I work on test equipment and experimental equipment a lot, and am familiar
with high-voltage precautions, but have not worked on a TV in 15 years.
Accordingly, let me ask...

The patient is a Magnavox 25-inch color TV from 1995. It went dead while in
use the other day (no one was watching at that exact moment) and now shows
absolutely no sign of power.

Where the AC power comes in, there is a tiny fuse, which is not blown, but
it's something like 1/10 amp and can't possibly be the main power inlet for
the TV. There is also an Omron relay or circuit breaker (at a quick glance
I couldn't tell which).

What should I be looking for/at?

Thanks...

"What should I be looking for/at? "

Standard tv troubleshooting:

Standby power supplies, system control and clock and data lines, on/off
control lines from system control, main power supply regualtor system,
horizontal start up, horizontal drivers, horizontal output, flyback.

Check for B+ voltage at collector of the horizontal output transistor
(mounted on large heat sink in the vacinity of flyback). If nothing
present, trace power supply backwards from collector. May be an open
pico fuse in this path. If you don't have voltage at secondary of B+
transformer, check the voltage regulator and standby supply as
suggested. A model # would help identify a possible common problem.

mc wrote:
I work on test equipment and experimental equipment a lot, and am familiar
with high-voltage precautions, but have not worked on a TV in 15 years.
Accordingly, let me ask...

The patient is a Magnavox 25-inch color TV from 1995. It went dead while in
use the other day (no one was watching at that exact moment) and now shows
absolutely no sign of power.

Where the AC power comes in, there is a tiny fuse, which is not blown, but
it's something like 1/10 amp and can't possibly be the main power inlet for
the TV. There is also an Omron relay or circuit breaker (at a quick glance
I couldn't tell which).

What should I be looking for/at?

Thanks...

Give us a model or chassis number. Fuse that small is probably
standby power supply, necessary but not usually the problem.


In article ,
ess says...
The patient is a Magnavox 25-inch color TV from 1995. It went dead while in
use the other day (no one was watching at that exact moment) and now shows
absolutely no sign of power.

Where the AC power comes in, there is a tiny fuse, which is not blown, but
it's something like 1/10 amp and can't possibly be the main power inlet for
the TV. There is also an Omron relay or circuit breaker (at a quick glance
I couldn't tell which).

I forgot, but check the main fuse (glass) for open. If open, perform a
diode test on the horizontal output transistor.

Check the capacitor in the main power rectification for undischarge
current.If so,the power supply is not funtioning,which you can check by
reading the 110..145v at the secondary supply....

"Ol' Duffer" wrote in message
...
Give us a model or chassis number. Fuse that small is probably
standby power supply, necessary but not usually the problem.

Magnavox 25CR12 C121. Thanks!

On Sun, 4 Dec 2005 11:05:15 -0500, "mc"
wrote:

I work on test equipment and experimental equipment a lot, and am familiar
with high-voltage precautions, but have not worked on a TV in 15 years.
Accordingly, let me ask...

The patient is a Magnavox 25-inch color TV from 1995. It went dead while in
use the other day (no one was watching at that exact moment) and now shows
absolutely no sign of power.

Where the AC power comes in, there is a tiny fuse, which is not blown, but
it's something like 1/10 amp and can't possibly be the main power inlet for
the TV. There is also an Omron relay or circuit breaker (at a quick glance
I couldn't tell which).

What should I be looking for/at?

Thanks...


Check the electrolytics near the B+ regulator. There was a common
chassis around that time that tended to lose a large cap there. I
think it also resulted in a shorted HOT.
Andy Cuffe

-- Use this address until 12/31/2005

-- Use this address after 12/31/2005

In article ,
ess says...
Magnavox 25CR12 C121. Thanks!

That model number does not compute for me, unless it is a
euro/asia model and I do not have access to that information.
Are you sure it isn't 25TR12?

If so, it could be an X6 chassis that may be subject to the
main B+ capacitor failure syndrome. 100uF 200V capacitor
goes open due to surge/thermal damage. Once open, the supply
loses regulation and climbs from its nominal 129V to something
more like 145V, which makes the horizontal output transistor
dissipate more heat. The HOT eventually shorts out, which
usually blows the 2.5A pico fuse, occaisionally damages other
stuff. The horizontal drive supply resistors also get hot
enough to burn off their printing and crystallize their solder
joints. I see these often enough to have it down to about a
half hour.

Other possibilities are B8 or P6 chassis which are switch mode,
run-all-the-time supplies that are much kinder to capacitors.