In article . com, "Alec
S." wrote:

Matti Adolfsen wrote:

The one to the left is marked "8054 HN 3C31". The one to the right is
marked "S78L 05ACZ 326"

I don't know how to test if the 78L05 is good or not. If it is bad,
I'm guessing that an electronics or surplus store would have them
right?

Alec-

In your situation, substitution may be the best way to test the 78L05.
Otherwise you can search the web for a connection circuit. Then remove it
from the circuit, apply a voltage to the input through a current-limiting
resistor and measure the output. Be sure to note its orientation on the
PCB before removing it!

It should be easy to find. An electronics shop that carries the NTE
series of replacement semiconductors is likely to have one. Otherwise
search the web for places like Digikey and Mouser. The trick will be to
find a place that will sell you just one (or two for a spare), without a
huge minimum order charge.

Fred