Field Maintenance; General; Test Equipment; General Checks - Hitachi ATT-20 Installation, Operation, Troubleshooting

4.

FIELD MAINTENANCE

4.1. General

The following procedures may be used to check the ATT-20 at its field installation.
These procedures should also reveal whether the fault is in the ATT-20 or a related unit
or circuit. If fault lies with the ATT-20, the ATT-20 should be replaced with a new unit.
When installing the new unit, please make certain to follow all installation procedures
outlined in Section 2. Replacement units may be obtained through the STS USA Sales
Office.

4.2. Test Equipment

• True RMS reading DMM (Fluke 8010A or equivalent).
• 5.0 ohm, 5 watt resistor 1%
• 1.0 ohm, 5 watt resistor 1%

4.3. General Checks

Proceed as follows to perform a general check of the ATT-20 unit before performing a
series mode or shunt mode check:
1. Inspect all leads for breaks and loose terminal connections.
2. Check power supply voltage at terminals 1 (+) and 2 (-). The voltage should be
12 VDC nominal (9.8 minimum to 15.8 VDC maximum). Ripple voltage should
not exceed 1.0 Vpp.
3. Check the fuse on the transmitter circuit board. If it is open, replace it with a 3.4
Amp fast-blow fuse. If the fuse is intact, disconnect the transmitter and receiver
track connections at the unit. To test for proper operation in the shunt mode, refer
to Section 4.4. To test for proper operation in the series mode, refer to Section
4.5.

4.4. Shunt Mode Checks

Proceed as follows to perform a shunt mode check:
1. Connect the ATT-20 as shown in Figure 4-1.
2. Turn the RELAY VOLTS potentiometer fully clockwise. If the relay energizes,
proceed to step 3. If the relay does not energize, check the relay connections for
proper polarity and open circuits. If the same relay connections are good, replace
the ATT-20 with one of a unit of the same operating frequency and repeat steps
1 and 2. If the relay still does not energize, replace it with another PN-150B, 400
ohm coil (STS USA Part No. N322500-701).
Copyright 2019 SM 6299 Rev. 3, March 2019
ATT-20 Audio Track Transceiver
4-1