Can anyone tell me if valve 5AS4 should light up when the set is powered on

I have picture failure on my set and wondering if it could be failed valve

Check the valve filement with your multimeter. Pins 2 and 8.

If you have a picture failure I assume sound is OK?
If that’s the case 5AS4 is working as designed.
Otherwise, measure high tension voltage on 5AS4.
Filaments should be alight.
JJ

5AS4 is like a big 5Y3GT, so yes the filaments will glow red across the top and also if you look down into the anodes. They tend to go gassy rather than open-circuit, but if yours isn't lighting up try another one. If you haven't got a replacement, luckily there's literally dozens of pin-compatible types.

Testing procedure:
1. Turn off set, unplug 5AS4
2. Use multimeter to check for continuity of the filament. If this fails, discard.
3. Use multimeter to make sure each anode is NOT touching the filament. If this fails, discard.
4. Use multimeter to make sure the 2 anodes are NOT touching each other (unlikely, but still...). If this fails, discard.
5. Visually check the filament. It should be white - not grey. You might find bits of it at the bottom of the valve. Or you might have low emission.
6. IF you have a working radio that uses a 5Y3G or GT, put the 5AS4 in its place, see if it works. Just don't run it for a while because the filament takes an extra amp (5 watts) of power.
7. If the tube has purple or blue lights, it's gassy. Discard.

If all this passes, you know the 5AS4 is ok. The next thing would be to check the filament voltage in the TV.