Perhaps scan and post the schematic for more useful feedback. As for the center-taps.... few power transformers have a center-tapped rectifier winding. If you are using directly heated rectifiers like 5U4, 5R4, etc., then using the center-tap for B+ is a great idea. If you're using indirectly heated rectifier like 5V4, 5AR4 (aka GZ32 and GZ34 respectively), then you should not use the center-tap as these have the cathode attached directly to one of the filament ends.
You need to better understand how the circuit works.... you simply can't assume that center-taps go to a particular tie-point. In many designs, the filaments have been raised above ground potential for various reasons, such as moving them away from ground, which can reduce hum coupling and/or ensure that the cathode to filament voltage rating is not compromised for certain tubes based on normal operating voltages, i.e., phase inverters could easily have more than 100 volts on the cathode.
With the 2A3, you really need to examine how it is biased. If cathode bias is used (very common) then the center-tap (if there is one) would traditionally be tied to ground via the cathode bias resistor. However, in some designs the center-tap for the 2A3 (and other DHTs) is unused as they employ a hum-balance potentiometer which in turn has the cathode resistor (and possibly the cathode bypass capacitor) from the wiper to ground.
So, unless "we" can examine the schematic, there's no easy and/or clear answer to your question.
Regards, KM
