I tried to power the PI1541 through the USB port first.It was getting stuck at the "searching for" screen.
I checked the voltages on the USB pads and the GPIO pins and found out there is a 0.7V voltage drop between them.That shows the USB power protection and regulator circuit is using quite a bit of power.
So I connected the power from the tape port direct to the GPIO pins.
It is possible to reduce the power consumption of Raspberry PI by disabling the HDMI,WIFI,Bluetooth,Ethernet and USB ports.I added the commands to config.txt file on the SD card.
dtoverlay=pi3-disable-wifi
dtoverlay=pi3-disable-bt
tvservice -o
dtparam=act_led_trigger=none
dtparam=act_led_activelow=on
tee /sys/devices/platform/soc/3f980000.usb/buspower >/dev/null
kernel_address=0x1f00000
force_turbo=1
I tried hooking it up to my LCD TV with the HDMI cable and found out it was still working.So these commands didn't do a thing.I will try to contact Steve White and ask him about this.