 10uF at 25V. The F1/D3 are
probably date or manufacturer's codes, and shouldn't make any
difference. I wouldn't do anything with a used SMT part but toss it
out; but if you aren't in the business then you may want to go ahead and
use the one off the modem.

PS: a 3/16 by anything surface mount part is huge, not "tiny" :->

 

[kalalau73]

Thanks for your info, I figured it out just when you posted. I think the 2
in a circle means Vishay Sprague (?) and the tan TCx are made by Kemet. I'm
not in the industry, I just find it interesting to try to figure out as many
chips on the motherboards as possible. I will try to remove and resolder
the modem chips, but my soldering is very rudimentary. I will try not to
heat up the capacitors too much.

 

[[email protected]]

Thanks for your info, I figured it out just when you posted. I think the 2
in a circle means Vishay Sprague (?) and the tan TCx are made by Kemet. I'm
not in the industry, I just find it interesting to try to figure out as many
chips on the motherboards as possible. I will try to remove and resolder
the modem chips, but my soldering is very rudimentary. I will try not to
heat up the capacitors too much.

Keep in mind that the cap does not have to be a surface mounted one.
Often a pigtailed component can be attached to a nearby point that is
electrically the same. Trace the printed wiring going to the point at
which the SMD was attached and look for a through hole component (i.e.
resistor) and tack the cap to it. It is much easier soldering to it
than it is to a SMD pad.

 

[Tim Wescott]

Keep in mind that the cap does not have to be a surface mounted one.
Often a pigtailed component can be attached to a nearby point that is
electrically the same. Trace the printed wiring going to the point at
which the SMD was attached and look for a through hole component (i.e.
resistor) and tack the cap to it. It is much easier soldering to it
than it is to a SMD pad.

You can often form the leads to hit the pads where the old cap went, as
well (I should have though of that; I've done it often enough).