Datron TW7000MS, Technical Manual

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TW7000MS 4-1
CHAPTER 4
TECHNICAL DESCRIPTION
This chapter contains detailed information on each of the TW7000 boards. It
should be read prior to servicing or adjusting the TW7000.
Remove a board by pulling it out of its card slot. To service it in the radio,
mount it on the appropriate extender card, and replace it in the slot for
servicing. The following kits are available to help service and make
adjustments to these boards.
• 7000EXT extender kit
• TW7000TK tool kit
4.1 Power Supply Board
The Power Supply board consists of the power supply and its heat sink. The
board is mounted to its heat sink and then mounted on the vertical chassis
bracket located immediately behind the main heat sink, facing the inside of
the rear panel. The Power Supply board is connected to the rear panel via the
DC power cable which plugs into the 3-pin connector J26.
In addition to containing the regulators to generate the various DC voltages
used throughout the radio, the power supply contains reverse polarity and
over/under-voltage protective circuits. It has decoder and line driver circuitry
that takes the serial harmonic filter band-switching data from the Processor
board and translates it into parallel data for use with external high-power RF
amplifiers. This information is sent via connector J25 directly to the
Accessory 3 connector on the rear panel.
The TW7000 has an on-demand cooling fan controlled by a thermal sensor
located on the RF Power Amplifier board heat sink. This sensor sends a signal
to the processor when the heat sink temperature exceeds a predetermined
level. The Processor board sends a signal on the serial data line to the BITE
decoder circuit which turns on the fan.
The following table provides the interconnections between the Power Supply
board and the rest of the TW7000.
Note: There are several other lines that pass through this board, going
between J21 (processor) and J25 (Accessory 3 on the rear panel). Table 5-1
lists only those lines that actually interface with the circuitry on the Power
Supply board.