4 x 6L6 with a single 5AR4 ? Well that's gonna be a problem, I find it hard to believe they did that. Most rectifier tubes are only suitable for use with one pair, i.e. 40-50 Watt amps. The only reliable way to rectify 100 Watt (four power-tube) amps is to use either solid state rectification or TWO tube rectifiers.