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Old 05-26-2019, 06:47 PM   #15
momaka
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Default Re: Need help with Shuttle SB83G5A - fans spin but that's all

Quote:
Originally Posted by momaka View Post
Now the question is whether I should try re-flowing the CPU socket BGA or just insert something underneath it to put pressure on the board.
Well...
I tried putting a spacer on top of the rubber foot that was underneath the CPU socket, and with that, I could not get the motherboard to post at all, no matter whether I inserted pressure on top of the CPU socket or not.

So I removed the spacer and tried again. Got the motherboard to post reliably every time I put pressure over the CPU socket area (tested about 5-6 times.) On that, it's interesting to note here that once the motherboard boots, I can stop inserting pressure over the CPU socket, and the motherboard will continue to work, so long as I don't power-cycle the machine (soft reboot is fine, though.)

While at it, I took a few moments to play around inside the BIOS. Unlike major OEM's BIOSes, Shuttle seems to have left the BIOS for this motherboard pretty much stock from the motherboard's manufacturer (which I suspect is Jetway, though I can't really confirm.) And being a Phoenix BIOS, it actually had pretty decent overclocking and tuning/tweaking options, including BUS speed selection. I tried 250 MHz instead of the stock 200 MHz (meaning the 2.8 GHz CPU in there should run at 3.5 GHz)... but that was probably too much of a push and the mobo ended up not POSTing (until I reset the CMOS again, that is.)

So yeah... I might come up with a temp solution to have pressure inserted over the CPU area to get the PC to work again, just so I can play around with it for a bit. But other than that, it's probably going to end up being a reflow at some point in time. Just have to see when. I have a few video cards in the cue before this... and a few other projects before those. On top of that, I just started a new job a few weeks ago, so I've had less time to work on my personal stuff. (And then there's Fortnite - a major drain of my free time after work, lately.)

Quote:
Originally Posted by Dan81 View Post
The LGA is the only thing to reflow as I understand it. Add some flux, then blast that socket with a heatgun
Yup.
Will do.
Probably will be stovetop gas burner + heatgun, though - that way, I get more even heating from top and bottom. Not to mention the stovetop gas burner does the majority of the work. Even on its lowest setting, most boards I put on it will reach 150-170C within 3-7 minutes, which is actually a decent "heating curve" for a reflow profile. Then I turn on the heat gun and to get things to the right reflow temperature.

Quote:
Originally Posted by Retro-Hipster View Post
I love the details! This has been a fun read. I applaud you for your effort and work.
Thanks!

Quote:
Originally Posted by Retro-Hipster View Post
haha That desoldering wick hack is a thing of beauty.
Yeah, ghetto mods at their finest! But that's all I could come up with at the time.
I did do another motherboard even better, though - that one has all MOSFETs with their tab free-standing in the air. So for extra cooling, I soldered a bunch of used braid to each one. Not sure how much that helps, as I've yet to commission that motherboard into use. But over the time I've used it (quite a few 2-3 hour-long sessions), it's been stable and cool-running. But anyways, that's a showcase for another thread, perhaps. I've finally gotten into a phase where I am building PCs with my spare fixed junk on a more regular basis. So within a year or two, I should have most of my stuff posted.

Quote:
Originally Posted by Retro-Hipster View Post
I think the question of "Should I reflow the processor" would depend a bit on your skill and comfort level. lol Reflowing larger BGA chips can be nightmarish/prone to disaster. That being said, if it's already broke and that seems to be the only solution, maybe you don't have much to lose? Additionally, if this is to be a learning experience, it might be worth it just for that! I mean, you did essentially do the troubleshooting work. :p
Well, I've actually done some work on large BGA chips (PS3 GPU chips, anyone?) and that's exactly why I am a bit put off. As I remember, the biggest problem with large BGA chips is that the board tends to warp under its own weight and due to the different expansion rates of materials in the CPU/BGA area.

And with LGA 775 socket, I need to see if there is a way to take apart the metal pieces from the CPU socket, as I imagine they might add too much weight on the BGA and crush things in there, thus opening the possibility of the BGA bridging.

But other than that, at least heat-wise I shouldn't have any issues, as I plan on doing this on my gas burner + heat gun, just as I've done many of my other successfull "home-brew" reflows now.

Quote:
Originally Posted by Retro-Hipster View Post
If you do end up re flowing it, I would just make sure and give it plenty flux so that it can penetrate up under the chip/between the bga. I probably wouldn't do a rework on it unless you happen to a good purpose made solder paste and a stencil, but then again I'm not very good at this. lol
Oh, who needs stencils when you can manually place the balls one by one.
(Don't ask - I've actually had to do it once. But it was on a smaller chip. And what I did is I used a "general purpose" stencil that has holes in a big square pattern. So I just used that stencil to place most of the balls on the chip and then removed the "extra" ones that the chip didn't have pads for. Took a little over an hour just for that, but it's doable.)

Last edited by momaka; 05-26-2019 at 06:53 PM..
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