User's Manual

Maintenance GMH Series VHF Radio
Page 5-4 BK RADIO
VCO Board
PA Flex Circuit
• PA Assembly (in the heatsink casting)
Filter Board
PA Board
Accessory Board
5.3.1 Unit Disassembly
1. Remove the four corner screws from the back of the heatsink casting.
2. Carefully pull the heatsink casting from the core assembly.
3. Disconnect the two flex cables and two coaxial cables from the PA board.
NOTE: The black-end coax is the RX input to the receiver. The white-end coax is the exciter
input to the PA.
4. Place both thumbs on the back of the core assembly and push it out of the extruded housing.
5.3.2 The Control Head Assembly
1. Remove the PA Assembly.
2. Remove the 6 flat head screws around the Control Head housing.
3. Carefully pull the Control Head from the core assembly.
4. Disconnect the two flex cables from the Option board.
5. Remove the 2 flat-head screws from the audio amplifier and 2 pan-head screws that hold the unit
together.
6. Remove the audio heat sink.
7. Remove the Option board.
5.3.2.1 Control Board
1. Pull off the two rotary knobs from the front of the radio and remove rubber resistance washer
behind volume knobs.
2. Using the spanner tool, remove the nuts holding the rotary switches in place.
NOTE: The spanner tool (076-01475-0000) has been modified for use with GMH radios. Older
spanner tools may not have sufficient depth.
NOTE: These 2 nuts do not have the same thread pitch and are not interchangeable. During
reassembly, replace each nut in its original location.
3. Carefully remove the Control board by prying it up.
NOTE: During reassembly, check that the microphone jack is seated properly in the housing
before tightening the nuts on the rotary switches.