bubblegumhater said:
I'm having a similar problem.
I purchased a bubblebum portable hs usb 2.0 dirve. I plugged it into one of
the two usb ports that I have on my Dell Inspiron 1150. It worked fine for a
few days. Then, one day I turned on my laptop and got the "Power Surge"
message. A window popped up asking me if I wanted to continue or cancel. If I
wanted to continue choose OK to cancel choose Cancel. Ok would let me keep
working, Cancel would shut down my entire computer.
I chose OK and about 60 seconds later my monitor went black. I hooked the
laptop up to an external monitor and all is well but the laptop monitor is
still black.
You can see a very faint image on the laptop monitor of what I see on the
external monitor.
When I turn my computer on, I see the windows WP logo, the startup screen
and about 5 seconds later my monitor shuts down again.
Obviously my monitor works, but it keeps shutting itself off.
How do I fix this problem?????
SimpleTech (the bubblegum manufacturer) says it is a Dell problem but I'm
not buying that since I know that my monitor still works. GeekSquad says they
will charge me $500 and the guy was nice enough to tell me it was not worth
it. But he did not share how to fix it or where to find help on the web.
I talked to ST again today and they said that I should have plugged both
ends of the provided USB cord into my computer. I told them that the
instruction manual did not say to do that or even suggest doing that. It does
not come with a DC plug. I'm afraid to plug the thing back in out of fear
that it will fry my entire laptop.
Please help.
A USB cable with two connectors on one end, is for cases where the
device consumption is expected to break the rules for USB. By plugging
both connectors in, the idea is that the device can draw some extra
current.
A USB port is normally limited to 500mA. On a desktop board, this can be
limited by a resettable fuse (called a Polyfuse). One Polyfuse powers the
two ports in a stack, and the Polyfuse is usually set to a current higher
than 1 amp (as it is supplying two USB devices of max 500mA each).
In the case of a laptop, they may decide to use a "USB policeman", which
might take the form of an 8 pin chip. It measures the current with perhaps
more precision than a fuse, and one of the signals on the chip might be
an "OC#" signal. If more than 500mA is drawn, the chip opens the circuit,
OC# is asserted, and the laptop is protected from the excessive load.
The OC# is read by software, and "Power surge" is reported. In your
case, the report of "Power surge", will occur within the first few
seconds the USB 2.5" hard drive is connected, as the motor in the
drive needs current to spin up the spindle. If both USB are connected,
there is a better chance that the "policeman" will not be upset.
Now, no where in either description, is there room to damage other
subsystems. In terms of loading, the designers know how much +5V can
be drawn, and can accommodate that number in their design.
The light in your laptop, is a backlight, taking the form of a CCFL
(cold cathode fluorescent lamp) and a small circuit called an inverter.
The inverter converts +12V (or battery voltage, whatever that happens
to be), into 1000VAC at a high frequency. The high voltage is what makes
the CCFL tube glow and light the screen.
The inverter has a control signal. It controls the light level. When the
laptop runs on battery, the control signal may say "reduce intensity a
bit, since we need to save power". That is a form of power management.
The CCFL puts out less light, and the battery lasts longer.
The fact that you can see the Windows logo, means the backlight is running
normally, at least for a moment. When the backlight becomes really
dim, the question is, why ?
The inverter can be defective. A number of inverters display symptoms, where
after a couple seconds, they switch off their output. Now, that didn't happen
in your case, because you claim to be able to see a dimly lit image on your
laptop screen. So perhaps the signal that controls the light level, is
way off for some reason.
There really shouldn't be an interaction between the 5V used for USB
ports, and the 12V used for the backlight. And since I haven't managed to
find any "reference" laptop schematic diagrams, it isn't possible for me
to provide a hypothesis. If your inverter was "broken", then we could
discuss replacing it. But as long as the screen is capable of putting out
some amount of light, then it isn't clear that the inverter is broken.
(You could spend $100 to fix it, and not end up with a brighter screen.)
If the screen lit up for two seconds, and then was completely
extinguished, I'd say "replace the inverter", located somewhere behind or
near the LCD display. But if there is some light output, implying the
CCFL is still lighting up, then something else I don't understand, could
be broken (or mis-programmed).
Place the laptop in a completely dark room, wait for the Windows logo
to appear (which should be lighting up the room). Then wait. Is the
dim screen throwing out light ? Or is it completely dark ?
Paul
