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Centris 610 resistor fell off
Posted by: Mike Richardson on 2009-05-01 22:00:17
Got a Centris 610 with bad video - lines/degradation everywhere, pulled VRAM no help. Caps showing significant leakage.

Cleaned the board using 99% alcohol and a gentle brush.

Resistor C197 on the bottom side of the board still managed to fall off. It was probably loose to begin with though.

Can I just bridge the two pads, assuming if there's anything left to bridge?
Posted by: porter on 2009-05-01 22:13:17
Can I just bridge the two pads, assuming if there's anything left to bridge?
Presumably the resistor was there for a reason? Companies rarely splash out on a $0.0001 component for nothing.
Posted by: Mike Richardson on 2009-05-01 22:19:39
Can I just bridge the two pads, assuming if there's anything left to bridge?
Presumably the resistor was there for a reason? Companies rarely splash out on a $0.0001 component for nothing.
There's usually a reason, but sometimes it's not integral to the operation of the computer, and it may operate suitably without it.

I don't think it matters. It looks like the resistor rotted off or something. It took out the pads and at least one trace. This is probably a junk board.

I'll let it dry a few days and test it.
Posted by: Unknown_K on 2009-05-02 01:12:25
I would not bridge it (short) if I was you. leave it as is for now and see if the unit functions. Cxxx means capacitor no resistor and shorting out where it used to be will bridge something you do not want to bridge.
Posted by: Mike Richardson on 2009-05-02 04:11:50
I would not bridge it (short) if I was you. leave it as is for now and see if the unit functions. Cxxx means capacitor no resistor and shorting out where it used to be will bridge something you do not want to bridge.
It says Cxxx but it looks awfully like a resistor - extremely small. On the other side is a capacitor though.
Posted by: ~tl on 2009-05-02 06:16:37
I would not bridge it (short) if I was you. leave it as is for now and see if the unit functions. Cxxx means capacitor no resistor and shorting out where it used to be will bridge something you do not want to bridge.
It says Cxxx but it looks awfully like a resistor - extremely small. On the other side is a capacitor though.
SMT resistors and capacitors look virtually identical and often don't have markings on them (capacitors especially). If it has a Cxxx code on the silkscreen then it's fairly safe to assume that it's a capacitor...
Posted by: Mike Richardson on 2009-05-02 06:20:37
I would not bridge it (short) if I was you. leave it as is for now and see if the unit functions. Cxxx means capacitor no resistor and shorting out where it used to be will bridge something you do not want to bridge.
It says Cxxx but it looks awfully like a resistor - extremely small. On the other side is a capacitor though.
SMT resistors and capacitors look virtually identical and often don't have markings on them (capacitors especially). If it has a Cxxx code on the silkscreen then it's fairly safe to assume that it's a capacitor...
Then maybe it is, I don't know. I'm not an electrician.
Posted by: Apostrophe on 2009-05-10 06:28:29
I remember opening my Centris 610, back when I was testing different hard drives out on it. One thing I would always notice is like you said, it's really hard to tell which components are which. This Centris 610 has been in my family my whole life (in fact, it's just as old as me), and the logic board is in awesome condition. But I can't ever tell which ones are the capacitors. I saw several silvery cylindrical 'nubs' on the board, and I always assumed those must be capacitors--but they're not at all like the ones in a Compact Mac, or...well, any other computer I've opened.

And now you guys are saying that the capacitors look like resistors--does anyone know if there's a particular reason why the components are so confusing? 😛

-Apostrophe
Posted by: Flash! on 2009-05-11 00:20:42
does anyone know if there's a particular reason why the components are so confusing?
Those really really small components are made to a standard size/package so that they can be placed on the board by a robotic arm during manufacture. That's why they all look the same.

If you happen to know the size (ohms) of your missing resistor (or capacitor..... as the case may be) then you can always solder on the "smallest big one" you can find (1/4 watt or something). Physical size does not matter in this case.
Posted by: Dennis Nedry on 2009-05-26 08:05:49
This is absolutely a capacitor and not a resistor. It's probably not ever a good idea to short-circuit a missing component unless it's a fuse. Even then, it's not a very good idea.

Capacitors come in all different shapes and sizes. Have you seen the tantalum caps that we've used to replace the leaking cylinder-shaped electrolytic caps on these old Macs? They're yellow/orange and rectangular in shape and don't have specific polarity. Some look like round discs, some are green, yellow, black, blue, etc. Some are HUGE, some are extremely small.

Inductors also come in lots of different forms.
Posted by: Dennis Nedry on 2009-05-26 08:12:42
Tiny SMD/SMT resistors have a tendency of being black and caps tend to be brown/yellow. That's a pretty loose tendency, though. You really need to refer to the number printed on the board, R means resistor and C means capacitor.

Here are some weird capacitors:
Posted by: Flash! on 2009-05-26 22:19:20
It still stands to say that you can replace the part with a physically bigger equivilent - just as long as the electrical specification is correct.
Posted by: Dennis Nedry on 2009-05-27 08:16:01
It still stands to say that you can replace the part with a physically bigger equivilent - just as long as the electrical specification is correct.
Absolutely true. All you need is to find the value of the original capacitor. This may be desirable because of your lifted trace; you can connect the leads of an ordinary capacitor to some other easier-to-access spots on the board.
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