- Heaters: 150ma per tube (~2.5x that on startup)
That's incredibly conservative (and based on a 12.6V supply, they will pull less on a 9V supply). Heaters can get warmed up with less margin from operating current, it just takes a little longer.
- Plate current - 8-10x (HV/Rp+Rk)) per tube
Since these use an SMPS for the HV supply we're pulling everything from a 9V rail, so this doesn't give much information. The NE555 based supply is not terribly efficient, I believe I measured it around 75-80% a few years ago, but that depends on how many tubes are in there. This means that
Power out = Power in * 1.25,
So if we're pulling 4mA for plates with a 240V rail, that's 960mW, but we're losing about 240mW in efficiency losses, which basically means heat. So in this example we would be pulling a total of 1.2W from the 9V input rail, which means 133mA is being pulled.
It's also important to note that not all 9V power supplies are created equal. I've had some supplies that can pull as much as 125% of their rated current during tube warmup, and I've had others that won't even pull 100% of their rated current before shutting down. So my numbers above are not exact, but they're safe numbers for me to suggest.