A HI-FI tube power amplifier 02

The high-voltage delay control circuit is undertaken by a 555 integrated circuit, which is a typical delay circuit. It can directly drive
the relay, and its delay time is about 30s. The working status indication is completed by a complementary tube 2SA733 and 2SC945. When the power is turned
on and the delay time has not expired, the ③ pin of IC2 outputs low level, and the VT6 tube conducts On, the red light HL2 lights up. Once the delay time is up,
pin ③ changes to high level. The drive relay is connected to the high voltage, and VT5 is triggered at the same time. The green light HL1 is on, VT6 is off,
the red light is off, and the whole machine is in working condition. The 6
    filament power supply adopts AC. Each channel power tube uses a separate group, and the voltage of each channel is amplified. It shares another group with the inverting drive
, so a total of four groups are needed, each group has a center tap grounded.
    The power transformer, like the output transformer introduced earlier, also uses an R-type iron core. Considering that the screen current of the power tube can
reach more than 100 mA during dynamic conditions, the transformer leaves a large margin, and a 360W motherboard is used for power.