Series Mode Adjustment With Cable Compensating Pcb; Lightning Protection - Hitachi ATT-20 Installation, Operation, Troubleshooting

3. Remove the hardwire shunt from the rails. The adjustment procedure is
complete.

2.8.3. Series Mode Adjustment with Cable Compensating PCB

Proceed as follows to adjust the ATT-20 in a series mode, with cable compensating
PCB installation:
1. Place a zero ohm shunt across the track connections at the feed end.
2. Connect an AC voltmeter (Vrms) across terminals 5 and 6 on the ATT-20.
3. On the cable compensating PC board, adjust the slug in pot core inductor L1 until
the voltmeter indicates a maximum.
Depending on cable length, peaking of the signal might not
be possible. After adjustment of inductor, place a small
amount of RTV in the pot core adjuster area.
4. Remove the zero ohm shunt.
5. Connect a hardwire shunt across the rails 65 feet from the ATT-20 track
connections.
6. Adjust the ATT-20 transmitter output level through the access hole in the top
cover until the relay is just energized.
7. Remove the hardwire shunt from the rails. The adjustment procedure is
complete.

2.9. Lightning Protection

Block wiring diagrams showing the wiring of surge and ripple protection for the ATT-20
in both the shunt and series modes of operation appear in Figure 2-3 and Figure 2-4,
respectively.
Two lightning protection devices are to be used with the ATT-20. The track connections
will be made through a USSP-21 secondary surge protection and the battery power
supply line will be protected by a surge ripple filter that uses a USG-A lightning arrester
across the power bus terminals.
The USSP-21 surge protector is wired to permit line-to-line protection using a low
voltage arrester and line-to-ground protection using high voltage arresters. Internal
circuitry of the USSP-21 also includes series line inductors as well as back-to-back
Copyright 2019
Note
SM 6299 Rev. 3, March 2019
ATT-20 Audio Track Transceiver
2-7