Monday, February 27, 2012

Going Crackers

I like to be economical whenever practical.  For example, I refuse to buy a packet of crackers out of a vending machine at work.  Those things cost about 60 cents a pop, and it's only six crackers.  Why do that, when I can buy a box of 36 cracker packs from Sam's for $7.52?  That works out to 21 cents a pack, a savings of over $14 compared to the vending machine price.

Yes, I know, I could save even more if I bought a big box of crackers and put a few into zip-lock sandwich bags.  Or save even more by being healthy and not eating processed crackers in the first place.

But I like the convenience of cracker packs.  I can grab a handful at a time, stuff them into my computer bag for the drive into town, and stow them in a desk drawer for future consumption.

That was the situation this morning.  I collected up about nine crackers packs and plopped them down beside me on my home desk, then turned to the office laptop for a quick check on email before shutting down and joining parking lot that is called "commuting" in Atlanta.

That's when my son came downstairs.  He's taking classes at Georgia Tech, and we carpool together to use the diamond lane.  He spies my booty pile of crackers, cocks his eyebrow like Mister Spock and just looks at me inquisitively.

Time for defense!  I went into Cat Mode™, placed my hand gently over the booty and said, "Mine!"

"Hungry much?" he replied, and began to reach tentatively in the direction of my crackers; not seriously, but only because I was acting protective.

"Not really," I replied.  "I plan to pace myself and eat these over a span of five minutes."

That got a laugh, and I no longer had to defend my booty.  I packed away the laptop and crackers, grabbed my coffee, and off we went.

"Went" is a relative term.  First we had to run the gauntlet of three schools to get to the main highway, and from there to Interstate 75 southbound.  The schools weren't a problem; the real trouble began on the approach to the freeway entrance.  We spent maybe 15-20 minutes in line just to turn onto the entrance ramp, and it didn't get any better.  Six lanes of southbound traffic creeping along.

We finally came across the problem.  An 18-wheeler rig had jackknifed off the road, sweeping along at least two cars and a van into the ditch.  Never mind at this point only the rightmost lane was blocked -- EVERYONE in the other five lanes crawled by slowly so they could all get a good look.

If that doesn't drive you crackers, I don't know what will.

Sunday, February 26, 2012

Home TV Repair, Part III

Back from the store, I spread out newspaper on the dining room table and plugged in the soldering iron.  The first step was "tinning" the tip of the iron, which means melting a bit of solder onto the tip and coating it with solder.  This keeps the tip from rusting and makes it easier to solder.

Next, I took a look at the power supply board, flipping it front to back until I could determine which solder points on the back side were the ones belonging to the two bad capacitors.  I marked the points with a sharpie pen, then laid down the board upside-down.

Now it was time to do a little de-soldering, something I hadn't tried in decades, and never on an electronics board.

I can tell you the little de-soldering bulb, well, sucks.  You use the iron to heat up and melt the existing solder, in your other hand squeeze the bulb, place the bulb tip as close to the melted solder as possible - even touching - then quickly release the bulb so it will slurp up the old solder.

Okay, it wasn't really the bulb's fault. :) I was having trouble keeping my hand steady while rapidly releasing the bulb.  I did finally get the solder slurped up, but it took some practice.

If I ever have to do this again, I think I'll try a "vacuum desoldering tool," which is basically a spring-loaded solder sucker.  You cock it, point it at the solder to be removed, and press the trigger.  Bingo!  Solder gone.

With the solder gone, I turned the board over and removed the two bad capacitors.  And I was lucky -- sure enough, the two old capacitors were 1000 microfarads each, just like the ones I had bought.  But there were two differences:
  1. The old capacitors were 25-volt; the new ones 35-volt, and slightly larger in diameter.
  2. The old capacitors were black, and had a higher heat rating, good to 105 centigrade.  I didn't recall seeing anything like that in stock at the electronics store.  The ones I bought were blue, and rated to 85 centigrade.
From everything I could gather, replacing the old capacitors with higher voltage ones was not a bad thing -- perhaps superior to the originals.  I was concerned about the heat rating, but finally rationalized it to myself that perhaps a higher voltage/slightly bigger capacitor would not run as hot as the old ones.  Besides, I didn't want to have to special order capacitors off the Internet and wait days for delivery.  So, right or wrong, I installed the capacitors I had.

This is where I expect to hear from someone who knows this stuff.

Putting in new capacitors is just a matter of sticking the wires through the holes, then bending them in opposite directions to hold the capacitors seated in place.  The important part is to make sure you put them in the right way:  positive wire through the positive hole; negative wire in the negative hole.  Both capacitors and the board are marked.

Once in place, just turn the board over, and you can solder the capacitors.  With the iron, touch the wire at the board, wait a couple of seconds, then touch the solder to the hot wire.  The solder should melt pretty quickly, filling the hole.

It only takes a very small amount of solder.  In fact, I overdid the first one with a large blob, then used less solder for the remaining holes.  After inspecting my work, I decided I needed to redo the first over-sized blob for fear it might make contact with something nearby.  I de-soldered it, and tried again, and got looking like the other solder points.

After that, it's matter of clipping the excess wire from the capacitors, and reinstalling the power supply board.

After putting everything back together, with much anticipation of smoke and fireworks, I plugged the TV back in.  Nothing bad happened.  I picked up the remote control and hit the power button.  The TV turned on normally!  Yeah, my home repair worked!!!

At this point, my only lingering concern is the heat rating on the capacitors.  Did I do the equivalent of replacing a flat tire with space-saver tire?  Something that will work for the time being, but really should be replaced?

Well, at least I know I can replace capacitors successfully.  If the TV breaks down again, I'll buy the right temperature-rated capacitors for the next round.  As I now own a soldering kit, that makes the next repair even cheaper; just the cost of the capacitors themselves, about $4 or so.
Home TV Repair, Part II

Braced with knowledge gained from YouTube, I was now going to attempt my own TV repair.

The first trick was to remove the support stand. I unplugged everything from the TV, set it upside-down on the den rug, held it between my knees, removed three screws from the base of the support stand, and it lifted right off.  Okay, so far so good.

I gently laid the TV face down and examined the back, ignoring the "No serviceable components inside.  To be open by trained personnel only" message.  Most obvious were the four mounting screws in back.  Those came out.  Next were the screws along the edge of the back.  I could see something like 17 screws around the border.  Many were in deep "wells."  Without a magnetized screwdriver, there's no way I could completely remove the screws, but I could at least unscrew them, and they should not present a problem when I lifted the back off.

Tip:  I grabbed a couple of zip-lock sandwich bags from the kitchen to keep the screws organized.  Last thing I needed was for one of the cats to come along and start batting loose screws off the coffee table.

17 screws unscrewed later, I tried lifting the back off the TV, and it wouldn't come up.  Then I noticed an 18th screw near the component plugs.  I removed that, and it still wouldn't lift off.  Wow, a 19th screw was hiding between two plugs in back.  Easy to miss.  And the back still wouldn't lift off.  Then I noticed the VGA plug with its two hex-shaped screws.  I removed them, and AT LAST, the back easily lifted off.

Lesson learned:  If the back of your TV is resisting removal, don't try to force it -- look for more screws, in particular in and around the various plugs in back.

Now I was looking at a metal cage covering the motherboards.  More screws to remove the cage, and a couple of things to unplug to get the cage loose.  That done, I was now looking at two motherboards.  One was the power supply board, and the other the CPU board.  The power supply board was identifiable by looking a bit more "primitive" with resistors, some possible transistors (are they still made?) and, in particular, capacitors sticking up.

Sure enough, I could see two small capacitors were bulging on top.  The rest look flat.  There were several ribbon cords with different connectors attached to the power supply board.  Just to be sure, I photographed the board, then unplugged everything, and removed still more screws holding the board in place.  The board lifted up easily.

Tip:  If you have curious pets, cover the TV with the back to keep pets out.  I also repositioned the cage, and put the zip-locked screw bags in prior to covering to keep our cats out.  (Or, I could have just shut the door to the den.  Yeah, that would have worked too.)

With a closer look at the power supply board in better light, I still could not make out the writing on the capacitors while still they were still mounted.  I would have to remove then to read them, but I did recall in one of the better YouTube videos, the guy mentioning the capacitors he replaced as being 1000 microfarads (µf).

I headed off to Radio Shack an electronics store to buy a soldering iron and supplies.  I wound up selecting a solder kit with a 30-watt soldering iron, plus some basic tools like small needle-nose pliers, diagonal cutters, solder, etc.  In addition I purchased a de-soldering bulb (basically a little rubber bulb you use to suck up old, melted solder) and a tin of flux, which in hindsight I probably didn't need.  On speculation I also grabbed two 1000 microfarad capacitors just in case that's what I needed.

Total purchase:  $32, and that was largely for the solder kit and supplies.  The capacitors themselves were $1.70 each.

Next up:  The replacement

Home TV Repair, Part I

Got a flat screen HDTV in your home?  These days, almost everyone seems to.  There's just one problem:  Unlike the CRT TV's of old, HDTV's simply don't last very long -- maybe 5 years at best before something goes wrong.

This has happened to me now.  My nearly 4 year old Samsung started to cycle on and off when attempting to turn it on.  If we left it alone, eventually, after maybe 5 minutes, it would finally turn on and stay on.  Then 5 minutes became 10, became 15....  One day I came home from work about 6PM, and I noticed the TV cycling on and off.  I asked my wife, "What time did you turn on the TV?"

"About noon," was the reply.

"You left the TV to cycle for 6 hours?  I think it's safe to say it's not going to turn on."

"Well, it won't turn off."

"Unplug it."

"I can't reach the plug."

Sighing, I went into the den and unplugged the thing.  At this point, I figured the TV was a loss.  It was well past warranty, and I did not purchase an extended warranty because extended warranties are usually a waste of money.  I could well imagine a service call would cost nearly as much as simply buying a new TV.

Then I starting doing a little research Googling the symptoms, and discovered:
  1. This is a common problem with Samsung TVs.
  2. The cause is one or more capacitors on the power supply board going bad.
  3. This is not just a Samsung thing.  In general with modern electronics, if something goes wrong, it is usually a bad capacitor.
  4. Capacitors are dirt cheap and readily available at electronics supply stores.
Then I looked on YouTube and found multiple instructions on how to replace capacitors on a mother board.  I used to do a bit of soldering when I was a kid, I thought.  How hard can it be to try doing my own repair?  Worst case:  I screw it up and need to buy a new TV.  Big deal, I'm already facing that now.  Surely it's worth a shot....

Next up:  The big unscrewing