Narco At-50 And At-50A Installation - Trans-Cal SSD120-A-RS Series Owners & Installation Manual

Narco AT-50 and AT-50A Installation

Narco AT-50 and AT-50A Installations
The Narco AT-50 or AT-50A transponder will not accept data from the Trans-Cal
SSD120-(XX)A until the following modifications have been completed:
1. The strobe modification as outlined in Narco service bulletin no. AT-50A-5 dated 19 February
1975 has been performed on the transponder.
2. A modification to the Trans-Cal SSD120-(XX)A removing the data line decoupling capacitor
network.
The SSD120-(XX)A may be ordered from the factory with Mod. 1 completed, or the altitude digitizer
may be modified in the field as outlined below.
Instructions for field modification:
1. Remove the 4 screws, lockwashers and cover plate. Do not remove the D-Sub serial data connector.
2. Remove and discard the C1 capacitor network (refer to figure 1 below.) The network may be removed
using a pair of pliers to slowly rock the network back and forth until it breaks away.
3. Replace the cover plate, 4 lockwashers and screws.
4. A modification label is located on the side of the altitude digitizer. Using an indelible ink pen, place an
"X" in the box identifying modification 1 as complete.
Figure 1
15 Pin D-Subminiature Connector
C1 Capacitor Network
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