These pages will depict my attempts to fix the K1800FX. Wish me luck!
There was no hint of it going to die nor it was being abused.
Accessing to the PA electronics through the speaker hole:
The LPA1180 Rev. J amplifier:
A general view of my main workbench, with the amplifier on it;
This is the PCB, traces side:
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:
The PA with the drivers and power transistors removed. Both power transistors are shorted. Drivers measure fine on my PEAK DCA75:
These are some lousy looking solder joints, which I later resoldered:
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:
Now I am waiting for the transistor replacements to arrive.
Here I will add the repair work, once I get the spare parts...
K1800FX repair Part II
Go back to WORKBENCH INDEX