'57 Zenith, finally openned the back - Videokarma.org TV - Video

jbivy · #1 02-15-2011, 02:31 PM

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 · #2 02-15-2011, 02:35 PM

Quote:

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 · #3 02-15-2011, 03:03 PM

Quote:

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 · #4 02-15-2011, 03:48 PM

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.

Boobtubeman · #5 02-15-2011, 03:52 PM

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

Dont see a mod#

OOPS... chimed in late

info given

DaveWM · #6 02-15-2011, 03:53 PM

I still dont follow this

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

DaveWM · #7 02-15-2011, 03:56 PM

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 · #8 02-15-2011, 04:12 PM

Quote:

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.

bandersen · #9 02-15-2011, 04:15 PM

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.

DaveWM · #10 02-15-2011, 04:19 PM

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.

jbivy · #11 02-15-2011, 04:37 PM

Allright.. Now ive no picture whatsoever, the screen wont even light up. I havent turned it on in a few months, since the day it stopped working correctly.

I havent had a cigarette all day, now i think its time to light one up.

DaveWM · #12 02-15-2011, 05:12 PM

no filaments either?

DaveWM · #13 02-15-2011, 05:16 PM

if filaments are ok, then I would start by checking the B+ and the fuse in the damper circuit. My guess is the filter caps may be shorted, taking out the B+ maybe the 5u4 if the B+ is down anyway.

Phil Nelson · #14 02-15-2011, 08:16 PM

If it has the original 1957 electrolytics, there's about a 100% chance that they are shot. This article has basic info about recapping:

http://antiqueradio.org/recap.htm

I took a quick peek at the schematic and it appears you have two multi-section electrolytic cans: C40 and C14.

If you have worked on tube radios before, the same basic methods apply, only TVs are more complex and have high voltage.

After you have replaced those electrolytics, then it will make sense to troubleshoot specific symptoms.

Looks like a cool TV.

Phil Nelson
http://antiqueradio.org/index.html

marty59 · #15 02-15-2011, 10:02 PM

The whole chassis/bezel-CRT can be removed as an assembly through the front and kept intact for troubleshooting purposes. Remove the chassis screws where it attaches to the cabinet. This set is also covered in Howard Sams 343-18.

I have a model Z3000 that has the 17Z22Q/Space Command(er) chassis but I haven't done anything really intensive with it yet. One of the B+ caps is leaking so until I pull the chassis and fix the obvious it's going to have to wait awhile. I really like your cabinet design. Mine is a metal set with a faux blond wood finish that's not in the best of shape and sits on a pedastal with casters. At best, I would like to respray it in a close color and call it good, as well as refurbish the electronics..

The letters in the model number corrospond to the finish- E/blond, H/Cherry and R/Mahogany.

There is also another cap I'd be concerned with, and it ties between the B+ Boost and the B+. It is 10mfd 400V. Sams calls it a Non-Polar unit but Zenith does not make any special mention of it in their TV-17 manual as being such. Either way, that cap should be replaced too. Pull your chassis and see what kind it is. I'd bet you could use a standard electrolytic but if you ever lose B+ Boost then it could have a reverse polarity on it! You can make up a non-polar cap set-up by using two caps in series and tying the negatives together and using two 20ish mfd's.