On Wed, 9 Dec 2009 23:41:31 -0800 (PST), Andrew VK3BFA
wrote:

On Nov 29, 10:50 am, "John R. Carroll" wrote:
Jim Wilkins wrote:
On Nov 28, 5:54 pm, Wes wrote:

Outside of a RF reciever, most televisions don't work the same as
they did when I was a kid.

They did go digital recently.

Downconvert, digitize, the rest is software.

I'd be interested in hearing about that.
I've gone from 30 decent channels to six poor ones.

--
John R. Carroll

Sorta correct - theres a large lot of electronics (digital) devoted to
getting the software decoded digital signal onto the screen, either
LCD or plasma. Has to map and address the screen in an X-Y plane -
most of this is build into the panel at manufacture, so replacement is
costly . With plasmas, its the high power/high voltage driver boards
that die, with LCD its the back light inverters....haven't had a
chance to pull one of the newer LED backlight panels to pieces yet....

The real issue with digital TV's is you cannot look at the screen and
get some idea of where the fault is, unlike analogue. They either
work, or they don't. No schematics available, fix by board
replacement. Totally uneconomic (except as a "interesting problem") to
reverse engineer to component level.

But thats true of most modern goods, except for Old Farts like us who
will spend a day machining a 10c part to fix a $20 machine....its not
economic, but we do it becaause it annoys the hell out of us that
"spare parts" is nowadays an oxymoron.

And back in the Old Days - why, I remember when I had to walk 10 miles
to school, barefoot, through the snow with nothing but a pointy stick
to protect myself from wolves. And this was after I had got up at 5am
to milk the cows and do my chores, breaking ice in the well to draw up
water for my mother. And if I hadn't taken a bundle of firewood with
me for the school heater, I was whipped and made to go out in a raging
blizzard and find some.....

And you tell the young people this, and they don't believe you.

Andrew VK3BFA.


You had me right up till the end - there's no wolves in Oz.

And they have a reason to not believe you when you get a critical
fact wrong, people start tugging on the other threads to find any
other loose ones - and soon the whole thing unravels. ;-)

Now then...

The Manufacturers of all electronics should be REQUIRED to release
full schematics into the public domain when the unit is out of
production and no longer supported, and the replacement circuit boards
are no longer available. Because old gear sometimes must be repaired
when there are no new replacements available for them, and you need
the old gear to read the old media.

When the museums and media conversion companies need to keep (for
example) old LaserDisc units, or 9-track computer tape drives, or
Colorado computer backup cart drives, or 4-track or 8-track carts, or
8" Floppies, or AMPEX 2" helical-scan videotape players, or 3/4"
open-reel videotape, or U-Matic or Betamax videotapes... And you are
fast running out of working units... THEN it pays to do component
level repairs.

And without the board schematics and the realignment procedures, and
the Super Seekrit conversion list of proprietary chip numbers to the
industry-standard chips they had relabeled, it can be almost
impossible to fix the unit - unless you were the engineer who built it
in the first place.

...AND you can remember what the hell you were thinking forty years
ago when you were building it, which can be the bigger problem.

-- Bruce --