Quote:
Originally Posted by bigaudioal
Can anyone identify the issue of the horizontal lines flashing up on the picture? Lines appear to be both black and white if you look close.
http://youtu.be/6ngQB28AaFA |
Well Al, I thought someone would pop up and give you a trouble shooting procedure for the black horizontal lines in your picture, but since no one else has, here goes:
In the US NTSC system, the maximum level amplitude modulated picture signal was black. This caused most reception noise to be black specks, which were less visible than they would have been if the noise showed as white.
What you are seeing are electrical noise pulses. These are not short spikes like most noise, but relatively long pulses. There is a white trailing edge. This could from a poorly filtered high voltage supply, or much more likely the IF and Video tubes take time to recover.
This can be caused by a difference in chassis potential between the TV and your signal source.
(Yes, I know your set has a 100% isolated power transformer, but the insulation could be breaking down.)
I'd connect the signal source to an old rabbit ears and the TV to a second rabbit ears a few inches away from the other. See if that removes the black lines.
On a magnetically deflected set, the first place I'd look is the horizontal output and high voltage transformer and CRT area.
However, the 19A1 is a electrostatically deflected set, so the HV is relative modest, but I'd still give a look see in a dark room and see if you can see any arcing. Then take a cardboard tube, or a plastic hose, and listen for any popping in the HV area that seems to match the picture streaks.
Next take a wooden dowel and gently thump all the tubes and see if any created the black lines.
If at this point, if you still have not located the problem, the fun begins!
Since this set has been recapped, do a complete visual inspection of all new shiny soldered joints looking for a cold soldered connection.
The most probable causes left are: Something is arcing or breaking down, and it most probably is a resistor or potentiometer. Next in probability is a transformer.
Measure the three resistors in the 6V6 H.V. Oscillator, as these are a prime suspect as this is probably the most power handling tube in the set.
Take a scope and follow the video signal from the CRT back through the video and the video IF or until the random peaks in the sync area disappear, then check all components at this point.
(But, you say, it could not be in the IF, because then it would also be in the sound. Wrong, because the sound is FM.)
I assume that this is the same set that Kamakiri was working on a few threads back in his "No vertical" thread. If so, I can see the same streaks that you pointed out were also showing in his last youtube post at:
http://www.youtube.com/watch?v=wWhXO...ature=youtu.be
Since the problem seems to be worse when the set warms up, you may have to wait longer when the chassis is out of the cabinet for the problem to appear.
Jas.