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View Full Version : OT: Zenith System 3 Space Command Console TV



Liger Zero
05-22-2009, 09:00 PM
Just scored a "big" old console TV for free.

Its a 1984 vintage Zenith Space Command System 3. It's got a nice sharp clear picture (still) the wood-grain is intact, sound is perfect... one problem: The skin-tones are green. We're talking "Skanky Orion-Chick From Star Trek Green."

It's destined for video-game use so I can live with it, but I was wondering if any of you know "TV Guts." Back in the day Grandfather knew these things (in addition to "everything else") but he's dead.

Any chance it's something simple that a Home Shopper with a simpleton's understanding of electro-fu can repair?

Mad Scientist
05-22-2009, 09:31 PM
Any chance it's something simple that a Home Shopper with a simpleton's understanding of electro-fu can repair?

Ah probably not.
It sounds like this set needs to be “reconverged”. For this you need a thing called a dot generator and a lot of patience. This is a multi-step process tweaking and then retweaking a dozen or so controls.
It is not all that difficult to do but you would want to have a step by step manual to follow.

Evan
05-22-2009, 09:33 PM
Television circuitry can be truly bizzare. It's a challenge for the designers to find a way to save .000001 cents in some way. If at all possible a component will be designed to serve at least two jobs and if at all possible, more. Watch out for hot chassis systems too, even with transistor designs.

That model has a special skin tone circuit that broadens the red-orange output of the chroma demodulator. It sounds like it has gone haywire.

Liger Zero
05-22-2009, 09:37 PM
I see. Well it's for video-games so it doesn't have to be perfect. :)

Oh and "chroma demodulator" will be added to my technobabble file. :D

Doc Nickel
05-22-2009, 09:57 PM
The local junk-shoppe/permanent-flea-market store had, a few months back, a fair selection of TV repair hardware. Specialty test boxes for tubes, an ocilloscope looking thing with settings for "UHF" and "VHF", an another fancy box that had some obscure markings that I can't recall specifically but seemed to hint at tuning, focusing and collating a TV tube. (I'm assuming something to do with aligning the guns.)

I could have had the whole mess, at least five or six different testers, most with various adapter cables and the like, for maybe $50.

Doc.

clutch
05-23-2009, 03:09 AM
Some sets used to have red blue green pots that were exposed to the back that would let you make some adjustment.

Clutch

Evan
05-23-2009, 03:47 AM
That's because NTSC really stands for "Never Twice the Same Colour".

Being first doesn't always mean having the best system.

deltaenterprizes
05-23-2009, 09:20 AM
Sounds like the green gun in the picture tube is shorted. Look in the back for a "service" switch, switching it to the service position should disable the horizontal oscillator causing a single horizontal line across the screen. Removing the back of the set look for 3 potentiometers, one red, one green, one blue. There is a small aluminum clip on the electrical cord that causes the power to be removed when the back cover is removed, remove the clip and reinstall the power cord. CAUTION: there is 30,000 VOLTS going to the picture tube!!!!!!!! Using onle one hand and keeping the other in your rear pocket, turn the green pot down,that should be counterclockwise, then the other two, if the line remains green the green gun is shorted and the picture tube is no good, a very common problem with this type to set.
If the screen goes black when all pots are turned down slowly bring each gun up until a white line is achieved, turn the service switch to normal replace the back with power cord installed and your job is finished!
The best way is to bring up the red gun and one og the others until you get an orange line and then bring up the last one to get a white line.

Evan
05-23-2009, 10:08 AM
I do not think it wise for anybody to try servicing a CRT TV or monitor unless thay have had explicit training on how to service the product. A CRT with a defective bleeder can make you dead instantly. I refuse to work on them and I have training working on high voltage systems. I once took a 25,000 volt jolt from a colour TV many years ago and it is not an experience that I would recommend. In that event I was never closer than 4" to any part of the high voltage system. The insulated lead to the CRT had a crack in it and the charge followed a nearly invisible strand of dampish spider web to reach my hand (high humidity in the house). The charge traveled up my right arm, across my shoulders and up the side of my head to jump into the telephone I was speaking on.

It was about 30 seconds before I was able to speak as it was as if my brain had to reboot.

deltaenterprizes
05-23-2009, 11:50 AM
It is no different tha working on an internal combustion engine with spark ignition, that is why you use only one hand, the telephone was the path to ground in the other! If you had your hand in your back pocket you would not have gotten shocked.

mochinist
05-23-2009, 12:08 PM
good picture not required for gaming???? what kind of gaming are we talking about, my system is hooked up to the HDTV and looks better than most tv shows or movies with the right games

portlandRon
05-23-2009, 12:27 PM
Spent an earlier life repairing many Zeniths. Does not sound like a convergence problem. If convergence was off you would have red, blue or green outlines, like ghost, around images. Have you tried adjusting the HUE control which is on the front of the TV. If all the screen has a green tint to it the on the back of the chasie are level controls for the three color guns in the CRT. Try turning down the green colored one. Don't play with all the controls that are on a metal bracket screwed to the inside top of the cabinet, they are the convergence controls that control the deflection of each color gun and it takes special test equipment and hours of trainig/practice to get them set.

Evan
05-23-2009, 12:36 PM
It is no different tha working on an internal combustion engine with spark ignition

There is a very big difference between an ignition spark and the energy stored in a CRT. A CRT is a giant leyden jar which is a type of capacitor and can store a lot of electrons. This results in a lethal current to go along with the voltage. The high voltage from a spark coil or capacitive discharge circuit doesn't carry enough current for a long enough duration to be lethal. A good high energy ignition system will deliver a spark with an energy content of perhaps 200 millijoules. An average 26" CRT can store 6 to 10 joules of energy and bigger ones much more.

I didn't have my left hand near anything including the phone. I could have put it in my back pocket and it still would have happened.

Liger Zero
05-23-2009, 08:59 PM
I've got someone with more high-voltage-fu than I coming over to look at it.

Ultimate use is for video games, two video-game systems on the network, two separate TVs. :)