We have a 1998 Toshiba tv. Its a 50" screen with

Hi,

This is an indication of out-of-regulation in the power supply section. This is cause by leaky/dried electrolytic capacitor in that section. It will dropped the supply from normal voltage and will disable the unit.It needs a little warm-up to make itself stable but the symptom will get worst until the unit will not even power up. Sometimes it has a bulged/dome at the top but not all, it is better that you have acapacitor checker/tester to determine its condition. Your unit will back to normal again if the leaky/dried capacitor is isolated. If you don't have a capacitor checker, replace all electrolytic capacitor in the power supply section, it will not cost you much because this is one of the cheapest part on that board. Watch this video for more info regarding electrolytic capacitor.

If you don't have necessary tools and test instruments, and can't do the job yourself, I would advice you to look for a professional to troubleshoot the problem. Don't attempt to work in the power supply if you don't know the safety precaution of handling it, there some stored electricity enough to hurt you with a little mistake only.

Hope I helped you.

Have a nice day!

Thanks for using Fixya.

Jdvillanueva