kevin@ucbvax.BERKELEY.EDU (Wing) (02/25/86)
A friend of mine owns a Mitsubishi cs-1952R (or is it 1953R?) TV which is connected to the local cable system. Recently, a station on the cable system has gone "blank." No static, just blank. At least that's all I can tell. What really happens is that the TV, when trying to tune the channel, shuts down the video and audio. The power to the TV is still on, but if channels are changed, there is still no audio or video. Everything is restored to normal by turning the TV off for longer than 5 seconds and then turning it back on (on a different channel). My question is, what is in the signal at that channel that causes the TV to shutdown the audio and video? I can hear a relay or something in the TV switch the cause this, so I assume it is some kind of protection for the TV; which sounds like some unhealthy condition exists on this channel. I haven't been able to contact anyone with any knowledge at the cable company yet. Any info would be greatly appreciated. kevin@ucbvax.berkeley.edu
fish@ihu1g.UUCP (Bob Fishell) (02/28/86)
> A friend of mine owns a Mitsubishi cs-1952R (or is it 1953R?) > TV which is connected to the local cable system. Recently, > a station on the cable system has gone "blank." No static, > just blank. At least that's all I can tell. What really > happens is that the TV, when trying to tune the channel, shuts > down the video and audio. The power to the TV is still on, > but if channels are changed, there is still no audio or video. > Everything is restored to normal by turning the TV off for > longer than 5 seconds and then turning it back on (on a > different channel). My question is, what is in the signal > at that channel that causes the TV to shutdown the audio and > video? I can hear a relay or something in the TV switch > the cause this, so I assume it is some kind of protection > for the TV; which sounds like some unhealthy condition exists > on this channel. I haven't been able to contact anyone with > any knowledge at the cable company yet. > I cannot imagine anything being broadcast on cable or otherwise that would cause the problem you describe, unless there is a defect in the set. What is probably happenning is this: The power demand in a picture tube is greatest when the screen is in full black, _not_ when it's at its brightest. Now, some TV stations still transmit a carrier, with the blanking pulse, even when they're not broadcasting a picture. Our local PBS channel does this. So do most VCRs, and I suspect that the unused cable channel you're tuning into does the same thing. This causes your friend's set to try to hold full black level for extended periods. The click you're hearing is probably a circuit breaker that's shutting down part of the set's circuitry because the current demand is too high. In any case, the problem is in the set, not the cable. -- __ / \ \__/ Bob Fishell ihnp4!ihu1g!fish