Question for Computer/Electronic gurus?

[TopCatGr58]

Hey folks, Randy, 3phase, etc.,

I helped a coworker's son rebuild a 'puter he had fried with a bad power supply, had to replace a Mobo. The Mobo had worked the first time I replaced the power supply, but he had some funky house wiring and the 2nd PS also fried, but took the Mobo with it that time! Got it fixed with a replacement Mobo and 3rd PS, and they had the house wiring checked/fixed!

I was looking at the fried mobo, thought I had read where it's often a CAPACITOR that gets fried when the PS overloads it!?

There is a smaller capacitor proximal to the PS plug on the mobo, and UNLIKE the rest of the capacitors on the board, the nice shiny aluminum end plate appears to be bowed outward, whereas the rest of the capacitors all are nice and flat or even slightly concave! Does this description of the slightly flexed endcap on a capacitor sound plausible for a culprit/indicator of a blown cap.?

I don't have a special electronics gauge/tester/logic probe, just a simple ohm/volt meter, but I think is has a DIODE setting on it? How can I test the suspect capacitor along with the others? There is printing on the capacitors so I should be able to decipher it's rating, but don't know much about this stuff, vs. simple resistors and such! Can I test them while still connected to the Mobo, or will I get wrong info due to the wire connectors on the Mobo for the cap. possibly following another path thru the mobo instead of the cap.?

I just hate seeing a good P4 mobo go to waste, I have a few other fried Mobo's that I could harvest capacitors from(or even Rad. Shack), to possibly bring this mobo back to life......UNLESS aside from the capacitor if there is a strong possibility that the IC's/chips might have also gotten damaged with the power overload!?
T.C.

[The Lorax]

You can sort of test the capacitor with an ohm meter, (yes, the bowed out top is indicative that it is blown, usually these are polarized electrolytic caps and if they have voltage put across them in the reverse direction, they go "pop") remove the capacitor from the circuit, connect the ohm meter across the two leads of the cap, (this test works best with an analog meter, but can be done with a digital) watch the display, the resistance should start at almost zero, and gradually increase to infinity, (or quickly depending on the size of the cap) if it starts at infinite resistance, short the legs of the cap together to discharge it and repeat the test. you can feel free to check it if you like, but I'll bet it's fried. Electronic components are best checked out of the circuit as the rest of the circuit can give you erroneous readings. if you replace the offending capacitor, it is quite possible that the motherboard will come back to life, bad / damaged capacitors can load supplies and make stuff not work, the short answer, check it if you wish, replace it and try it, what do you have to lose? $.50 for a cap, maybe a buck, what do you have to gain? free motherboard....seems like a simple decision to me. have a nice day and ride safe

[JWSanders]

You will need a capacitor tester to test it properly, and it will have to be removed from the board. A tricky proposition, considering most mobo are multilayered. If you carefully desolder it, you may be able to get it out cleanly.

You can also use an ohmmeter to test it once it's out of the circuit. It may work to a degree in-circuit, but you could also get readings from other caps that may be filtering that input with that cap.

Ideally, a capacitor will present a growing resistance as it charges off the OHM meter's voltage. Short the leads of the capacitor, set the meter to 10k ohm or so, the put them on the cap's leads. It should go to zero immediately then climb in resistance until it charges to unity with the meter leads. Will go to infinity or really high (20+ mega) ohms. With smaller value caps, this may happen faster then a digital meter can see.

If it stays at zero, it's shorted.

Sadly, usually when a power supply fries a mobo its due to overvoltage on one or more outputs, which fries the regulator for that voltage and subsequently causes the cap filtering it to fry (or bloom) like you describe on that cap.

I guess it's worth a try though...

[JWSanders]

lol, was late by 2 minutes

[3Phase]

Hey, T.C., there was a spate of motherboards with bad electrolytic capacitors a while back. Double-check the ones around the voltage regulators by the processor socket.

If the top's bulged on a capacitor I wouldn't even bother testing it, just get a new one. Pay attention to how the capacitor is soldered to the board as electrolytic capacitors (and a few other types) are polarized with the Positive and Negative leads marked. Do not reverse them unless you just like to practice replacing blown capacitors and cleaning electrolyte and gunk off yourself and the board.


The capacitor should be marked like:

- - - - -
35V .47uF
+ + + + +


It's entirely possible that one of the 'spendy, proprietary, ICs nobly sacrificed itself to try to save that two cent capacitor, but take it one thing at a time.

Replace the bad cap, put the board inside some type of box/container, then power it up with nothing in it - no memory, processor, video, etc. Listen for error beeps, hissing, small pops, large explosions and watch for smoke leaks.

If it survives, add a processor and try again
If it survives, add memory and try again
If it survives, add video and try again
If it survives, add a mouse and keyboard and try again
If it survives, add a floppy drive and try again
If it survives, try to boot a FreeDOS floppy or Win98 Rescue disk
If it survives, add a hard drive and try to boot it

C:\WINDOWS\run
run. windows
run.





Regards,

Scott

[Ivan]

If it survives, add a processor and try again
If it survives, add memory and try again
If it survives, add video and try again
If it survives, add a mouse and keyboard and try again
If it survives, add a floppy drive and try again
If it survives, try to boot a FreeDOS floppy or Win98 Rescue disk
If it survives, add a hard drive and try to boot it

C:\WINDOWS\run
run. windows
run.

fdisk /mbr
format C:
install windows.
patch windows to SP38.7beta4
reboot.
fdisk.
reboot
format c:
reboot
fdisk /mbr
reboot
reboot
try win98
upgrade to NT
upgrade to XP
reboot.
patch
reboot
reboot
damnit
reboot


Its worth noting that most people use windows since Linux is harder to install.

[The Lorax]

Linux might have been more difficult to install, but I don't think that is still so. I put an older version of SuSe Linux (7.2) on a system a few moths back, I didn't find it terribly difficult to install. I do find it significantly more stable than Windows, I'm not terribly adept at using it, but I rather like it. unfortunately, one of the carpet rodents yanked it off and put Windows 98 on it. no matter, I build a better system and re - install it hee hee. if nothing else, I'll learn something new (I do every time I go to install an OS on a computer, even Windows). All I got, have a nice day and ride safe

[3Phase]

Good points, all!

I didn't really want to proselytize for any one OS or another in a hardware thread, just help T.C. test the motherboard to see if it works or not. He can make his own decision about what to install and run afterward. FreeDOS is, well, free and has no known copyright (why does the vBoard editor captalize the first instance of the word 'copyright' in this first paragraph but not others?) issues and Win98 boot disks are ubiquitous.

However, copyright (you knew that was coming, did you not?)

since LINUX has been mentioned along with Window's installation, stability, and patch issues I have to say that installation, security, packages, applications, support, library dependencies, and copyright issues plague all software and all flavors of free UNIX. For personal reasons I have not ever and will not ever use LINUX.

I'm not a MS fanboy, but Bill's stuff worked as advertised for me and I've had three years of free updates so I'm satisfied if not exactly ecstatic. My first XP install was in June 2005 and I'm still using it. Large chunks of the hardware underneath my original XP installation have gone to silicon heaven (where all the old calculators go!) but the software has outlived a lot of the hardware - including the case.

At this late date I'm still using XP because it's the only OS that has working drivers and software for my X-Fi Sound Blaster Pro and because it just keeps going. Vista ripped the guts out of direct hardware access and has some other, less savory, issues so it's out of consideration.

My old favorite, FreeBSD, will be reinstalled and tuned before support for XP runs out but I'll lose my Sound Blaster X-Fi Pro. Oh well ....


Regards,

Scott

[TopCatGr58]

Hey all,

Appreciate the info, here's what I have found and what I need!

Removed the swollen cap, it's 10V 470uF, 6mmX11mm, 105 C rated.

Went to Radio Shack, they have these massive 470uF but 35V caps!

Started looking online, found a distributor www.newark.com with several brands listed, ie. Multicomp; Panasonic; Rubycon; etc.!

The Rubycon is 8mm x 11.5mm, so I can make it fit, is rated at some 20khours vs. some of the others that were only rated at 2k hours? And it's surprisingly cheap, like $0.25c or such each, but may have to buy 5 ! It's Aluminum electrolytic Radial style/shape, the picture looks just like the one I have.

BTW, when I tried to test the cap, using the Ohmeter, it would start out with Kohms, then climb to Mohms and level off at about 3.5Mohms, then I switched the gauge to DCV and it would register about 0.5V. The Cap did seem to get warm after a few runs with the Ohmeter, but it did not show Zero Resistance=shorted, but it's definitely swollen!

Do any of you Electronic geeks have one of this size/range you wouldn't mind sending my way?? Otherwise, I can order it online!

Now as for the OS, I, too, am not a MS FANATIC, but it has worked for me as well, especially XP..I held out with 98SE as long as I could, got XP Dec. '05 so I could upgrade the version of Vid Edit software I was using. IT has been VERY STABLE for me, and recognizes all of the hardware I have. I am also leary about getting Vista when I build my new system hopefully this Xmas! I actually OWN/paid for my XP Home Ed. that I have, so I have no qualms about using it on my new system, but I've read about where Vista is actually faster with the new generation CPUs and Ram in Video Editting functions and such!? Maybe I'll figure out how to have a DUAL BOOT system so I can compare, but I don't want to shell out the $$ for Vista if I don't have to!?

Speaking of FreeDos, was working on an older ComPaq-crap, D/L'd the bios upgrade utility from the manufacturer with FreeDos on it, and it would HANG, giving an annoying beep and a phrase I can't recall. I finally created a boot disk from an old Win98 one, and was able to perform the Bios upgrade, but was surprised that what was provided by the manufacturer wouldn't work on the CPU/Mobo!?

I'm actually very good/adept and reinstalling OS's, rarely encounter problems unless I don't have the correct device drivers!
Thanks in advance!
T.C.

[randy]

TC, the 35v cap will work if you can stuff it in. On caps you can go up in voltage rating, you can't go down.

[TopCatGr58]

Thanks Randy, that's good to know. I might be able to get some off of an old Mobo now. Before, I think I had some the right uF size, but wrong voltage. But now I know that I can go UP, I'll double check what I have on my old Mobos.

But the one I took out is rated 105 C, the RS one is only 85C rated. I don't think they get that warm when they are working right, nor the inside of the 'puter with proper ventillation and fans, so do you think the 85C would be OK?
T.C.

[3Phase]

Not speaking for Randy, but 85C should be fine. I seem to keep stepping, and I do apologize, Randy. It's not intentional!

A great, honkin', 470uF capacitor at 10V is most likely a ripple/noise filter for a 5V or 3.3V line. A P4 motherboard or the processor's thermal management unit should throttle back the processor or shut down the machine if the processor gets to 55C or 65C. The internal, ambient temperature shutdown is usually lower than the processor.


Regards,

Scott

[randy]

No harm taken 3phase! We're all here for the same reason. TC, 85C is 185F! If things got that hot, you could soft boil an egg! The 85C unit woud be fine. And salvaging from another MB is a good way to go, I always keep blown boards for just that reason.

[LoserShoes]

Remember, running xp on a 64 bit system you still have a 32 bit operating system.
Lots of people really like Ubuntu.
Lack of support for certain hardware is a problem with Linux/BSD.

Steve

[JWSanders]

Just to add to the linux discussion....

If you want to try out one of the many Linux distributions, it's easy to do without needing a dedicated machine to do it on.

There is a suite of applications out there called "VMware". It allows you to run a virtual machine in a window. Basically, it can split your computer into several units and run an entirely different operating system in a window.

The easiest one to run is the "VMware player", found here. It's available for free.

After you get that the VMware site has what it calls "appliances". A vmware appliance is a fully self-contained operating system in a file. There are several different flavors of Linux appliances, including Ubuntu and OpenBSD, and running them is a snap. Just open the appliance with the player and you will be running a fully operable Linux system in a window.

It makes it very easy to get a feel for linux without having to dedicate a lot of time, effort, or hardware to do it.

There are even windows appliances. I have run 3 full instances of XP on the same machine, with no problems. There are even MacOS appliances, but they are not easy to find. (some torrent sites will have them, usually).

VMware's appliance section can be found here.