10 year old HLR4667W, successfully replaced the bulb 2 years ago. The screen has started going to black randomly. Sometimes it takes 25 minutes, sometimes every couple of minutes. It does this with all sources, internal and external. The sound stays on. Turning the set off and then back on makes the picture come back - although the intervals between black screens are shorter once it happens the first time. The bulb appears fine & is glowing in back even when screen blacked out. All I've done at this point is made sure all external connections are ok and have unplugged it several times. Any ideas? I'm good at DIY but just need to know what to do or where to look. This forum seems like a good start.