Garmin GNC 420 Maintenance Manual page 48

4.5.4 Remove Faulty Boards from the Main Chassis Top Cavity
Remove the Top Cover (see paragraph 4.5.1) to access the Main Chassis Top Sub-assemblies.
COM Board (Figure 7-2)
Steps 5 and 6 apply to 28V/10W units only.
28V/16W units have no posistor, no brass spacers, and use two
screws to hold down the PA transistor.
1. Remove the Com Board Covers (115-00203-00, 115-00205-00 and
115-00207-00).
2. Unsolder the wire from Coax Cable Connector (330-00070-04).
3. Remove two screws (211-63234-10) attaching the 25-pin connector to the Main
Chassis (125-00034-01).
4. Remove three screws (211-60234-06) securing the Com Board (012-00214-XX)
to the Main Chassis (125-00034-01).
5. Remove screw (211-60234-06) attaching the Posistor (925-D2120-00) to the Hex
Standoff (214-00023-00) on one side of the transistor.
6. Remove two Hex Standoffs (214-00023-00) on each side of the transistor using a
0.187-inch (3/16") hex socket tool and remove Com Board.
Inverter Board (Figure 7-2)
1. Disconnect the wire connector from the Inverter Board (012-00256-00).
2. Remove three Screws (211-60234-06) and remove the Inverter Board
(012-00256-00).
4.5.5 Remove Faulty Boards from the Main Chassis Underside Cavity
To access the bottom sub-assemblies, hinge open the Main Chassis from the Nav Chassis
(paragraph 4.5.3).
Map Board (Figure 7-2)
Remove the screw (211-60234-11) attaching the Map Board (012-00296-00) to
the Main Board (012-00347-3X) and lift the Map Board off the Connector.
400 SERIES MAINTENANCE MANUAL
P/N 190-00140-05
14/28V and
Page 4-5
Rev. C