Quote:
Originally Posted by StarquestMan
Just now getting back to this neat little TV after being busy for a while with other work. I checked out the heater voltage for the CRT, it is sitting at 6.19 volts. I used the TV for a little while just to check it out. After I turned it off I noticed a small splotch of colors on the screen that was sort of rectangular shaped and had a shimmering effect like a candle burning or a flag waving in the wind. I was very curios to what the HV was running at so I bought an old HV probe on ebay and when I got it I checked it for accuracy on another working TV that I knew the specification and it read right on. So I checked the Mitsubishi and it checked spot on 22.5 Kv as per the service manual. what would cause this strange effect on the screen after the set is powered off and is this harmful? I still need to correct the width deficiency but I'm guessing this isn't related although I have never seen this before on a TV so I don't know what to think.
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That's probably normal. It takes a few seconds for HV to bleed down on most sets and the same way it takes the CRT heater ~11 sec to warm up to full emission from cold it takes about as long to stop emission when turned off from warmed up. Capacitors in the sweep and gun drive circuits don't fully discharge immediately either so the set will still be semi-running off of stored charge and stored cathode heat for a few seconds after power off.
Each different circuit design will behave differently on switch off. Old monochrome sets would often have a lingering white dot in the center of the screen for the same reasons.
09-02-2020, 09:51 AM
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