Fender Power Chorus Combo Amp Is Intermittent

The lights are on but no one is home regardless of what knob we twist.  Can the Unbrokenstring Crew sort this out?

 

More Made In U.S.A. goodness!

 

Why am I not surprised?

 

The chassis comes out the back of the cabinet.  Nothing is really amiss at first glance.

 

Touching these components causes the audio to work properly.  The problem lies somewhere in this vicinity!

 

All those pretty red Fender knobs come off.  Fortunately, they are all the identical.

 

And, all those nuts come off before the circuit board can be removed from the front panel.

 

These screws fasten standoffs that support the rear edge of the circuit board.

 

It appears, at first glance, that the heat from the power resistor melted the solder at this joint.  This is directly underneath the large rectangular power resistor seen in an earlier picture.

 

On closer inspection, we can see that the trace leading away from the component lead is cracked.  I speculate that the resistor expanded at a different rate than the circuit board and cracked the copper trace.  Once the copper was cracked, it became a ‘hot spot’ and accelerated the failure of this connection.

 

A piece of 24AWG copper bridges around the cracked trace.  It will take a long time for this to crack!

 

At least I have some automation to put all these fasteners back where they belong.

 

While the unit is apart, we can take an opportunity to clean up the rest of the unit.

 

This unit appears to be unchanged from the first picture, except now it plays.

Thanks for reading all the way to the end!

CONTACT – David Latchaw EE
281-636-8626

Please follow and like us:
error