|
|
|
|
|
#1
12-25-2013, 04:51 PM
|
||||
|
||||
|
Zenith Advanced System 3 picture tube testing
I was hoping to test the picture tube in my moms Zenith Model SS2721H. This set was manufactured in June of 1991. The CRT is listed as a GA68ACT00X. My Sencore CR70 setup book dated 1992 does not list this CRT? I was told 12 years ago that these had junk CRT's, but I never figured out what exactly was causing the original problem of green retrace lines in the picture. We suspected it was a heater to cathode short, but I never had a good way to test it back then. Now 12 years later the set won't even power on unless I unplug the PC board that plugs onto the CRT base. My mom is still attached to the cabinet of this set. Guess I could put a flat screen in there for her.
Last edited by Kevin Kuehn; 12-25-2013 at 04:57 PM. 
|
|
#2
12-25-2013, 06:37 PM
|
||||
|
||||
|
To test the jug use the universal adapter & the "common"
settings ( dont remember what they were). Green & retrace could be H-GK short, tap neck wile running & see if it flashes. Can also hang a meter on GK & pull socket while running. Normal K voltage abt 100V - 130V, if low with socket on but normal off its the tube. Set can shut down with excessive beam current BUT it must warm up 1st. Can be caused by: Excessive G2 voltage loss of 200 V supply for the R,G, & B transistors. A dead shorted H-K may also. Sometimes these sets would come in with the power supply out. Fixed them, looked OK then a few weeks later back again. The CRT's arced & blew the supply. Most I saw bad were from low emission or drifting grey scale followed by shorts & arcs. It also affected cheap models more so I would guess they put a better grade in the high end sets ( they deny that). 73 Zeno 
|
|
#3
12-26-2013, 10:30 AM
|
||||
|
||||
|
Quote:
|
|
#4
12-27-2013, 07:39 AM
|
||||
|
||||
|
You can usually see the filament pins then trace out the others.
Just put the 2 F clips on first & be sure it lights before going on. Here is the pinout for a mid 80's Zenith 27" jug. Odds are its the same. F pin 9 F 10 KR 8 KB 11 KG 6 G-1 5 G-2 7 Focus 1 After I wake up I will see if I got a manual  73 Zeno
|
|
#6
12-27-2013, 10:53 PM
|
||||
|
||||
|
I went over to moms tonight with my CR 70 in hand. I think I figured out the CRT pinout, and it actually seemed like all three guns checked OK for HK shorts. Cutoff and emission seems OK too. Took a few pictures of the set.
 What's the little slide switch on the CRT PC board for, possibly setup?   I finally got the set to come on with the CRT board plugged in. This is with no input signal. Normal background hiss with the volume up.  These next three pictures are with a DVD Player hooked to a A/V inputs. I can see a vague image moving around accompanied by a loud hissing-scratching- popping sound from the speakers, with the volume all the way down. It almost seems like the video is modulating the audio power supply. Anyone recognize these symptoms? This is not what I remember this set doing 12 years ago when I had it on. But my folks had two of these same sets(one upstairs, one down), so it's possible I was working with the other one at the time.    I'm about to drag this set up out of moms basement and back to my place. It's a real pain trouble shooting it over there away from my shop. If nothing else it needs to come out of there so I can dispose of it. But it sure would be nice to get to the bottom of this problem before sending if off to the recyclers. 
|
|
#9
01-18-2014, 11:36 PM
|
||||
|
||||
|
Good job fixing that television you saved it from the scrap yard . That's always good when People care to fix a television and not buy that Chinese flat panel junk that breaks after 3 years or right after the warranty from the manufacturer .I always thought Zenith was a very High End set , But I also Like Sony Trinitrons Televisions . I got A 40 Inch set for free from a guy in Waukegan .Illinois that Didn't want to fix it . I need the famous Mz3001d chips in her . But the set is working Not and has been turning on and not giving me any trouble knock on wood .I have the chips and if needed I can replace them now .
|
|
#10
01-23-2014, 09:30 PM
|
||||
|
||||
|
I've started to notice some light-dark horizontal streaking in the picture. Also some light green retrace lines are visible when the set is first turned on, as well as the screen collapses to a green dot when powered down. So it seems there may be some heater to cathode leakage after all. So far I haven't been able to capture the green retrace lines on camera, only the light-dark streaks. What do you guys think?
 
|
| Audiokarma |
|
#11
01-24-2014, 04:29 AM
|
||||
|
||||
|
You have directv hooked up to it . My Sony television will do the same thing too . Try a dvd player and see how the picture is . Im betting it one of your coax cables causing that bad picture or something in the tuner getting the signal . Check your cables
|
|
#12
01-24-2014, 07:32 AM
|
||||
|
||||
|
Actually it is a DVD player with separate RCA audio and video cables hooked to the TV.
|
|
#13
01-24-2014, 08:04 AM
|
||||
|
||||
|
An odd symptom. If it comes & goes try light tapping
of the CRT neck & see if it flashes. Can also swap the transistors around & see what happens. Also run your tester up a little on the filaments & see if it smokes out leakage. Try it at 8V. These sets did some strange things when the CRT's were bad............. 73 Zeno
|
|
#14
01-24-2014, 01:16 PM
|
||||
|
||||
|
Whatever it is it likes to manifest itself on mostly light blue screens. The moire effect makes it a little tough to see below. The color rendering looks great to me. I'll try testing the CRT again later.
 
Last edited by Kevin Kuehn; 01-25-2014 at 01:09 AM.
|
|
#15
01-24-2014, 02:21 PM
|
||||
|
||||
|
More pictures...
http://i452.photobucket.com/albums/q...ps91760968.jpg http://i452.photobucket.com/albums/q...ps178f8654.jpg http://i452.photobucket.com/albums/q...ps505032fb.jpg http://i452.photobucket.com/albums/q...ps814fa621.jpg http://i452.photobucket.com/albums/q...ps15b27b4a.jpg http://i452.photobucket.com/albums/q...ps4ac0770b.jpg http://i452.photobucket.com/albums/q...psdd1916eb.jpg http://i452.photobucket.com/albums/q...psdbda94d2.jpg
|
| Audiokarma |
 |
|
|
Hybrid Mode
