- 1). Turn off the amplifier. If it is a tube amplifier, leave it to cool for 10 minutes. Moving an amp when the tubes are hot puts them at risk of shattering.
- 2). Unscrew the back panel of the amplifier. Typically, there are approximately eight screws, four on either side, anchoring the back panel to the amplifier cabinet.
- 3). Unscrew the lugs holding the amplifier chassis in place inside the cabinet. Slide the amplifier chassis toward you. The chassis is the steel box inside which the circuit board and transformers are located. If you're working a tube amp, the tubes are typically located on top of the chassis.
- 4). Unscrew the chassis lid to expose the circuit board.
- 5). Unscrew the circuit board from the base of the chassis. Once unscrewed, rest it on its edge so you can access the base without disconnecting the wires. Locate the transformer to be replaced. The transformer is the metal square located on the end of the circuit. Universal audio transformers are used as output transformers. The output transformer is located at the opposite end of the circuit board to the power supply.
- 6). Melt the solder joint fusing the output transformer connector pins to the base of the board. Use a a clean soldering iron to do this. Remove the soldering iron when solder flux rises from the connector pins. Leave the pins to cool for five minutes.
- 7). Wipe away any solder residue. Brace the transformer against the board with your weaker hand, straighten out the pins with your dominant hand.
- 8). Put the board flat and unscrew the top of the transformer. Slide your soldering iron inside and melt the solder joint fusing the wire to the primary winding. Pull the wire away from the winding and tape it to the board.
- 9). Lift the transformer away from the board.
- 10
Slot the replacement wire on the board so the connector pins protrude through to the base. - 11
Tip the board on its side and press the pins flat against the conductor strip. - 12
Solder the connector pins to the base of the board. - 13
Lay the board flat and screw it back in. - 14
Unscrew the top of the universal audio transformer. Remove the tape from the wire and feed it into the transformer. Solder the wire to the primary winding. Because the windings cover a wide range of impedance, there is no need to modify or replace any other part of the board, such as resistors or capacitors.
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