The saga continues on the repair of the Jentec JTA0302B adapter that had once again failed a day after the 47uF capacitor was replaced. A diode next to the capacitor, also shrinkwrapped, seem to have charred the PCB. Removing it and testing indicated it was shorted and therefore toast. Since it was unmarked and the way it was connected across the 47uF capacitor suggested it is a shunting zener means I had to figure out what's what. The 47uF capacitor is connected to a chip. Scraping away the gunk that covered the chip shows that it is a UC3843B Current mode controller, ie the heart of a PWM based switching mode power supply. The capacitor is the power supply capacitor for the chip and the power supply is supposed to have a 36V zener shunt to protect it from start up over voltages. Since the zener goes 11V over the rating of the capacitor it may be part of the reason why the capacitor failed. So the 1/2 W zener was replaced with a 1W part which probably is the right idea since it seems the adapter is populated with underspec'ed parts. The adapter still acted funny as the voltage seems to ramp up real slow and had no regulation as the voltage dropped when a 100 ohm resistor was used as load. So no go. Careful examination of the rest of the components showed a bulging capacitor on the 5V output. OK thats probably bad. What about the rest of the capacitors. Good thing I have an EVB capacitor ESR meter and can check capacitors in circuit. Turns out all the original electrolytic capacitors, except one, had failed. If you ever see a Teapo capacitor, just replace it. Luckily I have some good quality Rubycon ZL series caps on hand with workable values and replaced the bad caps. I now measure a solid 5.16V on the output and feel quite good as I'm posting this through my DLINK router.
@ttclee it's supposed to be 47uf 50V. Underspec at you own risk.