Posted by Tom Moertel
Fri, 25 May 2007 21:42:00 GMT
The Kenwood audio-video receiver that forms the core of my
home theater system stopped responding to its remote control. As I
discovered shortly thereafter, having to leave the couch to fiddle
with knobs degrades the “home theater experience.” Clearly, something
had to be done.
I knew the receiver was the culprit because the remote control worked fine
with other components of my system. I figured the IR sensor had gone
bad and did a little Googling for “Kenwood” and “IR sensor” and
“problem”. The results revealed that
many other Kenwood customers had the same
problem.
The cause of the problem, I learned, was that the solder joints which
connect the IR sensor’s leads to the display board eventually fail
because of thermal expansion. That explanation seemed to account for
what I was observing, so I cracked the case in search
of visual confirmation.
First, I found the joints where the IR sensor was connected to the
circuit board. The vertical red line shows where I found them:
Then I examined the joints closely. Sure enough, at least one had completely failed:
The problem confirmed, I moved to the solution phase of the project.
With my soldering iron, I touched-up the joints:
It wasn’t my best work, but it did the job.
Now my receiver is back on speaking terms with its remote control,
and I have returned to the modern world. Life is good
Posted in hardware
Tags hardware, ir, kenwood, receiver, repairs, soldering
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Posted by Tom Moertel
Wed, 09 Aug 2006 04:35:00 GMT
If an extended power outage drains your UPS, and your servers are
forced to shut down, will they automatically start up again when the
power is eventually restored? It’s a good question, especially
if your servers are in some distant, unattended server room.
Unless you’ve tested your servers, don’t assume that the answer
is Yes.
Many servers offer a BIOS configuration option that forces them to
automatically power on when they receive line voltage. If your
servers have this option, just set it and you’re done.
Unfortunately, some servers, including a Dell PowerEdge 1600SC
that I’m using, lack this configuration option. When these servers
turn themselves off as the final step of a UPS-controlled
shutdown, they don’t start up again when the power is restored.
Because they were shut down before the power was cut off, they think
they are supposed to remain off when the power is restored. That is,
they remember their on/off status across power outages.
Fortunately, there is a way to make sure these servers automatically
power on: shut them down without powering them off; halt them
instead. That way, when the UPS finally cuts off the supply voltage,
the servers will still be in their “on” state, and they will remember
this state across the outage. Later, when the power is restored, the servers
will automatically restore their pre-outage state and power up.
With Fedora Core Linux and Network UPS
Tools, it’s not difficult to make
sure the servers are halted instead of powered off, but the implementation
isn’t obvious. To spare you the digging, here are the
important bits.
- When the power fails and the UPS-monitoring software decides that
the batteries are almost depleted, it will initiate a server shutdown
using the command defined in the
/etc/ups/upsmon.conf
file. The default command is this:
SHUTDOWNCMD "/sbin/shutdown -h +0"
- The shutdown command will tell the
init process
to enter runlevel 0, which is the prepare-to-halt-the-system runlevel.
- The
init process will stop all of the running
services in an orderly fashion, and then, as the last step, invoke the
final script in the shutdown process:
/etc/rc.d/rc0.d/S01halt.
- The final lines of the
S01halt script will
power off the server. Unless, that is, the file /halt is
present, in which case the script will halt the server instead.
Thus the trick is to make sure that the /halt
file does exist. The trick turns out to be easy to pull off;
just redefine the shutdown command in /etc/ups/upsmon.conf:
SHUTDOWNCMD "/bin/touch /halt; /sbin/shutdown -h +0"
And that’s all there is to it!
Posted in linux, hardware, sysadmin
Tags fedora, halt, hardware, linux, nut, power, shutdown, ups
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Posted by Tom Moertel
Sat, 12 Nov 2005 02:42:00 GMT
The main network switch in my home office is an HP ProCurve
4000m, which
has been running non-stop for over half a decade. It is a great
switch, and even though it is getting old, it is still dependable.
A while ago I noticed that the 4000m’s fault indicator was
lit. So I logged into the switch and checked the log: fan
1 was dead. The switch has built-in redundancy (three fans),
and so I didn’t worry about it, but I did call HP ProCurve
tech support.
The woman I spoke with was friendly and helpful. I told her what was
wrong, and she said a new fan array would
be on my doorstep within 48 hours. No charge. (I guess the
ProCurve warranty really is worth something.)
Today, I installed the array. This meant opening up the switch,
which is a fun thing to do. If you are curious about what is inside
of a 4000m, I took photos of the operation.
During the process, I recalled why I love old-style HP engineering:
- The replacement parts came with clear instructions
that showed me how to remove the old array and install the new one.
They were easy to follow and didn’t leave anything to guess.
- The 4000m is solid – inside and out.
- The electrical components are top quality.
- The industrial engineering is superb. For example, all of the user-removable
screws have non-stripping torx heads and are designed not to fall
out and get lost; instead they remain attached to the module or
panel you are removing. (See this photo of removed modules
to see how the screws stay in place.)
Everything about the process made me think, wow, this is really well engineered.
The thing is, I know, as I sit here and watch the blinking LEDs on my
now-restored 4000m, that my next network switch will probably be a
Dell.
As much as I love the ProCurve engineering, the Dell price is
compelling. Even if I expect the Dells to fail twice as often (and
the Dell warranties are comparatively lame), I can buy twice as
many Dells and keep spares on the shelf – and still save money
compared to the equivalent ProCurve equipment.
I find the situation somewhat sad. I am an engineering guy to the
core. So when I go for the cheaper product because it is so darn cheap,
I know that much of the market will do likewise. That bodes ill
for HP. Like HP’s calculators, the ProCurves too may pass into
history.
Posted in photography, hardware, engineering
Tags 4000m, engineering, hardware, hp, networking, photos, switch
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