Compaq Presario C700 No Video at All

[Paul678]

Ok, I've got this unit, and it doesn't have a
hard drive yet. But I know enough to realize
I should still see the BIOS boot-up sequence on
screen, and it should show me the "no bootable
drive" message.

But there is nothing. Even when I replaced the LCD
screen with a cracked spare I had laying around. I
reseated all the video and inverter connections,
and still nothing, even when I tried booting with
a Linux live CD.

Then I put an external display on the VGA output,
and still nothing, so I'm guessing the video
chip is bad on this motherboard?

Any ideas how to fix this?

[vinceroger69]

Re: Compaq Presario C700 No Video at All

i seem to remember these have a onboard graphics chip maybe worth a reflow of the chip?

[Paul678]

Re: Compaq Presario C700 No Video at All

i seem to remember these have a onboard graphics chip maybe worth a reflow of the chip?

I tried searching for a video card for this laptop on
Ebay, and nothing. I believe the video is built
into the motherboard.

Here are some pics of the same type board:

http://www.ebay.com/itm/COMPAQ-PRESA...item256dc1687c

[vinceroger69]

Re: Compaq Presario C700 No Video at All

yes looks like the one to the right of the cpu in the pic imo maybe try reflowing it if not may need re balling

[Paul678]

Re: Compaq Presario C700 No Video at All

yes looks like the one to the right of the cpu in the pic imo maybe try reflowing it if not may need re balling

Well, here's something else I didn't mention:

You know how the copper heatsink sucks heat
from both this graphics chip, and the main CPU?

Well, for some reason, the graphics chip is NOT
TOUCHING the heatsink pad. I can tell, because
when I push down on the pad, I can feel it give
about 2 millimeters or so, so I know there is
an air space between the top of the chip, and the
heatsink. Not sure how this happened, it could
have been some warpage of the PCB, but at any
rate, the graphics chip could have over-heated, and
failed.

When you say reflowing, I imagine with a hot-air
station, which I don't have.......

Not sure if it would even be worth a try, but I might
ask a friend if he has one......

[selldoor]

Re: Compaq Presario C700 No Video at All

Did it have a pad instead of thermal paste that has come off?
Perhaps try a copper shim- duel effect of moving heat and a bit of pressure onto the chip

[Paul678]

Re: Compaq Presario C700 No Video at All

Well, I was watching this xBox 360 video:

http://www.youtube.com/watch?v=1lRdAFyvrX4

So I'm sure it would be a similar procedure in my case,
but I've never done this before, and again, I don't have a
heat gun, or hot-air station.

How do you keep the caps on the other side of the
board from falling off? Is the heat dissipated by the
PCB enough so that you don't have to worry about
that?

Is there a way to test for shorts on the graphics chip with
only a DMM? Just to make it's shorted or blown out?

And if it's blown out, then I don't want to just re-flow the
solder.....I'll want to replace it with a new chip!

I'm starting to lose hope that this one is going to be
an easy fix....... haha!

[Paul678]

Re: Compaq Presario C700 No Video at All

Did it have a pad instead of thermal paste that has come off?
Perhaps try a copper shim- duel effect of moving heat and a bit of pressure onto the chip

Yeah, it had a white, rubbery heat pad.

But surely the chip can't overheat and shut down immediately
before the BIOS boot-up. Again, the video never shows
up on either the main screen, or an external VGA monitor
(and yes, I pressed "Fn" and F4 to toggle what appears
to be the external display, and still nothing).

So even if I heatsink it properly now, the chip is still not
likely to work.

I'm thinking of parting this unit out........

[momaka]

Re: Compaq Presario C700 No Video at All

Well, I was watching this xBox 360 video http://www.youtube.com/watch?v=1lRdAFyvrX4
So I'm sure it would be a similar procedure in my case, but I've never done this before, and again, I don't have a heat gun, or hot-air station.

You can also do a reflow in a regular oven, too. Just make sure to cover all of the plastics with aluminum foil and not to move, shake, or cause the oven to vibrate, otherwise components might start falling off.
For the reflow, set the oven to 220-225C. Once the board reaches that temperature, let it sit for about 20 seconds, then turn off the oven, *carefully* open the oven door and let the board cool down to a temperature where you can safely touch it with bare hands (so about 20-30 minutes). Also, if you want the reflow to last longer, it is recommended to add a few drops of liquid or paste flux under the graphics chip before you put it in the oven.

How do you keep the caps on the other side of the
board from falling off? Is the heat dissipated by the PCB enough so that you don't have to worry about that?

With heat gun/hot air/or IR heating machine - yes. In the oven, no, you have to be careful, especially if you have flux run off onto nearby components.

Is there a way to test for shorts on the graphics chip with only a DMM? Just to make it's shorted or blown out?

Not really. Depends on the chip. Some chips have a somewhat higher resistance (20 to 100 Ohms) so getting a very low resistance for one like that could possibly indicate a bad chip. But more often than not, CPUs and GPUs have very low resistance (under 10 Ohms), so it's hard to tell if they are shorted or not.
So in general, testing a test graphics chips and CPUs with a DMM will give very little useful information.

[Paul678]

Re: Compaq Presario C700 No Video at All

You can also do a reflow in a regular oven, too. Just make sure to cover all of the plastics with aluminum foil and not to move, shake, or cause the oven to vibrate, otherwise components might start falling off.
For the reflow, set the oven to 220-225C. Once the board reaches that temperature, let it sit for about 20 seconds, then turn off the oven, *carefully* open the oven door and let the board cool down to a temperature where you can safely touch it with bare hands (so about 20-30 minutes). Also, if you want the reflow to last longer, it is recommended to add a few drops of liquid or paste flux under the graphics chip before you put it in the oven.


With heat gun/hot air/or IR heating machine - yes. In the oven, no, you have to be careful, especially if you have flux run off onto nearby components.


Not really. Depends on the chip. Some chips have a somewhat higher resistance (20 to 100 Ohms) so getting a very low resistance for one like that could possibly indicate a bad chip. But more often than not, CPUs and GPUs have very low resistance (under 10 Ohms), so it's hard to tell if they are shorted or not.
So in general, testing a test graphics chips and CPUs with a DMM will give very little useful information.

Thanks for the info, Momaka.

Based on what I've written so far, would you suspect that
a reflow would be enough?

Or would you think the chip is bad?

Do you think finding a new chip and replacing it
would be doable?

[popeye]

Re: Compaq Presario C700 No Video at All

needs new GPU not something you can replace easy way for you would be replacemaent pcb when fitted replace pads and heatsink past don't over do the paste.

[momaka]

Re: Compaq Presario C700 No Video at All

Do you think finding a new chip and replacing it
would be doable?

Replacing or re-balling the chip is more complex than just reflowing it. You will definitely need a rework station for that or you will need to go to somebody who has one. A reflow on the other hand is just as easy as baking/heating the board. If you are thinking about parting out the laptop and scraping the board, then you have nothing to lose to try the oven reflow. Just remove everything from the board (CPU, CMOS battery, wires, etc.), make 4 aluminum foil balls and place them at the corners of the board, then put the board in the oven and bake it like I mentioned in the previous post.

[Paul678]

Re: Compaq Presario C700 No Video at All

Replacing or re-balling the chip is more complex than just reflowing it. You will definitely need a rework station for that or you will need to go to somebody who has one. A reflow on the other hand is just as easy as baking/heating the board. If you are thinking about parting out the laptop and scraping the board, then you have nothing to lose to try the oven reflow. Just remove everything from the board (CPU, CMOS battery, wires, etc.), make 4 aluminum foil balls and place them at the corners of the board, then put the board in the oven and bake it like I mentioned in the previous post.

Ok, did the reflow, and still nothing.

So now I'm looking at motherboards:

http://www.ebay.com/itm/160755181692...84.m1438.l2649


But it's a bit of a gamble, but not too bad at $17.

What has been the experience with you all, in terms
of luck with "untested, As-Is" Ebay motherboards?

[popeye]

Re: Compaq Presario C700 No Video at All

Ok, did the reflow, and still nothing.

So now I'm looking at motherboards:

http://www.ebay.com/itm/160755181692...84.m1438.l2649


But it's a bit of a gamble, but not too bad at $17.

What has been the experience with you all, in terms
of luck with "untested, As-Is" Ebay motherboards?

waste of time you need a working one tested .

[Paul678]

Re: Compaq Presario C700 No Video at All

waste of time you need a working one tested .

Ok, what about this one?

http://www.ebay.com/itm/HP-Motherboa...item416520cca5

About $30 total, but supposedly tested working, with
14 day warranty.

I emailed the guy, just to get some more info on the history
of these boards, and he hasn't responded for 2 days or so.
I guess they are busy, but it's nice to get a response before
you fork over cash......

[Paul678]

Re: Compaq Presario C700 No Video at All

Ok, got the new motherboard, and it worked well,
but I had a bad wire or two in the video cable, which
intermittently made the screen turn white on boot up.

I know I should have properly bought a new cable, but
after opening it up, the bad wire was so obvious I figured
I could just solder it, and the computer does boot up
from a Linux Live-CD, no problems.

Funny, even on Craigslist, not too many people are selling
SATA laptop hard drives......I may have to do NewEgg.....

Anyways, thanks for all the responses for another
successful repair!