Dell SP2008WFPt no picture

[jetadm123]

Re: Dell SP2008WFPt no picture

Indeed, I misread your previous post.

Which one is the input pin?

Refering back to the photo in post #9, with the tab on the bottom, input pin is left, output is middle pin and ground is right pin.

[jetadm123]

Re: Dell SP2008WFPt no picture

That's also what I though.

I still get 0V on all pins.

I compared with the other regulator and that one is still working.


EDIT: Is is possible that this regulator is there for the USB hub, in which nothing is plugged right now, explaining the lack of voltage in there?

You can try tracing the input and output pins of the reg to see where they lead. It's been my experience that these voltage regs are always powered on.

[kynax]

Re: Dell SP2008WFPt no picture

You can try tracing the input and output pins of the reg to see where they lead. It's been my experience that these voltage regs are always powered on.

Did some more investigating.

See attached picture.

Point 1 has 5.27V, point 2 has 5.07V, point 3 has 0V.
Point 3 then goes to a fuse (blue box) and to a test point.
It then goes into a capacitor and into the input of the big regulator.
The output of the regulator is connected to the other side of the capacitor and to the ground.

The small box on top (with point 1, 2 and 3) is too small for me to read the text on top, but is labelled Q308 on the board.

[alexanna]

Re: Dell SP2008WFPt no picture

Did some more investigating.

See attached picture.

Point 1 has 5.27V, point 2 has 5.07V, point 3 has 0V.
Point 3 then goes to a fuse (blue box) and to a test point.
It then goes into a capacitor and into the input of the big regulator.
The output of the regulator is connected to the other side of the capacitor and to the ground.

The small box on top (with point 1, 2 and 3) is too small for me to read the text on top, but is labelled Q308 on the board.

I would like to make a suggestion.
It would be a good idea to verify you have a ground on the regulator. What voltage reading do you get with the red lead on pin 1 and the black lead on pin 3?

[kynax]

Re: Dell SP2008WFPt no picture

I would like to make a suggestion.
It would be a good idea to verify you have a ground on the regulator. What voltage reading do you get with the red lead on pin 1 and the black lead on pin 3?

Those pins are in reference to my picture above right?

I get 5.23V between pin 1 and pin 3 (the configuration you asked for) and 5.04V between pin 2 and pin 3.

[alexanna]

Re: Dell SP2008WFPt no picture

I am sorry i was referencing pins on how Jetadm 123 described them, not how you labled them

[kynax]

Re: Dell SP2008WFPt no picture

I am sorry i was referencing pins on how Jetadm 123 described them, not how you labled them

I don't get anything (0V), which doesn't suprise me since the input pin doesn't show anything when tested with the ground.

[alexanna]

Re: Dell SP2008WFPt no picture

You are seeing 0 volts on pins 1 and 3?

[kynax]

Re: Dell SP2008WFPt no picture

You are seeing 0 volts on pins 1 and 3?

Correct.

But isn't that the same test as in post #10?

[alexanna]

Re: Dell SP2008WFPt no picture

If we are talking about the same pins [the 2 outter]
i don't think you have a ground,Unless it's a switched on and off ground.

[kynax]

Re: Dell SP2008WFPt no picture

The rightmost pin is indeed connected to ground.

The leftmost has 1200 ohms of resistance with pin 3, but that might be through a charged capacitor somewhere else since it starts low and goes up in about 2 seconds.

[jetadm123]

Re: Dell SP2008WFPt no picture

FYI- the "F" and "FB" designators mean two different things: The "F" designates a fuse as mentioned earlier. "FB" designates a Ferrite Bead, which is not a fuse, but a bead of ferrite over a piece of wire.

As for Q308, it's some type of transistor. Since you can't read the part number, I'll take a WAG and using your numbering scheme for the legs and with power off, try measuring for shorts across legs 1-3, 2-3 and 1-2.

[kynax]

Re: Dell SP2008WFPt no picture

1-3 427 ohms
2-3 infinite ohms
1-2 infinite ohms

I'm pretty sure some of these combinations charge a capacitor since 1-3 will sometimes show infinite resistance right after testing another combination. Does that make sense?

[jetadm123]

Re: Dell SP2008WFPt no picture

I looked at your photo a little more closely. From your drawing you stated that the the output of the regulator is connected to one side of the capacitor and to ground. How can the output be connected to ground?

It would make more sense if the output of the reg is connected to the "+" side of the cap and the ground leg of the reg is connected to ground, but not connected to the output leg of the reg.