[ms660]

Is that using the lamp limiter?

The HT current you have measured is only part of the picture as it's not the total HT current that flows through all the amplifying valves, the largest contributor is normally the sound output valves anode current because it's operating in class A with a low value resistive part of the load (The output transformers primary resistance)

You need to measure that current and add it to the 13mA that you've already measured/computed.

Lawrence.