EB5AGV's Workbench: BEHRINGER K1800FX Repair

The amplifier which let me down!

I am playing keys now (May 2023) for about a year on a band. On last gig (13th May 2023) my Behringer K1800FX decided to let me down in the middle of 6th song from a total of 17... It was not a great moment but, luckily, I had an smaller amp, a Behringer B205D monitor, which let me continue playing and end the gig.

These pages will depict my attempts to fix the K1800FX. Wish me luck!


K1800FX repair Part I

There was no hint of it going to die nor it was being abused. I got this 2009 unit used, just a couple months ago, but it was in very good shape and with low hours on it.

Behringer K1800FX

Behringer K1800FX

Accessing to the PA electronics through the speaker hole:

Behringer K1800FX

Behringer K1800FX

The LPA1180 Rev. J amplifier:

Behringer K1800FX

A general view of my main workbench, with the amplifier on it;

Behringer K1800FX

This is the PCB, traces side:

Behringer K1800FX

The only hint of what could have caused the problem is a tiny piece of metal, embedded on the thermal compound, found almost touching two pins of a power transistor:

Behringer K1800FX

The PA with the drivers and power transistors removed. Both power transistors are shorted. Drivers measure fine on my PEAK DCA75:

Behringer K1800FX

Behringer K1800FX

These are some lousy looking solder joints, which I later resoldered:

Behringer K1800FX

After some more checking, I have found that the current measuring resistor (used to set BIAS) was damaged, measuring about 1.5 Ohm instead of the nominal 0.1 Ohm, so I have replaced it with an Ohmite one:

Behringer K1800FX

Now I am waiting for the transistor replacements to arrive.


K1800FX repair Part II

Here I will add the repair work, once I get the spare parts...


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