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#1
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Failed CMOS battery? Again?
OK, I have totally failed Gravity search. Amyway, my goal was to post this under my last post on the subject seems like November/December2014. At the time I was asking why my system clock seemed to stay where it was the last time the system was turned off rather than keep up. Seems to have happened again. Paul was explaining how the 2032 cmos battery should last up to 10 years if they were indeed fresh and the motherboard didn't have some kind of heavy load. Getting same same symptoms some 2 to 3 months after changing the battery last. Any reasonable troubleshooting before replacing the battery again? System was initially assembled in August 2014 with the initial 2032 failure about Nov/Dec2014 Z-97Pro/4790K/770 system T2 |
#2
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Failed CMOS battery? Again?
MrTsquare wrote:
OK, I have totally failed Gravity search. Amyway, my goal was to post this under my last post on the subject seems like November/December2014. At the time I was asking why my system clock seemed to stay where it was the last time the system was turned off rather than keep up. Seems to have happened again. Paul was explaining how the 2032 cmos battery should last up to 10 years if they were indeed fresh and the motherboard didn't have some kind of heavy load. Getting same same symptoms some 2 to 3 months after changing the battery last. Any reasonable troubleshooting before replacing the battery again? System was initially assembled in August 2014 with the initial 2032 failure about Nov/Dec2014 Z-97Pro/4790K/770 system T2 Well, something is draining the battery. What could it be ? (Detailed section of two Intel reference schematics, showing a 1K ohm resistor just after the battery.) http://i61.tinypic.com/2vsnfqs.gif You would measure the voltage across the resistor, to get an idea of current flow through it. The multimeter would have a 1 megohm or 10 megohm input impedance, which is relatively large compared to the 1K ohm resistor you'd be putting it across. With all PC power off (PC unplugged), 10uA comes from the battery. The 10uA, flowing through the 1K ohm resistor gives V = RI = 1000 * 0.000010 = 0.010V = 10mV You could probably just barely see this on the multimeter, on the 2V scale. If the current draw is higher than the suggested 10 microamp figure, the voltage across the resistor would be higher. That's the easiest way to verify the load. And if the load is above 10uA, there are a number of possible culprits. The SuperI/O might be connected to VBAT (not shown on the reference schematics, as the Intel schematics are "not all that real"). The Southbridge could suck more than the normal current. I don't know if the leakage or load spec is verified and chips with high leakage are discarded. It's also possible some transmission gate between the CMOS well and the rest of the Southbridge isn't working right, and phantom power flows into the rest of the chip. A "clear CMOS" jumper (CLR_RTC or similar), if left in the wrong position, could suck power. But then it probably wouldn't last 3 months while doing so, and you'd know as the BIOS settings would be constantly reset. ******* If you keep the supply connected and switched on at the back of the computer, the other diode path from the motherboard should have a higher voltage. By doing so, it "cuts off" the battery side diode, and prevents any current from coming out of the battery. And since the 3P3_standby or 3VSB source is "strong", it doesn't take no for an answer. Unlike the battery, with the 1K current limiting resistor in the way, the 3VSB source has no current limit. If there is a short there, then "something smokes" :-) Well, not really smoke, but what I'm saying is the 3VSB (with power supply switched on at the back), is a "stiff" source, and it can easily power a leaky load. So just keep the PC powered at the back, as your workaround. Yes, it costs a few dollars per year for electricity. Compare the cost (and time wasted) changing CMOS CR2032, versus the wasted electricity keeping the PC power supply on at the back. No more switching off at the power strip... Leave the standby voltage running on the PC at all times. (On an Asus motherboard, the green LED would be always lit.) That should stop the CMOS cell from discharging. If it did not, then maybe the dual diode itself, needs to be replaced. There might even be solder blobs, unintentional loads on the copper tracks. Which might be difficult to spot. I remember having a board in the lab that was "acting weird". I spent quite a while debugging, and stuck a scope on a particular track. And I could see a capacitor discharge curve (instead of normal square waves). I look at the board carefully with my magnifying glass, and the factory had stuffed the leg of a capacitor into the wrong hole! This caused the circuit to behave in unexpected ways (because now the circuit is no longer as I designed it). That's an example of "weird ****" happening when the pick and place machine slips and shoves a wire into the wrong hole. So even if you think you know how a circuit works, the staff at the factory can throw curve balls at you. There are a ton of ways that poor CMOS cell could have the charge leak away... Paul |
#3
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Failed CMOS battery? Again?
On Mon, 9 Feb 2015 17:01:08 -0800, MrTsquare wrote:
OK, I have totally failed Gravity search. Amyway, my goal was to post this under my last post on the subject seems like November/December2014. At the time I was asking why my system clock seemed to stay where it was the last time the system was turned off rather than keep up. Seems to have happened again. Paul was explaining how the 2032 cmos battery should last up to 10 years if they were indeed fresh and the motherboard didn't have some kind of heavy load. Getting same same symptoms some 2 to 3 months after changing the battery last. Any reasonable troubleshooting before replacing the battery again? System was initially assembled in August 2014 with the initial 2032 failure about Nov/Dec2014 Z-97Pro/4790K/770 system I'd contact the motherboard supplier and tell them that batteries are only lasting 3 months. -- Faster, cheaper, quieter than HS2 and built in 5 years; UKUltraspeed http://www.500kmh.com/ |
#4
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Failed CMOS battery? Again?
On Mon, 9 Feb 2015 17:01:08 -0800, MrTsquare
wrote: OK, I have totally failed Gravity search. Amyway, my goal was to post this under my last post on the subject seems like November/December2014. At the time I was asking why my system clock seemed to stay where it was the last time the system was turned off rather than keep up. Seems to have happened again. Paul was explaining how the 2032 cmos battery should last up to 10 years if they were indeed fresh and the motherboard didn't have some kind of heavy load. Getting same same symptoms some 2 to 3 months after changing the battery last. Any reasonable troubleshooting before replacing the battery again? System was initially assembled in August 2014 with the initial 2032 failure about Nov/Dec2014 Z-97Pro/4790K/770 system T2 Computers as clocks are traditionally bad timekeepers. Not keeping time is less a problem than losing enduser-set CMOS BIOS. A utility to autoconnect every few minutes to an atomic clock relay is an easy solution. (That's a bit radical, staying where the MB was last turned off. A system clock off a few minutes a month is more usual to what I've expect. Still, I wouldn't care as long as the BIOS settings haven't changed, that the battery at least ensures they stay that way for another 10 years.) |
#6
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Failed CMOS battery? Again?
In article , says...
MrTsquare wrote: OK, I have totally failed Gravity search. Amyway, my goal was to post this under my last post on the subject seems like November/December2014. At the time I was asking why my system clock seemed to stay where it was the last time the system was turned off rather than keep up. Seems to have happened again. Paul was explaining how the 2032 cmos battery should last up to 10 years if they were indeed fresh and the motherboard didn't have some kind of heavy load. Getting same same symptoms some 2 to 3 months after changing the battery last. Any reasonable troubleshooting before replacing the battery again? System was initially assembled in August 2014 with the initial 2032 failure about Nov/Dec2014 Z-97Pro/4790K/770 system T2 Well, something is draining the battery. What could it be ? (Detailed section of two Intel reference schematics, showing a 1K ohm resistor just after the battery.) http://i61.tinypic.com/2vsnfqs.gif You would measure the voltage across the resistor, to get an idea of current flow through it. The multimeter would have a 1 megohm or 10 megohm input impedance, which is relatively large compared to the 1K ohm resistor you'd be putting it across. With all PC power off (PC unplugged), 10uA comes from the battery. The 10uA, flowing through the 1K ohm resistor gives V = RI = 1000 * 0.000010 = 0.010V = 10mV You could probably just barely see this on the multimeter, on the 2V scale. If the current draw is higher than the suggested 10 microamp figure, the voltage across the resistor would be higher. That's the easiest way to verify the load. And if the load is above 10uA, there are a number of possible culprits. The SuperI/O might be connected to VBAT (not shown on the reference schematics, as the Intel schematics are "not all that real"). The Southbridge could suck more than the normal current. I don't know if the leakage or load spec is verified and chips with high leakage are discarded. Thanks, Paul. Not having appropriate test equipment and detailed knowledge of the board layout, I don't think I'll try for and voltage measurements. Also looks like that C15 0.1 microF cap if leaking a little might cause something similar. I'll send something to ASUS as well just to see what they say. I think I'll leave the power strip on for a day or so and see if that doesn't at least hide the symptoms. And then get a few more 2032 batteries. Totally O/T - I bought at an after Christmas sale 4 cute little electric candles - powered by 2032 batteries. tried 1 and it lasted for about a month when on for about 5 hours a day - timer built into it somehow. T2 |
#7
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Failed CMOS battery? Again?
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#8
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Failed CMOS battery? Again?
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#9
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Failed CMOS battery? Again?
On Tue, 10 Feb 2015 20:45:19 -0800, MrTsquare
wrote: Nope, wouldn't worry if I just had to adjust the time every few months, but this one just stops dead and then starts where is left off when the system is restarted. Me, neither - never heard of the likes. One of a kind. |
#10
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Failed CMOS battery? Again?
MrTsquare wrote:
OK, turned it on tonite after leaving the power connected to the PS all day since last nite. No change to symptoms. Still shows last night's date and time. Guess I need to just feed it a 2032 every few months. T2 You could connect a much larger battery to it. But that's soldering iron / hardware hacker type stuff. You need to use a battery with the correct voltage. (Voltage can't be too high, or the battery ends up "running the PC" all day :-) ) You'd locate something like this, check out the maH rating (i.e. to work out how many months it'll work), double-check the voltage is no more than CR2032 working voltage (must be more than 2.3V min). Buy a battery holder, a couple of wires. And be damn careful not to short something. Solder battery holder in parallel with CR2032 socket (access solder points on back of motherboard.) That particular battery is for running digital cameras with high drain, so has a relatively good peak current rating. If you short a battery like that, who knows, it might begin to swell. I would probably add a small series resistor, like 100 ohms, right on the battery terminal output, so a downstream short couldn't pop anything. http://www.all-battery.com/cr123_indvidual.aspx When I was a kid, and playing with batteries in the basement, I managed to develop enough current flow in dry cell batteries, to make the positive electrode "swell" and push out of the battery case. (Try putting about 30 batteries in series...) You don't want to be doing stuff like that. The reason nothing bad happened to me, is they weren't Lithium. I would think putting a fresh CR2032 in there, and leaving the power switch on the back of the computer in the ON position, should lengthen the time it lasts. If it does not, that tells you the fault is very close to the battery itself (socket, 1K resistor, or problem at or near the three-legged ORing diode BAT45C or similar). If the fault is further downstream, the ATX PSU takes care of it. The only thing that really stands out in circuits like that, is the SuperI/O hardware monitors that have a VBAT pin, for monitoring the CR2032. That's a possible place for draining the battery to happen. The CLR_CMOS jumper is another candidate location. Inspect for dirt or solder splashes or tin whiskers. The rest of it, the CR2032 socket, 1K resistor, ORing diode, probably not as likely. Have you ever used the CLR_CMOS jumper before ? If so, did you leave the system powered when doing so ? On some systems, this damaged (burns) the three-legged ORing diode. And your leak could be there... Paul |
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