1: Schematic of DPDT switch and #1156 lamp wiring.
In one position, the power goes directly from the DCC
booster to the layout power bus lines. In the other po-
sition, the lamps are connected in series with each
bus line to limit the short circuit current to a safe value
while the trouble is tracked down.
1
Possum Hollow Railroad just as we were ready to run trains.
After an hour of troubleshooting with flashlights, screwdrivers,
and test lamps, we finally located one branch of the DCC power
bus that, when disconnected, would allow the entire main line
to operate once again.
After this disheartening situation, I began to wonder if there
was some easy way to trace the current flowing in a short circuit
without breaking any wires to insert an ammeter. I wondered
if a clamp-on ammeter would measure or indicate the current
flowing through a DCC track circuit. I knew that these meters are
designed to measure normal 60Hz. sine wave household cur-
rent, not the high-frequency square-wave used by DCC. Low-cost
clamp-on ammeters have become available from outlets such as
eBay and Harbor Freight for as little as $10. With such a low ini-
tial investment, I thought it was worth a try.
