Difficulty

Difficult

Steps

3

Time Required

                          2 hours

Sections

1

  • Resistors
  • 3 steps

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  • BackCanton Subwoofer AS60SC

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Introduction

Cause: defective resistor

such SMD resistors usually last forever;

4 of my loudspeakers have already become defective.

This sealant is to blame, it is chemically aggressive and ruins the resistors.

Annoying when the beautiful subwoofer becomes electronic waste because of such a penny article .

What you need

Step 1

              Bad sealant
  • Unscrew 10 screws
  • Carefully remove the back panel, it sticks a little
  • Unsolder the speaker wire
  • Remove the ‘bad’ sealant as far as possible on the circuit board, It is not needed where there are no air holes to be sealed.

Unscrew 10 screws

Carefully remove the back panel, it sticks a little

Unsolder the speaker wire

Remove the ‘bad’ sealant as far as possible on the circuit board, It is not needed where there are no air holes to be sealed.

1024

Step 2

              Resistors
  • Expose the defective resistors and replace (desoldering is best done with 2 soldering irons)
  • R9 is well hidden, as is R14
  • R8 is hard to get at with a soldering iron, so I found another place to replace it, see Figure 3
  • Depending on how the sealant was applied here, other resistors may also be affected.

Expose the defective resistors and replace (desoldering is best done with 2 soldering irons)

R9 is well hidden, as is R14

R8 is hard to get at with a soldering iron, so I found another place to replace it, see Figure 3

Depending on how the sealant was applied here, other resistors may also be affected.

Step 3

              Circuit Diagram
  • Here is an excerpt from the circuit, with the MC33079
  • The 4th OpAmp (pin 12, 13, 14) is the low pass for ‘Crossover’
  • MC33079 is supplied with +/- 12 V
  • 0 V can be measured at all 4 OpAmp outputs, against ground, with the amplifier switched on. If not then something is wrong.
  • NE5532 is only used to control the LED
  • The power amp is a TDA7296 that runs fine

Here is an excerpt from the circuit, with the MC33079

The 4th OpAmp (pin 12, 13, 14) is the low pass for ‘Crossover’

MC33079 is supplied with +/- 12 V

0 V can be measured at all 4 OpAmp outputs, against ground, with the amplifier switched on. If not then something is wrong.

NE5532 is only used to control the LED

The power amp is a TDA7296 that runs fine

Follow the directions in reverse order to assemble your device

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                    Gottfried Silberhorn

Member since: 02/01/2022

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