TV startup problem
 

My sister inlaw gave me her non-working 27" TV and
I'd like to get it going to replace my smaller one.

It's a(n) MTC (manufacturer) model: MTV-2800S

A button is pressed to, I guess, turn on the unit maybe
to precharge the picuture tube and then another button
is pressed to actually turn it on and off. A little red LED
comes on, on the front, when the first button is pressed.

When the second button is pressed (after being turned off
for awhile) I hear a thunk from the internal speakers and what
sounds like static from the picture tube firing up..... but then
nothing. No picture, no sound and the filaments on the ass
end of the picture tube don't light up and the speakers make
a sound like it's lost power. The little red LED on the front
stays lit.

That only happens when first turned on after being off for awhile.

I'm told that if I turn it off and on about 100 times it might actually
come on and stay on. I've yet to confirm that.

Should I search for a problem in the power supply I wonder?
I'm a home-electronic-fix-it-for-myself-kinda-guy. Any advice,
help, or suggestions would be greatly appreciated.

Thanks, loads.

- Chris

TV startup problem
 

Call me stupid (hey, stupid!) ---
two fuses in the power supply?!
One in the front part, easily seen...
one in the back, kinda buried...
and .... blown.

Replaced it. Turned TV on. It held.
Now I'm hearing a whine or a shrill
or a buzz coming from the area of the
large transformer in the power supply.

I think (correct me if I'm wrong) that
it isn't an indication of a failure in that
transformer but rather maybe an electrolytic
somewhere in the power supply circuit?

- Chris

TV startup problem
 

depends on what transformer you are talking about ?
if your referring to an upper class tv with a
switching supply then you may have a short.
normally a bad E-Cap in the power section throws
the over load how ever, you could have a bad
flyback circuit. (Transistor,Coil,Rectifier etc).


Fannie wrote:

Call me stupid (hey, stupid!) ---
two fuses in the power supply?!
One in the front part, easily seen...
one in the back, kinda buried...
and .... blown.

Replaced it. Turned TV on. It held.
Now I'm hearing a whine or a shrill
or a buzz coming from the area of the
large transformer in the power supply.

I think (correct me if I'm wrong) that
it isn't an indication of a failure in that
transformer but rather maybe an electrolytic
somewhere in the power supply circuit?

- Chris

TV startup problem
 

I'm leaning towards a bad E-Cap in the power section.
Without a schematic I'm pulling the largest ones and/or
testing/replacing. The whole power supply section seems
to be on its own removable PC board so I (guess) I will
stay on that part and concentrate the E-Cap search.

Fingers crossed hoping it's that simple. LOL

- Chris

"Jamie" wrote in message
...
depends on what transformer you are talking about ?
if your referring to an upper class tv with a
switching supply then you may have a short.
normally a bad E-Cap in the power section throws
the over load how ever, you could have a bad
flyback circuit. (Transistor,Coil,Rectifier etc).


Fannie wrote:

Call me stupid (hey, stupid!) ---
two fuses in the power supply?!
One in the front part, easily seen...
one in the back, kinda buried...
and .... blown.

Replaced it. Turned TV on. It held.
Now I'm hearing a whine or a shrill
or a buzz coming from the area of the
large transformer in the power supply.

I think (correct me if I'm wrong) that
it isn't an indication of a failure in that
transformer but rather maybe an electrolytic
somewhere in the power supply circuit?

- Chris

TV startup problem
 

If you change the E-cap and it still does not work, check the circuit that
drive the switching transistor.
Check the diodes and caps.


"Fannie" wrote in message
...
I'm leaning towards a bad E-Cap in the power section.
Without a schematic I'm pulling the largest ones and/or
testing/replacing. The whole power supply section seems
to be on its own removable PC board so I (guess) I will
stay on that part and concentrate the E-Cap search.

Fingers crossed hoping it's that simple. LOL

- Chris

"Jamie" wrote in message
...
depends on what transformer you are talking about ?
if your referring to an upper class tv with a
switching supply then you may have a short.
normally a bad E-Cap in the power section throws
the over load how ever, you could have a bad
flyback circuit. (Transistor,Coil,Rectifier etc).


Fannie wrote:

Call me stupid (hey, stupid!) ---
two fuses in the power supply?!
One in the front part, easily seen...
one in the back, kinda buried...
and .... blown.

Replaced it. Turned TV on. It held.
Now I'm hearing a whine or a shrill
or a buzz coming from the area of the
large transformer in the power supply.

I think (correct me if I'm wrong) that
it isn't an indication of a failure in that
transformer but rather maybe an electrolytic
somewhere in the power supply circuit?

- Chris

TV startup problem
 

Have changed the E-Cap and it has not fixed.
In-circuit check of diodes seem fine.
All large caps have been checked/replaced.

Am now moving on to switching transistor circuit.
Can't be much else left. :-)

Despite the squeeling transformer in the power supply
and the front LED lighting up... there's little or no heat
being generated from much of the power supply
circuitry. Even those large stone resistors are cold.

I'm about to check the high current switch transistor
and regulator transistor. I'll post the findings.

-Chris

"Arif Witjaksono" wrote in message
...
If you change the E-cap and it still does not work, check the circuit that
drive the switching transistor.
Check the diodes and caps.


"Fannie" wrote in message
...
I'm leaning towards a bad E-Cap in the power section.
Without a schematic I'm pulling the largest ones and/or
testing/replacing. The whole power supply section seems
to be on its own removable PC board so I (guess) I will
stay on that part and concentrate the E-Cap search.

Fingers crossed hoping it's that simple. LOL

- Chris

"Jamie" wrote in message
...
depends on what transformer you are talking about ?
if your referring to an upper class tv with a
switching supply then you may have a short.
normally a bad E-Cap in the power section throws
the over load how ever, you could have a bad
flyback circuit. (Transistor,Coil,Rectifier etc).


Fannie wrote:

Call me stupid (hey, stupid!) ---
two fuses in the power supply?!
One in the front part, easily seen...
one in the back, kinda buried...
and .... blown.

Replaced it. Turned TV on. It held.
Now I'm hearing a whine or a shrill
or a buzz coming from the area of the
large transformer in the power supply.

I think (correct me if I'm wrong) that
it isn't an indication of a failure in that
transformer but rather maybe an electrolytic
somewhere in the power supply circuit?

- Chris

TV startup problem
 

When you testing the diode, it is better to it take off. I had experiance
when I tried to fix my freind's telly. I check the diode in-circuit and
found it seems ok, but actually it was open circuit. The diode was used to
start / give power to the switching circuit.

If you have CRO, check the base of the switching transistor. Usually
squeeling tranformer happens because:
a. switching frequency is wrong
b. the switching circuit try to start itself but fail, due to incorrect
starting voltage.

Good luck !

"Fannie" wrote in message
...
Have changed the E-Cap and it has not fixed.
In-circuit check of diodes seem fine.
All large caps have been checked/replaced.

Am now moving on to switching transistor circuit.
Can't be much else left. :-)

Despite the squeeling transformer in the power supply
and the front LED lighting up... there's little or no heat
being generated from much of the power supply
circuitry. Even those large stone resistors are cold.

I'm about to check the high current switch transistor
and regulator transistor. I'll post the findings.

-Chris

"Arif Witjaksono" wrote in message
...
If you change the E-cap and it still does not work, check the circuit
that
drive the switching transistor.
Check the diodes and caps.


"Fannie" wrote in message
...
I'm leaning towards a bad E-Cap in the power section.
Without a schematic I'm pulling the largest ones and/or
testing/replacing. The whole power supply section seems
to be on its own removable PC board so I (guess) I will
stay on that part and concentrate the E-Cap search.

Fingers crossed hoping it's that simple. LOL

- Chris

"Jamie" wrote in
message
...
depends on what transformer you are talking about ?
if your referring to an upper class tv with a
switching supply then you may have a short.
normally a bad E-Cap in the power section throws
the over load how ever, you could have a bad
flyback circuit. (Transistor,Coil,Rectifier etc).


Fannie wrote:

Call me stupid (hey, stupid!) ---
two fuses in the power supply?!
One in the front part, easily seen...
one in the back, kinda buried...
and .... blown.

Replaced it. Turned TV on. It held.
Now I'm hearing a whine or a shrill
or a buzz coming from the area of the
large transformer in the power supply.

I think (correct me if I'm wrong) that
it isn't an indication of a failure in that
transformer but rather maybe an electrolytic
somewhere in the power supply circuit?

- Chris

TV startup problem
 

Very probable excessive load on the SMPS such as a shorted horizontal
output, bad LOPT, Etc..
"Arif Witjaksono" wrote in message
...
When you testing the diode, it is better to it take off. I had experiance
when I tried to fix my freind's telly. I check the diode in-circuit and
found it seems ok, but actually it was open circuit. The diode was used to
start / give power to the switching circuit.

If you have CRO, check the base of the switching transistor. Usually
squeeling tranformer happens because:
a. switching frequency is wrong
b. the switching circuit try to start itself but fail, due to incorrect
starting voltage.

Good luck !

"Fannie" wrote in message
...
Have changed the E-Cap and it has not fixed.
In-circuit check of diodes seem fine.
All large caps have been checked/replaced.

Am now moving on to switching transistor circuit.
Can't be much else left. :-)

Despite the squeeling transformer in the power supply
and the front LED lighting up... there's little or no heat
being generated from much of the power supply
circuitry. Even those large stone resistors are cold.

I'm about to check the high current switch transistor
and regulator transistor. I'll post the findings.

-Chris

"Arif Witjaksono" wrote in message
...
If you change the E-cap and it still does not work, check the circuit
that
drive the switching transistor.
Check the diodes and caps.


"Fannie" wrote in message
...
I'm leaning towards a bad E-Cap in the power section.
Without a schematic I'm pulling the largest ones and/or
testing/replacing. The whole power supply section seems
to be on its own removable PC board so I (guess) I will
stay on that part and concentrate the E-Cap search.

Fingers crossed hoping it's that simple. LOL

- Chris

"Jamie" wrote in
message
...
depends on what transformer you are talking about ?
if your referring to an upper class tv with a
switching supply then you may have a short.
normally a bad E-Cap in the power section throws
the over load how ever, you could have a bad
flyback circuit. (Transistor,Coil,Rectifier etc).


Fannie wrote:

Call me stupid (hey, stupid!) ---
two fuses in the power supply?!
One in the front part, easily seen...
one in the back, kinda buried...
and .... blown.

Replaced it. Turned TV on. It held.
Now I'm hearing a whine or a shrill
or a buzz coming from the area of the
large transformer in the power supply.

I think (correct me if I'm wrong) that
it isn't an indication of a failure in that
transformer but rather maybe an electrolytic
somewhere in the power supply circuit?

- Chris

TV startup problem
 

Yes, that's what it appears to be. There indeed is a short in
the HOT. I'm waiting now to pick up a replacement transistor.
It sure is gonna be nice to get this TV up and running. ;-)

"Art" wrote in message
...
Very probable excessive load on the SMPS such as a shorted horizontal
output, bad LOPT, Etc..
"Arif Witjaksono" wrote in message
...
When you testing the diode, it is better to it take off. I had
experiance
when I tried to fix my freind's telly. I check the diode in-circuit and
found it seems ok, but actually it was open circuit. The diode was used
to
start / give power to the switching circuit.

If you have CRO, check the base of the switching transistor. Usually
squeeling tranformer happens because:
a. switching frequency is wrong
b. the switching circuit try to start itself but fail, due to incorrect
starting voltage.

Good luck !

"Fannie" wrote in message
...
Have changed the E-Cap and it has not fixed.
In-circuit check of diodes seem fine.
All large caps have been checked/replaced.

Am now moving on to switching transistor circuit.
Can't be much else left. :-)

Despite the squeeling transformer in the power supply
and the front LED lighting up... there's little or no heat
being generated from much of the power supply
circuitry. Even those large stone resistors are cold.

I'm about to check the high current switch transistor
and regulator transistor. I'll post the findings.

-Chris

"Arif Witjaksono" wrote in message
...
If you change the E-cap and it still does not work, check the
circuit
that
drive the switching transistor.
Check the diodes and caps.


"Fannie" wrote in message
...
I'm leaning towards a bad E-Cap in the power section.
Without a schematic I'm pulling the largest ones and/or
testing/replacing. The whole power supply section seems
to be on its own removable PC board so I (guess) I will
stay on that part and concentrate the E-Cap search.

Fingers crossed hoping it's that simple. LOL

- Chris

"Jamie" wrote in
message
...
depends on what transformer you are talking about ?
if your referring to an upper class tv with a
switching supply then you may have a short.
normally a bad E-Cap in the power section throws
the over load how ever, you could have a bad
flyback circuit. (Transistor,Coil,Rectifier etc).


Fannie wrote:

Call me stupid (hey, stupid!) ---
two fuses in the power supply?!
One in the front part, easily seen...
one in the back, kinda buried...
and .... blown.

Replaced it. Turned TV on. It held.
Now I'm hearing a whine or a shrill
or a buzz coming from the area of the
large transformer in the power supply.

I think (correct me if I'm wrong) that
it isn't an indication of a failure in that
transformer but rather maybe an electrolytic
somewhere in the power supply circuit?

- Chris

TV startup problem
 

Before you replace the HOT find out why it blew.

kip