1967 Zenith 24NC31Z roundie color tv

[consoleguy67]

Hi Everyone,

I'm new here to Videokarma. I have a 1967(1966) Zenith roundie tv. It has raster, but no actual picture or sound. It seems as if it is not getting any signal from the tuner. Where should I start looking to resolve this problem? Any assistance would be appreciated.


Thanks,
Frank

[miniman82]

Could be nearly anything, how are your electronics skills?

Pics please!

[DaveWM]

if its got no snow at all and no noise at all just a snow free blank raster, then I would check the osc tube in the tuner. But as mentioned it could be a lot of things, but for starters the tuner and the IF tubes would be a good place to start. Some times just wiggling tubes will bring it back to life as oxidation on the tube pins can interupt the circuits.

it really should be checked over for things like HOT current as leaky caps can cause damage to parts that are hard to replace. that being said, zeniths do hold up well and typically require minimum cap replacement.

[DaveWM]

pls post a pic, always nice to see the set in question.

[freakaftr8]

Wiggle the normal/service switch possibly?

[DaveWM]

good point esp if the serv switch has a 3 position (normal,grey scale,purity_

[Robert Grant]

Forgive me for raising the most obvious - If it is hooked to an antenna, not cable, VCR, or satellite dish, you will need an analog-to-digital converter box (do you find that some channels have brighter, thicker "snow"and lounder noise on some channels than others?

Next suspects would be the tubes in the tuner and in the IF strip (the little thin tunes in a line on the part of the chassis closest to the tuner).

A whole bunch of other things figure, countless caps, insufficient B+ due to a power supply problem (which could blow your whole project up!), even a video amp tube (can also knock out the sound).

I'm in the same boat as you (just acquired a Zenith roundie myself).

[Penthode]

I, too am curious. What is the signal applied to the antenna terminals?

[bgadow]

Zeniths do seem to need IF tubes quite often, probably because they've lasted so long as to wear them out. Could also be as simple as a dirty tuner. I've seen some that were totally blanked out by that.

[consoleguy67]

I've checked the tubes in the tuner, and they check OK. I have found some other bad tubes, and am waiting for them to come in. I will be posting pictures of the set soon. This is the set I have, The Barstow, as pictured in the sales brochure.

[DaveWM]

which tubes tested bad?

[consoleguy67]

As far as the signal, it is hooked up to digital cable, via a converter box, and also to a dvd player, via an rf convertor. I have a 1964 Magnavox stereo theatre(b&w) also hooked upto the same signal sources, and it plays great, so it's not an issue with the signal.

[consoleguy67]

I've also replaced the IF tubes (all three).

[DaveWM]

your video dvd should have a composite video out. I would try and connect that up at the output of the video detector diode (thru a .05 cap to be safe). This will clear the problem up thru the output of the video detector.

[consoleguy67]

Hi Dave,
Would that be the green lead comming out of the tuner? My knowledge is sort of basic.