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  #31  
Old 01-22-2017, 12:05 AM
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510 miles! I commend your dedication. What state was it in?
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  #32  
Old 01-22-2017, 01:18 AM
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Got a scope? Remote issues are easy to fix with a scope, diddle stick, and the remote.

Most remotes consist of a few stages (often 2-4) of wide is band amplification, that then feeds tuned filters and relay driver amps for each function. I usually put a scope on the point at which the wide band amp splits off into the filters. If I get signal when pushing buttons on the remote then the wide band amp works and the filters need to be tuned or the rely drivers have issues. If I don't get a signal I scope the ultrasonic mike input to the chassis and if I get signal there then I troubleshoot the wide band amp. Let me see if I have a schematic for something similar...Zenith SC RX's (and most ultrasonic chassis) were all very similar just add or delete a stage between models.
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  #33  
Old 01-22-2017, 06:13 AM
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That remote switch is an odd sight, looks like something has to be removed for it to move. Those things often cause trouble. Then again, mine sometimes wouldn't respond until the clicker was held right up to the mic.
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  #34  
Old 01-22-2017, 09:29 AM
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The big filter cap is failing. It's gets real warm, and the picture will start tearing. After about 5 minutes, big white bars start running up the screen. But until all that starts up, it's not half bad.
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Last edited by TUD1; 04-22-2018 at 03:02 PM.
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  #35  
Old 02-01-2017, 05:41 PM
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Greetings & congratulations on an excellent find! I don't think I've ever seen a Zenith CRT with a line etched into it from loss of vertical sweep. Someone must have cranked the G2 controls and left it like that for a while for that to happen. Certainly replace that filter cap if it's warm to the touch. I can almost guarantee that the reason the space command chassis is dead is because of a particular electrolytic capacitor in the power supply of the space command chassis itself that has failed. If I remember correctly, the Space Command 500 circuitry is mounted on a PC board within that metal sub-chassis and somewhere toward the middle of the board is the very small radial 'lytic with a value of about 10uf @ 3 volts which is the suspected culprit. I've had a number of these sets over the years and with every one of them, that cap was the reason the space command didn't work. The last time I had one apart to repair was 10 years ago, so thats why my memory is a little foggy. The other caps within the space command chassis are probably OK as I think they are a different brand that held up better. When that 10uf cap fails (due to high ESR) it's basically an open circuit and you lose collector voltage on all the transistors which is why everything ends up being dead. You shouldn't need to align anything after replacing it. It's a nice quick and easy repair.
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  #36  
Old 02-01-2017, 07:22 PM
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Good to hear from you Doug, and thanks for the input. I'll certainly look in to replacing that capacitor too.
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  #37  
Old 02-03-2017, 04:45 PM
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FWIW, your two pictures of the chassis can create a 3D picture.

Cross eye mode, make your left eye shift on the right portion of the image, and right eye on the left.
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File Type: jpg SC500-3D.jpg (103.8 KB, 96 views)
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  #38  
Old 02-04-2017, 02:52 PM
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Quote:
Originally Posted by wa2ise View Post
FWIW, your two pictures of the chassis can create a 3D picture.

Cross eye mode, make your left eye shift on the right portion of the image, and right eye on the left.
I can't cross my eyes, but good one Bob!
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  #39  
Old 02-04-2017, 03:06 PM
walterbeers walterbeers is offline
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Take it from someone who used to repair these models, they are great sets and produced good pictures. I owned one myself and watched it for years. Only problem I had was when I hooked a VCR to it, the top of the picture would flutter and bend on certain tapes. There was a modification that could be made to make the horizontal AFC more stable, I tried it, and it made it better but not perfect. I no longer know or remember what I had to do to the circuit to correct the problem. I believe it has a 6U10 as the horizontal osc and AFC. The tubes were always a problem and it was best if they were bad to replace all four of them at the same time.
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  #40  
Old 04-10-2017, 11:45 PM
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Went to watch this set today, and I was pretty dissapointed with the image I got. Very blurry and out of focus. Took the set to my atelier, tweaked HV to the 26KV that it calls for, adjusted G2's, and adjusted focus. The NTSC test image looked amazingly vivid and sharp, but the image from the Directv box sucks. Even after adjusting.
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Last edited by TUD1; 10-20-2017 at 11:05 AM.
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  #41  
Old 04-10-2017, 11:53 PM
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Quote:
Originally Posted by TUD1 View Post
Went to watch this set today, and I was pretty dissapointed with the image I got. Very blurry and out of focus. Took the set to my atelier, tweaked HV to the 26KV that it calls for, adjusted G2's, and adjusted focus. The NTSC test image looked amazingly vivid and sharp, but the image from the Directv box sucks. Even after adjusting.
Weird. I'd say the CRT looks good, could this be an issue in the tuner? It looks like there is a lot of noise in the picture.
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  #42  
Old 04-10-2017, 11:58 PM
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I plugged the coax from the main VCR straight into the VHF tuner, and I got an absoluty disgusting picture. Extremely distorted, the color is WAY out of whack, and the focus has taken a dump. I don't know what's happened to this TV. It's unwatchable like this.
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Last edited by TUD1; 10-20-2017 at 11:05 AM.
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  #43  
Old 04-11-2017, 12:16 AM
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Quote:
Originally Posted by TUD1 View Post
I plugged the coax from the main VCR straight into the VHF tuner, and I got an absoluty disgusting picture. Extremely distorted, the color is WAY out of whack, and the focus has taken a dump. I don't know what's happened to this TV. It's unwatchable like this.
What is the Cable box set for .....480I or 480P output? I had an issue with a friend's 21" B/W set with the "fuzzies" - changing the output of the Motorola cable box solved the problems.

What gave it away was the kid in the room - his Wii has identical settings, and he knew what the setting should've been....RF output, but different settings available...
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  #44  
Old 04-11-2017, 12:23 AM
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You know, 3 pages of this thread, and not one mention of the chassis number. IMPORTANT if the search function means anything to anyone, or if (like me) you want to pull the service data and symptom/cure chart.

USELESS without a chassis or model number. BTW, the search function can only search text - don't rely on pictures to tell the model and chassis info.

Off to easier threads....

http://www.videokarma.org/showpost.p...64&postcount=1

at the top of every subforum for a reason.
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  #45  
Old 04-11-2017, 07:06 AM
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Yup that picture sucks but it has what it needs.
Try the AGC delay control. Turn til it gets snowy
then go the other way til it JUST clears up. Turning down the
sharpness ( on rear) will also help. The symptoms add up. If the box is overloading the set putting it right into the 75 ohms at tuner will make it
worse. The box has another challenge for the set. Very high contrast
that just wasnt around then. Without a comb filter the small
the small lettering will be terrible. If the set were tired it
would actually look better.

BTW also check the RF cable & matching transformer, they are
often crap now.

73 Zeno
LFOD !
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