Question about 85c caps vs. 105c caps

[PCBONEZ]

Re: Question about 85c caps vs. 105c caps

The only thing that only concerns me is whether the VR capacitors will last and whether or not a capacitor that doesn't look aligned to the board immaculately (even in the slightest) might be a problem...

Can not tell you.
Sometimes they lean then when they are pushing the bung out.
OFTEN they simply were installed crooked.

I do think given how old the motherboard is that the CMOS battery could be the culprit, but the only way to tell is to move the 3-pin (clear/reset CMOS) jumper or get a new battery.

CMOS Reset won't help you.
All that does is short the battery long enough to wipe BIOS settings.
[Procedurally you turn off the +5vsb supply first. AKA Remove AC power.]
If the battery is dead the settings are already wiped [reset] as soon as you turn off +5vsb.
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I suggest you check the battery voltage with a meter or just get a new battery.

is there a risk in using the back on/off switch in lieu of the front one to power the computer on and off?

The switch on the back is like unplugging it from the wall. To the system it the same as a power outage.
Not safe unless the system is already shutdown because the hard drive might be busy doing a maintenance task.
The one on the front panel does not denergize standby power [+5vsb] so it isn't 'off' like you are thinking of off.
It's not off-denergized, it's actually just in standby. It also lets the hard drive(s) finish before it 'kicks in' and shuts it down.
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[Wester547]

Re: Question about 85c caps vs. 105c caps

I should be clearer - just before the PSU was superceded, the system would automatically power on but I would receive no CMOS error. After switching power supplies, the error came to bear. Great information. I do think given how old the motherboard is that the CMOS battery could be the culprit, but the only way to tell is to move the 3-pin (clear/reset CMOS) jumper or get a new battery. The only thing that only concerns me is whether the VR capacitors will last and whether or not a capacitor that doesn't look aligned to the board immaculately (even in the slightest) might be a problem... also, is there a risk in using the back on/off switch in lieu of the front one to power the computer on and off?

[PCBONEZ]

Re: Question about 85c caps vs. 105c caps

Could it be a result of something corrupted in the BIOS then (or the chipset)? I know the power supply isn't bad. The system started doing this before the PSU was replaced. Could it also be a broken switch in the front? Not laying doubt to your answer, just asking. ^^; This could be something the other dying PSU ruined in the setup as well.... right?

No. BIOS won't do that.
The BIOS code [program] in CMOS does not run until -after- it starts.
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A bad switch could do it.
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And a bad small cap could do it by not holding it's charge or by being partially shorted. [Not likely to be a large cap in any of those circuits.]
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If you have a chip with a "Wake On" function [like wake on LAN, etc...] that has gone dodgy then that could be switching it on due to a fault in it's circuitry. (Including caps.)
All a 'Wake ON" function does to start the system is pull the pin on the chipset down via a different path.
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[PCBONEZ]

Re: Question about 85c caps vs. 105c caps

And another thing about capacitors is that I would think that CPU usage would affect the capacitors around it since some of them are voltage regulators, and high CPU usage is known to be a problem with defective capacitors.

Capacitors are not voltage regulators.
They smooth and filter the output of voltage regulators.
[Ummm, most on a mobo anyway. They have other jobs in different apps even on a mobo.]
Loading on the CPU has no affect on caps *in that way* because the CPU power doesn't go -thru- them. [It is DC.]
What heats caps is Ripple which is a semi-random AC.
Ripple is the 'noise' [voltage spikes] made when transistors [in this case in the CPU regulator aka VRM] turn on and off. In a CPU VRM one set of transistors lowers voltage by intermittently connecting to ground [on-off very fast] and another set raises voltage by intermittently connecting to +12 [on-off very fast]. The final voltage to the CPU is where the raise and lower balance out. The transistors switch on-off something like 50k-100k times a second thus the ripple frequency there is 50kHz to 100kHz.
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[PCBONEZ]

Re: Question about 85c caps vs. 105c caps

I recently bought a surplus Intel 845gvsr motherboard. Everytime you turned on the power strip the board would start up. The problem was a dead cmos battery. The default in the bios is "boot after power failure". Once I replaced the cmos battery and changed the bios setting, it would stay off until the power button push pressed.

They'll all do that if you cut AC line power and the battery is dead.
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On modern boards the CMOS is powered from +5vsb through a step down.
The battery only powers it when there is no AC and hence no +5vsb.
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Basically if you never cut AC then you won't be running the battery down.
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[Wester547]

Re: Question about 85c caps vs. 105c caps

Thanks for that helpful inkling of input. That sounds like a coherent explanation to me. Of course, it could be the the pin on the chipset as well, but it's hard to say.

[jamesbo]

Re: Question about 85c caps vs. 105c caps

I recently bought a surplus Intel 845gvsr motherboard. Everytime you turned on the power strip the board would start up. The problem was a dead cmos battery. The default in the bios is "boot after power failure". Once I replaced the cmos battery and changed the bios setting, it would stay off until the power button push pressed.

[Wester547]

Re: Question about 85c caps vs. 105c caps

Could it be a result of something corrupted in the BIOS then (or the chipset)? I know the power supply isn't bad. The system started doing this before the PSU was replaced. Could it also be a broken switch in the front? Not laying doubt to your answer, just asking. ^^; This could be something the other dying PSU ruined in the setup as well.... right?

And another thing about capacitors is that I would think that CPU usage would affect the capacitors around it since some of them are voltage regulators, and high CPU usage is known to be a problem with defective capacitors.

[PCBONEZ]

Re: Question about 85c caps vs. 105c caps

I was pondering about the computer automatically powering up. Can't that also be the resulting consequence of a dead CMOS battery

No.
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When you push the start button it temp grounds a pin on the chipset and that initiates start-up. [It's not a full ground. It's called to 'Pull Down'] The pin is normally powered [aka 'Pulled Up'] by +5vsb through some other circuitry. If +5vsb drops the volts on that pin can go low which looks to the chipset like it's grounded.
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[PCBONEZ]

Re: Question about 85c caps vs. 105c caps

Do you think a 1200RPM case fan would be too much for that,

Just 1200RPM doesn't tell me anything.
It's CFM that matters and that varies with: RPM, diameter, thickness, number of blades and pitch/shape of blades.
You want at least 40 CFM for a side fan and more is lots better.
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Probably take two fans but if you can get 100 CFM [filtered] going in the side you can usually get rid of the other case fans because the positive pressure will push air 'out' through where they were and that keeps inside the case cleaner.
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[Wester547]

Re: Question about 85c caps vs. 105c caps

Do you think a 1200RPM case fan would be too much for that, or do you think it could be pointed to the motherboard without disrupting upon the airflow of the PSU fan and the CPU fan in tandem?

It is a bit small though, so I don't even know if there's room for another fan. That is to say, the case isn't small, but the motherboard somewhat is. As an update, I loaded the CPU to 100% last night for an hour in a half in 3D full acceleration. It was rather cold weather, however (for California), being at around 48F, so the CPU was only up to 44-45C at full 100% load, and the motherboard and auxiliary ranged from 35-37C, with the hard drives at 33C and 35C respectively (the ST3250824A and ST3160023A). After doing that, I shut it down and took off the side panel, and felt the motherboard, along with the RAM, capacitors, CPU, etc. The 105C capacitors did feel somewhat warm after that, but they're Polymers and 105C Nichicon HDs so I know they're good. As did the CPU and GPU (even colder, though) - slightly warm air could be felt around that area, though nothing grave. To my relief, the 85C caps felt significantly cooler, even though they were right next to the RAM, which also didn't feel hot. I guess the RAM might not be a problem because it's in a large enough case not to heat up too much.

I was pondering about the computer automatically powering up. Can't that also be the resulting consequence of a dead CMOS battery (as it is unable to retain the last state the computer was in so automatically powers on the system with the default BIOS values - in the BIOS, it is set to automatically power on after it loses power)? It does beep two times as the error comes up. And would it be seen as dangerous for any of the components to use the power switch in the back to power the system on and off by contrast to the case switch in the front? (what would usually be used)

And right, it says VR(M), not VRM. ^^; And if a capacitor doesn't look like it's impeccably aligned to the board, does that mean it's irrevocably bad (I know the main Badcaps page says something to that effect, but I'm just curious)?

[PCBONEZ]

Re: Question about 85c caps vs. 105c caps

I have another question. If CPU and graphics card fans are fast enough at removing the heat they generate, then what about hard drives that have no fans blowing over them? Would they contribute to the heat capacitors succumb to? In my case, I ask because before I was given this machine it had a ST3160023A and WD800JB running in the same enclosure and they both ran somewhat hot - 40-50C average, I would say. The chassis for the hard drive has holes drilled into it in the back where the hard drives presumably exhaust heat and seem somewhat far from the motherboard as a whole, but would that be enough to curtail the life of the 85c capacitors? Also, could bad PSU caps cause more ripple current and show absolutely no signs of it?

Also, if a graphics card runs as hot as 90C at load and doesn't exhaust heat outside the case, even with a fan, wouldn't that heat up the capacitors too (along with the capacitors on the card, even more so?)? ^^; I hope these aren't too many questions.

Yes, all the CPU & GPU fans do is move the heat from the chip to inside the case.
The case fans and PSU fan are then supposed to blow it out.
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I fix cooling issues by adding a filtered fan that blows 'in' to the side panel such that it blows on the mobo.
Not only does that get more air going -through- the case it creates some turbulence which helps prevent low-flow hot-spots.
And, since it's filtered it helps keep the dust bunnies off the mobo itself.
- I prefer a 120mm low RPM side fan because I can get decent air-flow without using a noisy high RPM fan right where I'll hear it all the time.
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[PCBONEZ]

Re: Question about 85c caps vs. 105c caps

Also, the exact CMOS error is:

CMOS/GPNV Checksum Bad

Does that seem like a capacitor issue to anyone?

All by its self that sounds like a bad CMOS battery.
A bad cap could be discharging the battery.
Can't say without some workbench time.

Also, the computer powers on automatically whenever I turn on the power strip and/or power switch in the back of the case.

This sounds like a problem with +5vsb dipping low.
Usually that's a PSU issue but there are ways a bad cap could do that too.
Can't say without some workbench time.

Something I noticed is that the motherboard is a bit small and the two 512MB RAM sticks are right next to the VRM Nichicon 85C caps, and I imagine the RAM gets a bit warm.... could this spell a problem for the capacitors?

They are VR not VRM. The (M) is the tolerance code for uF. (M) = +/-20%
Of course they can get hot right next to RAM.
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[Wester547]

Re: Question about 85c caps vs. 105c caps

Also, the exact CMOS error is:

CMOS/GPNV Checksum Bad

Does that seem like a capacitor issue to anyone? Also, the computer powers on automatically whenever I turn on the power strip and/or power switch in the back of the case.

Something I noticed is that the motherboard is a bit small and the two 512MB RAM sticks are right next to the VRM Nichicon 85C caps, and I imagine the RAM gets a bit warm.... could this spell a problem for the capacitors?

[Wester547]

Re: Question about 85c caps vs. 105c caps

I have another question. If CPU and graphics card fans are fast enough at removing the heat they generate, then what about hard drives that have no fans blowing over them? Would they contribute to the heat capacitors succumb to? In my case, I ask because before I was given this machine it had a ST3160023A and WD800JB running in the same enclosure and they both ran somewhat hot - 40-50C average, I would say. The chassis for the hard drive has holes drilled into it in the back where the hard drives presumably exhaust heat and seem somewhat far from the motherboard as a whole, but would that be enough to curtail the life of the 85c capacitors? Also, could bad PSU caps cause more ripple current and show absolutely no signs of it?

Also, if a graphics card runs as hot as 90C at load and doesn't exhaust heat outside the case, even with a fan, wouldn't that heat up the capacitors too (along with the capacitors on the card, even more so?)? ^^; I hope these aren't too many questions.

[PCBONEZ]

Re: Question about 85c caps vs. 105c caps

See page 86-87.
RoHS is not mentioned at all.

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[PCBONEZ]

Re: Question about 85c caps vs. 105c caps

A D845PEBT2 is probably too old to be RoHS anyway.
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[Wester547]

Re: Question about 85c caps vs. 105c caps

Thanks for the reply, very studious links. I didn't think lead free solder was too durable, I'm just hoping that it won't affect the useful lifetime of a desktop board. But has anyone ever measured the temperatures that electrolytic capacitors tend to run at with, say, stock cooling? Would it be room temperature or give or take 20 degrees higher?

[mariushm]

Re: Question about 85c caps vs. 105c caps

I sincerely doubt there's any difference between mountings of CPU.

That socket with loads of pins HAS to be soldered onto the PCB and guess what... when they solder all the surface mount components with lead free solder, do you really think they're going to move the whole PCB through a second machine/oven to solder a single socket with lead based solder?

No, there may be sockets with certain metal alloy in the pins that works better with lead based solder but I'm sure they also the other kind of sockets.

You probably got confused by "tinning" which just means those pins are pre-tinned with a very thin layer of solder to prevent oxidation and other things.

With modern boards you really shouldn't find lead anywhere - everything is lead free, which unfortunately is an issue as lead free solders are not as good ... tin whiskers, different behavior when it comes to resistance to bending and vibrations and so on.

You can find a pretty good paper here (and it has pictures, copy and paste url as it's a weird one and this forum software doesn't think it's a valid url) :
Reliability and Failure Analysis of Lead-Free Solder Joints

http://www4.uic.com/wcms/Images.nsf/%28GraphicLib%29/IPCNewOrleans.pdf/$file/IPCNewOrleans.pdf

NASA also released a slideshow in pdf document here:


This article is also a good read, about tin whiskers and military issues caused by this phenomenon:
http://www.militaryaerospace.com/art...he-making.html

What is the best way to ensure capacitors are kept cool? More system fans directed to the motherboard? Side panel off?

Just leave it like it is, simply making sure air moves around in the case naturally.

Again, the motherboard temperature reads around 35C usually and the Auxiliary a bit higher but still below 40.... would those temperatures affect the capacitors? Also, all the capacitors should be sitting flush to the motherboard, right? Not even the slightest exception?

The motherboard detects those temperatures using a couple of sensors in various parts of the board. The sensors are like regular resistors/small capacitors or surface mounted components...
The main sensor is usually connected somewhere that's bound to be hot, so if it's saying 35 degrees it may very well be right under the VRM chips, which control the power going to the processor. These are by default hot, as they're 24/7 generating the power used by the processor. Capacitors 1-2 centimeters further away may be at 20-25c or room temperature.
Auxiliary may also be somewhere near the memory slots, for example, or may not even be connected and what you see is the default value for that sensor. You may also see the sensor being heated up by the warm air the fan pushes down on the heatsink of the CPU cooler and then floats sideways in the area around the CPU hitting the sensor as well.
So keep in mind just because these sensors say 35-40c, it doesn't mean 1-2 cm/inches from them the motherboard is still 35-40c
The only way you'd know for sure is using one of those laser/infrared thermometers

[Wester547]

Re: Question about 85c caps vs. 105c caps

Does anyone know if BGA has been a problem with regard to motherboards or chipsets themselves (in desktops)?

And mariushm, thank you also for the reply. Very intriguing information. (:

What is the best way to ensure capacitors are kept cool? More system fans directed to the motherboard? Side panel off? Again, the motherboard temperature reads around 35C usually and the Auxiliary a bit higher but still below 40.... would those temperatures affect the capacitors? Also, all the capacitors should be sitting flush to the motherboard, right? Not even the slightest exception?