28 Description TM9100 Service Manual© Tait Electronics Limited August 2005The main board 1^ is attached to the heat-transfer block H with threeM3x10 Torx-head screws B and the fastening elements J, 1# and 1$ of theauxiliary and RF connectors.The inner foam D-range seal G seals the auxiliary connector against theheat-transfer block. The power connector seal 1) seals the power connectoragainst the heat-transfer block.The power connector seal 1) of the 50W/40W radio (blue) is different tothe seal of the 25W radio (black).Main Board The main board 1^ is a printed circuit board in SMT design withcomponents on the top and bottom sides. A digital board D is reflow-soldered to the main board. Most components are shielded by metal cans.There are different main boards for each frequency band and each RFoutput power configuration.The internal options connector E for connecting an internal options boardand the factory connector (not illustrated) for factory use are soldered to thetop side of the main board. The control-head connector 1& (facing the frontof the radio) and the auxiliary F, power 1! and RF 1% connectors (facingthe rear of the radio) are located on the bottom side of the main board.The 50W/40W radio has a black power connector 1! and the 25W radiohas a white power connector.For more information on the connectors, refer to “Connectors” onpage 34.For heat dissipation, one of the screw bosses inside the chassis is in contactwith the underside of the main board. A larger copper plate at the undersideof the main board connects to the body of the heat-transfer block.The 50W/40W radio has an additional gap pad between the heat-transferblock and the main board 1^ which connects to an additional copper plateat the bottom side of the main board.Heat-Transfer Block The aluminum heat-transfer block H dissipates heat from the main board tothe heat fins of the chassis. The heat-transfer block has a contact surface tothe larger copper plate at the underside of the main board 1^, and a contactsurface to the rear of the chassis. All contact surfaces are coated with thermalpaste.Two self-adhesive foam seals G and I around the aperture of the auxiliaryconnector on either side of the heat-transfer block and the power connectorseal 1) inside the aperture of the power connector are fitted to the heat-transfer block.
