CMOS checksum fails

On Sat, 16 May 2015 18:56:54 +0200, "Skybuck Flying"
wrote:

Ammount of dust was pretty huge.

The accumulation of dust in your machine is a fairly good indication
of what you are breathing. You might try finding the source and
eliminating it. Over the years, I've found fiberglass ceiling
insulation sucked into the HVAC system and collected by the computer
fan to be a major problem for both the user and the computah. This is
what I use to find sources of dust and smoke:
http://802.11junk.com/jeffl/crud/Nikken-AQM.jpg

I used vaccuum cleaner to suck out most of it.
I also blew myself across the motherboard to blow out hidden dust cloths and
stuff.

Don't use a vacuum cleaner. It doesn't remove the dust very well.
Much more effective is an air compressor to blow the dust out. I have
three small (1HP) compressors (home, office, and car) for cleaning
machines. I clean literally everything outdoors before it is dragged
into my office, which has drastically reduces my office cleaning
chores.

Also, you might want to measure the voltage between the vacuum cleaner
hose and a nearby ground. The rotating rubber belt is very close to a
Van deGraff generator. I've seen a few generate some rather high
voltages. Fortunately, the problem seems to be known and modern
vacuum cleaners don't seem to have the problem.
http://skeptics.stackexchange.com/questions/18668/is-it-dangerous-to-vacuum-clean-motherboards-and-other-electronics

I noticed there was quite a large build up of dust around and on the
battery.
So my theory/hypothesis that the dust short-circuited the battery migh thave
some merit.

Unless you have some rather highly conductive material in your dust,
it will not discharge a battery. You can test it easily by collecting
some of the dust out of the vacuum cleaner bag, and measuring its
conductivity with an ohms-guesser.

1. Dust caused short-circuit.

If your dust is full of iron filing, maybe. Otherwise, it's mostly
ground down dirt and whatever your carpet, drapes, and clothes are
made from. If your HVAC system is improperly sealed, some fiberglass.
If you live next to freeway, some finely ground rubber and soot. None
of these are sufficiently conductive to do anything to a battery.

2. Placing the battery I touched both sides reducing some of it's charge.

Take an ohms-guesser and measure the resistance between your fingers.
I just did mine and by pressing the probes really hard, I was able to
get it down to about 2Meg. With a common CR2032 cell of 3V, that's
1.5 microamps. The battery is rated at 225 ma-hrs. It would take:
225 ma-hr / 0.0015 ma = 150,000 hrs
to discharge the battery between your fingers.

3. I took the battery from another motherboard and it was already drained
somewhat.

Right. Two bad batteries make a good battery.

After cleaning I booted and booted again and I kinda noticed again checksum
failure or something.
So I think the battery is dead.

Try not to think too hard. Measuring is much easier. Morph your
ohms-guesser into a volts-guesser and measure the battery voltage. I
usually replace them below 2.9VDC.

After measuring the battery out of the motherboard, plug it in, and
measure it in the circuit. If there's a substantial drop in voltage,
you have a motherboard problem.

I've seen quite a few CR2032 sockets on motherboards, where someone
has tried to replace the battery and mangled the contacts. That was
extremely common with the older holders that had a contact arm over
the top. Todays don't have this arm, but rely on spring pressure from
below to make the connection. Check the spring.

Recently, I bought 50 no-name 2032 cells on eBay. They were all
garbage when I tested a few on a West Mtn Radio CBA-II analyzer.

So I have replaced the cmos/bios battery with a new one which I had lieing
around for a while.
It was still packed up so I am sure it's not used.
The battery is of the brand: VARTA
It has a date on it: july 2022.

Varta is a good brand and July 2022 is probably the expiration date.
It's likely to be a good battery.

For now I will consider this problem solved.

Congrats. Now, please go away.

Also there was quite a lot of dust inside the PC in hidden places... also
lot's of it in power supply... there might still be some.

Use an air compressor to blow it out. Ummm... do it outside.

I think in total it cost me 18:00 - 15:30 = 2 hours and 30 mins to clean
this sucker !

It takes me about 2-5 minutes to completely clean a PC with an air
compressor and a decent blow gun.
http://www.eastwood.com/5-piece-mini-blow-gun-set.html

I also cleaned the little motherboard fan with ear sticks... soap water, and
eventually oiled it.

Oiled it where? If on the surface, the oil will collect the dust and
produce a tar like goo that produce fan drag. Clean off the oil. If
you must oil the fan, peel off the label on the back side, inject ONE
drop of oil into the bushing, and put the label back.

The ammount of dust that came out of it is just amazing.

Like I mentioned previously, you're breathing that dust. Find the
source and clean it up.

Only the little fan was really dirty and needed new oil.

The small high RPM fans are a maintenance nightmare and have a very
short life. The ones in my security camera DVR and a few NAS boxes
need to be replaced about once a year. A post mortem shows that the
plastic around the center bushing is cracked from overheating.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558