No car subwoofer is complete without an amplifier. Very often, it works at limiting conditions and fails due to poor-quality assembly or components that do not have design parameters.
Necessary
Ohmmeter, screwdrivers, soldering iron, solder, laboratory power supply, thermometer, heat-conducting paste
Instructions
Step 1
Before starting repairs to the amplifier, remove it from the vehicle. First remove the main fuse for the power supply cable. Disconnect all power, speaker and signal wires. If these wires are the same color and the same diameter, be sure to mark plus and minus.
Step 2
Use a damp cloth to wipe dust off the amplifier housing.
Step 3
Disassemble the amplifier. To do this, remove the bottom cover, dismantle the mounting straps of the output transistors and the power supply keys, unscrew all the mounting bolts that hold the board to the case. Using a flat screwdriver, carefully separate the output transistors from the rubber-fabric pads, then remove the board from the case.
Step 4
Use an ohmmeter to locate the faulty output transistors. To do this, they will have to be evaporated, because the supply rails in amplifiers are usually combined, and one punctured transistor will short-circuit the entire power circuit.
Step 5
Look closely at the tracks and other parts of the amplifier's output stage. A broken transistor could damage some other parts. Using an ohmmeter, check the transistors of the pre-final stage and the resistors connecting them, as well as the tracks on the printed circuit board.
Step 6
While the output transistors are not soldered into place, do a test turn on using a 12V laboratory power supply to make sure that the voltage converter built into the amplifier is working. If the green LED is on, the voltage converter is OK.
Step 7
Replace any defective parts with the same or similar.
Step 8
Inspect the places of the rations of the replaced parts. Soldering must be of high quality.
Step 9
Using a thermometer, measure the temperature of the cases of the output transistors and write down the values on paper.
Step 10
Try turning on the amplifier. The green LED should light up. When turning on, be careful not to grasp the transistor cases with your hands, because a total constant voltage of 50 volts or more operates between their bodies. Turn on the amplifier for 30 seconds, then turn it off and measure the temperature of the cases of the output transistors. If the temperature of the transistor cases is no more than 2 degrees higher than it was, then you can safely assemble the amplifier.
Step 11
Disconnect all wires from the amplifier, grease all heatsinks of the output transistors and power supply keys with heat-conducting paste, put rubber-fabric gaskets on them that were under them, or replace them with mica gaskets.
Step 12
Screw back all the fastening bolts that hold the board, and then install the fastening strips of the output transistors and the power supply keys in turn. After each installed strip, check that there is no electrical contact between the transistor case and the amplifier case. Then replace the bottom cover.
Step 13
Install the amplifier back on the machine, making sure it is connected correctly.
