Panasonic TV goes black

[Charlie Bress]

Panasonic CT-27G13

It may power up with audio and no picture just a black screen.
Audio is always good.
Repeated on-off-on sequence may bring up pic with normal video.
When it is turned off in these sequences, there is a quick flash on the
screen.
Sometimes when it is running it goes dark.
When this happens there is no sync loss or blooming.
It usually goes off as if switched off, it does not fade.
On one occasion when going black it seemed to go out in a few discrete steps
rather than a continuous fade.
A rap on the cabinet has had no effect.

What is going on here? What should I be looking for?

Bad solder joints are always an issue, but point me to the area of
suspicion.
I have resoldered joints in this box before and am familiar with the HV
concerns.
My problem is the unfamiliarity with the components in these sets.
Working with a printed ckt board is not a problem, only with what the
component line-up and description of stuff used in this vintage (1998) set.

Thanks
Charlie

 

[Shoreline Electronics]

When it goes black do you still get the on screen displays?

Try resoldering the vertical out IC.


--
==========================
Jeff Stielau
Shoreline Electronics Repair
344 East Main Street
Clinton,CT 06413
860-399-1861
860-664-3535 (fax)
[email protected]
========================

 

[[email protected]]

My guess is that it might be HV shutdown. Try running the set from a
variac, starting at about 85 -90 volts and see what happens. If the HV
is on the verge of triggering shutdown, minor, almost unobservable
changes in AC line voltage could trigger the overvoltage shutdown
circuit.

H. R.(Bob) Hofmann

 

[Charlie Bress]

No. the screen is completely blank. No raster at all.

Charlie

 

[Charlie Bress]

I thought about the loss of HV, but on the time that it went out in a couple
of steps as it dimmed down there was no blooming which I would thought would
have happened if the HV was degrading. If the HV had just triggered off I
would not think that the dimming would have occurred.

Charlie

 

[Shoreline Electronics]

Try resoldering the main power relay. All 4 pins


--
==========================
Jeff Stielau
Shoreline Electronics Repair
344 East Main Street
Clinton,CT 06413
860-399-1861
860-664-3535 (fax)
[email protected]
========================

 

[Vlad]

Panasonic CT-27G13

It may power up with audio and no picture just a black screen.
Audio is always good.
Repeated on-off-on sequence may bring up pic with normal video.
When it is turned off in these sequences, there is a quick flash on the
screen.
Sometimes when it is running it goes dark.
When this happens there is no sync loss or blooming.
It usually goes off as if switched off, it does not fade.
On one occasion when going black it seemed to go out in a few discrete steps
rather than a continuous fade.
A rap on the cabinet has had no effect.

What is going on here? What should I be looking for?

Bad solder joints are always an issue, but point me to the area of
suspicion.
I have resoldered joints in this box before and am familiar with the HV
concerns.
My problem is the unfamiliarity with the components in these sets.
Working with a printed ckt board is not a problem, only with what the
component line-up and description of stuff used in this vintage (1998) set.

Thanks
Charlie

Do you have high voltage when the screen is black?
Vlad

 

[Charlie Bress]

Do you have high voltage when the screen is black?
Vlad

I haven't opened the box up yet. This problem is intermittent enough that I
am waiting to see what responses I get here to have a plan of attack.
However, two symptoms lead me to believe it is not the HV
When the screen is black and you turn off the power there is a brief flash
of light on the screen. It seems there must be some potential to direct the
beam there.
And in the case where the screen dimmed down in a few discrete steps, there
was no blooming. I take this as an indication the HV is not degrading.

Charlie