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  #1  
Old 07-26-2017, 09:47 AM
CPQ5360 CPQ5360 is offline
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Radio Shack Portavision (color CRT) suddenly died, dark out-of-focus image

I have a circa 1998 Radio Shack Portavision 5" color CRT TV I bought mint in the box a couple of years ago. A few weeks ago I finally put it into use, running a couple of hours a day.

Today I go to use it, and it seemingly died for no reason overnight. It now has a dark and completely out-of-focus image, and there's a subtle hissing/whistling sound coming from inside it. This is on both TV and monitor modes.

Any ideas as to what could have suddenly went wrong? I suppose I'll crack it open later and have a peek inside. I did test the power supply, which is supposed to be 13.5V, and it read 19V. I'm hoping that's just because I tested it with no load. I'll test it under load later.
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Old 07-26-2017, 10:09 AM
tom.j.fla tom.j.fla is offline
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What is the catalog number? Thats' how you find data for Radio Shack electronics. With that we VK'ers might be able to offer help. All the best,Tom.J _ p.s.model number is like this:16-000.
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Old 07-26-2017, 11:15 AM
CPQ5360 CPQ5360 is offline
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Catalog number 16-125.
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Old 07-26-2017, 12:19 PM
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You'll find more info under Memorex 16-125. We apparently had one in for repair - it was a cracked board, so I can't offer up any direct suggestions.

Dark and out of focus could be just about anything in the sweep/flyback area. Common on some of the smaller sets was arcing around the base of the flyback, near the screen (G2) control and focus lead coming out of the flyback. Again, just a generality.
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Old 07-26-2017, 05:44 PM
zeno zeno is offline
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Dark & no focus point to the HV divider which is almost always
built into the FBT ( flyback) as the focus & screen controls.
Normally I would measure the G-2 pin of CRT BUT there is
a chance of too much voltage that can wreck your meter.
Check for cold solder joints under the FBT first. Usually a pin
set apart from the rest & flat. To track down the noise you can
use a stethoscope made of an old paper towel tube. Odds are
the noise is coming from the FBT.

73 Zeno
LFOD !
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Old 07-26-2017, 08:44 PM
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Hissing sounds like hv, dust, flyback cracked from age.
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  #7  
Old 07-29-2017, 04:31 PM
CPQ5360 CPQ5360 is offline
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I found out what's going on. I did look inside the TV - everything was factory clean, no bad solder joints or loose wires, etc.

When I powered the TV on, I saw the problem - something is arcing at the very back of the neck of the CRT, where it connects to a socket on the circuit board where the flyback runs to. It's a small purple arc, emanating from under a blob of epoxy covering part of the back of the neck of the CRT.

I attached a picture showing where I see the arcing. I can smell ozone when it's turned on. I would assume one of the leads exiting the tube is broken.

Something interesting; it turns out the CRT was actually made by Samsung. I would have expected some nameless Chinese company.

I have no knowledge or training with repairing CRT displays, so I'm comfortable with calling this unit pooched. Such a shame since it was mint in the box, and I only put a few hours on it. Thanks everyone for the help.
Attached Images
File Type: jpg DSC00982.jpg (66.0 KB, 41 views)

Last edited by CPQ5360; 07-29-2017 at 07:03 PM.
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Old 07-29-2017, 06:49 PM
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That blob may have turned conductive. Just a thought
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Old 07-29-2017, 07:34 PM
WISCOJIM WISCOJIM is offline
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Looks like someone added that goop to try to stop the arcing in the connector.

.
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Old 07-29-2017, 07:34 PM
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Quote:
Originally Posted by mstaton View Post
That blob may have turned conductive. Just a thought
+1 - the focus voltage loves to find a path to ground. That goop is there to keep the CRT socket on during shipping, Carefully remove it from the socket and neck, and see if the problem disappears.
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Old 07-29-2017, 07:39 PM
CPQ5360 CPQ5360 is offline
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Thanks - I'll give it a shot. Any special precautions I need to take? I'm not at all comfortable working on a CRT - it's one of the few things I refuse to touch as an electronics hobbyist. I don't own an HV-insulated screwdriver, and I also don't know how durable the neck of the tube is, should the screwdriver I use to pry off the goop slips and strikes the neck of the tube.
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Old 07-29-2017, 09:21 PM
CPQ5360 CPQ5360 is offline
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I was able to remove the black goop - TV acts exactly the same. Arc is in same place and same size/brightness. Worth a shot though - thanks.
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Old 07-29-2017, 10:35 PM
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Sounds like your CRT socket has arced, carbonizing some of the plastic. Can you get a photo of the phenomena in a darkened room? Sure would help...
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  #14  
Old 07-30-2017, 01:17 AM
CPQ5360 CPQ5360 is offline
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Here are two more photos, with and without flash. Externally linked so you get the full resolution to zoom in. You can see the corona in the photo with no flash.

http://i.imgur.com/6auxjBh.jpg

http://i.imgur.com/6p3OXVj.jpg
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  #15  
Old 07-30-2017, 09:46 PM
mrjukebox160 mrjukebox160 is offline
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Bad CRT. Broken pin in CRT seal.
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