Admiral 19A1

[bigaudioal]

Working on this set a bit. Replaced a 100 pF cap in the vertical section and that helped the vertical linearity a bit. Need to test resistors in vertical section and replace as needed. Definite improvement though. See the below video. 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. Set is totally recapped now. Waiting for resistors to come in.

http://youtu.be/6ngQB28AaFA

Thanks!

[kramden66]

sometimes to get the linearity right on those you have to play around a little with the vertical coupling caps values , those 6kv caps.

are you certain your tuner tubes , if tubes and video tube are all ok ? you could try changing one at a time to see if it goes away , reminds me of tape drop out.

do you see those lines if you take one of the antenna terminals off making the picture weaker or with it just running without a signal ?

[Zenith26kc20]

It looks like arcing in the high voltage. These little sets are prone to arcing over around the CRT socket and the centering control area. Turn out the lights and make the room as dark as possible. Look for tiny sparks around the high voltage areas and if you can, slightly back off the CRT socket and look there also. Turning the brightness down usually won't make these arc worse. Dirt around the centering control terminals and case are a problem also. Also, look for light blue "streamers" (corona) arouns that area too. These can be a source also.

[Sandy G]

Still, overall, a pretty good picture/sound for one of these little guys...

[earlyfilm]

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.

[bigaudioal]

Thanks for these wonderful suggestions!!! I have the chassis out now and will try and locate this arching that you think is going on.

Thx.

[bigaudioal]

Update on my Admiral. I fired up the set last night after replacing another 10 resistors (have done about 30 so far) and the noise pulses (horiz. line flickering on the pic) was really bad. So with the set running, I tuned off all the lights and tilted up the set looking for arching - could not see anything. I turned the audio all the was down and could hear a very faint buzzing. The buzzing was a pulsing buzzing that seemed to correspond to the blanking. Sounding just like arching, but I could not see any arching. Seemed like it was coming from the area of the Horiz. sweep transformer, or between that and the 6kV caps. Then I saw the long red wire coming out of that transformer and wrapping around two of the 6kV caps. I took a plastic screwdriver and got that wire away from those 6kV caps and the buzzing sound and blanking stopped immediately. Re-routed the wire away from those caps and solved that issue. Now onto the vertical to see if I can solve the linearity issue, which has improved, but bottom of pic is still squashed. Here is a new video of where I am . . .

http://www.youtube.com/watch?v=Hk_5GgnBwNs

Thanks to everyone for the suggestions!!!! Really appreciate it.

[bigaudioal]

Back in the cabinet for now. My vertical output tube tests OK, not great. So that may be contributing to the vertical issue. Got to track down some 6SL7's. Otherwise pretty happy with result so far. Thanks to Tim (Kamakiri) for getting me going in this hobby and for all the hand holding. Having a blast and getting decent results so far.