An elderly Pi2B v1.1 seems to have quit running. On power cycle both red and green status LEDs stay on, no flashes. Roughly one screen of boot output appears, then the screen goes blank and the monitor enters sleep mode. Re-seating the microSD card has no effect, unseating the microSD card has no effect, swapping the microSD card has no effect.
Plugging a usb cable into the usb ports and connecting a voltmeter to the red and black wires shows an initial 5 volts, then zero, then 5 volts after a few seconds. Putting the meter on the power supply leads shows 5 volts steady.
If I power cycle the Pi2 while the monitor remains powered and only a USB keyboard is connected the monitor shows the rainbow screen, about a page and a half of boot output, then blanks and enters "no signal" mode. The keyboard responds to caps lock.
Can anybody suggest other things to test?
Thanks for reading,
bob prohaska