How to Disassemble a Small Guitar Amplifier

ID: 136492

Description: This guide takes you through the process of...

Removing the back panel will allow you to access the speaker and main amplifier chassis
Make sure that the amplifier is unplugged before starting disassembly
Identify and remove the screws holding on the back panel. On my particular Ibanez, 6 Philips head screws are used
Usually, guitar amplifiers will have a back panel that covers only around half of the amplifier cabinet, while bass amplifiers will have a back panel that seals the cabinet completely

The metal chassis houses the amplifier electronics themselves. You will need to remove it from the cabinet in order to access the power supply and main amplifier circuit board
Identify and remove the screws holding the chassis to the cabinet
Some mild adhesive may have been used as well. Once you are sure that all screws have been removed, gently push or pry the chassis away from the cabinet

Disconnect the speaker as shown, and remove the power lead clamp from the cabinet
The chassis should now be free from the cabinet
Be careful to avoid contact with the main board, as the power supply filter capacitors may still be holding a significant charge

To remove the amplifier board from the chassis, you will first need to remove the volume and tone control knobs
Use a flat blade screwdriver to gently pry the knobs off the potentiometer shafts
After removing the knobs, use a socket wrench with the appropriately sized hex bit to remove the potentiometer nuts
Make sure to keep the accompanying washers along with the nuts for reassembly

Remove the nut and washer holding the 6.25mm guitar input jack to the chassis
Disconnect any wires going from the board to other parts of the chassis, such as to the power switch or power transformer
Identify and remove any other screws that might prevent removal of the board. On my Ibanez, two screws held the power amplifier IC heat-sink to the chassis. Removal of the screws and their accompanying lock washers allowed the board to be lifted off with the heat-sink

Electrolytic capacitors can hold a dangerous charge for months or even years after a device has been powered off, thus, it is always a good safety practice to discharge the capacitors before working on an audio amplifier
Connect one end of an alligator lead to the chassis ground, and the other lead to an 10K ohm resistor
Identify the power supply capacitors and touch the 10K ohm resistor's open lead to each of it's leads for a few seconds
If you are paranoid, you may check with a voltmeter to ensure that the capacitors are safely discharged
It should now be safe to work on your amplifier's circuit board

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