ORIGINAL: Zaney1
In the old days, who can remember
, 4 dry cells were used in the reciever - this gave a total of 6 volts to receiver and servos. 5 x 1.2 volt= 6 volts so there should be no problem as long as its nicad or NiMh(1.2 volt per cell).
Your only mistake here is in assuming that each cell is only 1.2 volts. The cells may be rated as "nominally" 1.2v, but they can nevertheless give out significantly more than 1.2 volts. Have you ever looked at the voltage display on a transmitter that shows actual voltage (rather than just some color coding) ? My 10X shows 11.4 volts when freshly charged ... yet it has only 8 cells in it, so is nominally 9.6 volts. Same with your RX packs. Just try measuring the voltage sometime...
Gordon