'57 Zenith, finally openned the back

[jbivy]

Im a radio guy, so a total novice with these. Please bear with me.

Im going to try and figure out whats wrong (with help from an uncle who was a tv repairman int he late 60s and early 70s). She worked beautifully for fours hours, then i shut her off. When i powered it back up, the screen was just raster lines with an ocassional glimpse of the middle of the screen, showing in the bottom right.

And yes, i still cant find a sams for it.

[DaveWM]

Originally Posted by jbivy

nothing but static with the occasional glimpse of the picture (the center of the screen pic) in the bottom right.

I dont follow the description of the problem. Does it have a full raster?

[bandersen]

Originally Posted by jbivy

...And yes, i still cant find a sams for it...

What's the model / chassis # ? I have a stack of Sams, Riders, Wallace and Beitman service docs I can check.

[jbivy]

Well its a zenith royal and it says model z2251r on the back and the inside says chassis model 17z22.

Any idea on what i should concentrate on? Im about to pull the chassis and see if anything is apparent.

[DaveWM]

I still dont follow this

" just raster lines with an ocassional glimpse of the middle of the screen, showing in the bottom right"

[DaveWM]

if you just see snow then I would look to the RF tube in the tuner

If just raster with no snow then I would check the osc tubes thru the IF tubes

If the tube is blanked out I would check the video amp, and the agc/blanker tube (HV is present)

No HV check the horz out/damper/HV rectifier/horz osc

No sign of life at all check fuse/breaker shorted filter caps.

[jbivy]

Originally Posted by DaveWM

I still dont follow this

" just raster lines with an ocassional glimpse of the middle of the screen, showing in the bottom right"

If you think its safe for me to turn her on again, i can show a picture of it. Its just snow, with horizontal lines squiggling up and down about an inch, with the occasional picture in the bottom right of the screen.

[DaveWM]

yea I cant really form a mental pic of that, a real pic would be helpful.

I few things to check would be are the filter cans hot? not good. If they have a cardboard sleeve on them leave that on as it could be a doubler circuit in which case the can will have a high voltage potential and would be a shock hazard (thats why the cardboard is there).

If it has the orig filter caps then there is a good chance they could be open or shorted. same for any wax paper caps it may have.

a good test for overall health is a current reading of the B+ to see if its in spec, also a good idea to check the cathod current of the HOT to make sure its in spec so as not to stress out the flyback, which may be hard to get.

[Boobtubeman]

Check his second pic.. the purple sticker is the chassis #

Dont see a mod#

OOPS... chimed in late info given

[bandersen]

Here's a scan of the schematic from Most-Often-Needed "Early 1957"

http://www.bobandersen.com/images/sc...2schematic.jpg

It's covered in Riders Vol. 19 which I'm missing.