robb wrote:

Regarding the L387, since i had already removed it hat was asy
to test.

I am pretty sure it is bad from what you explained. that is 5V
regulators only output 5V .

when i applied a 5V/1A DC source to Vin/GND i measured 3.47V
between Vout/GND.
when i applied a 18 V / 3.5A DC source to the Vin/GND i measured
8.37V between Vout/GND

With a load or no load ? If there was no load on the regulator output then
that's quite possible even for a good L387. You must have a load resistor of
around 470 ohms on the 5V output for testing for the chip to regulate properly.


an LED load between Vout/GND caused the L387 to get very hot
quickly.

An LED with no series current limiting resistor might well do that ! You should
have a resistor of ~ 150 ohms in series with the LED.


so a new L387 is in order so that i can complete the other tests
that you TM and others have suggested

It may not be necessary. Your testing used flawed methods.

Graham