Squiggly horizontal line walking up the CRT?

[Magnavox300]

My 1958 Admiral has one wavy horizontal line that starts at the bottom of the screen, and slowly moves up to the top, then repeats. It started back in the summer, but has seemed to have gotten worse.
Any Idea what is causing it?
Hard to get a photo of it, but I could try if needed.
Thanks...

[David Roper]

A hum bar? If the electrolytic caps are 54 years old they're due for replacement.

[Magnavox300]

Originally Posted by David Roper

A hum bar? If the electrolytic caps are 54 years old they're due for replacement.

Thanks, I actually replaced all the caps a few months ago.
What is a hum bar?

[Magnavox300]

Okay, just shut the set down, and I heard some humming from the speaker.
Now I know what you meant by "hum bar", I am guessing if there is any humming in the speaker, then that would cause a bar running up the CRT?
I shouldn't have hum after replacing the electrolytics, maybe there is a faulty one already.

[radiotvnut]

It's very possible that one of the new caps failed or you could possibly have a bad solder connection where the new caps are soldered in place. There could also be a bad ground connection somewhere or a heater-to-cathode short in a tube. The fact that it got worse over time leads me to think that a capacitor is failing.

[mstaton]

Hum bars are caused by AC voltage getting into the B+. It could be from a bad cap or a shorted filament in a tube(filaments are AC). The hum sound from the speaker is not causing the hum bar on the CRT. You are just hearing the 60 cycle hum through the audio circuit. Don't confuse audio hum and buzz, 2 different things. Buzz will change with the programming and hum will be constant. Yes a new cap can go bad.

Radiotvnut beat me to it!

[Magnavox300]

Originally Posted by mstaton

Hum bars are caused by AC voltage getting into the B+. It could be from a bad cap or a shorted filament in a tube(filaments are AC). The hum sound from the speaker is not causing the hum bar on the CRT. You are just hearing the 60 cycle hum through the audio circuit. Don't confuse audio hum and buzz, 2 different things. Buzz will change with the programming and hum will be constant. Yes a new cap can go bad.

Radiotvnut beat me to it!

Thanks,
I am sure it was a shorted filament in a tube, like you mentioned.
I had the brilliant idea of buying 14 NOS tubes from Ebay for this set a couple weeks ago. I thought with all NOS tubes in there, it would work even better than it already did!
They must not have been NOS, or at least some, cause ever since all I have had are problems.
Today, I put back all the original Admiral tubes one at a time, to test it, and after they were all in, it worked like new again!
I'm out 50 bucks on those tubes, though some may be okay, I really don't know.
I must get a tube tester already, it was foolish of me to gamble like that.
I did buy a Lafayette t-50 a month ago, but I could never get it to work.
I'll have to spend a little more and get something reliable already!

[Electronic M]

Always test tubes before installing them as even NOS tubes can have a percentage of lemons amongst them....Some tubes can only be completely tested in set, but a tube tester will still tell you which are too bad to bother putting in.