Coffee Machine rescue

Repair Cafe meets coffee machine!

Our fully up-market (sic) pod coffee machine, that’s only a bare ten years old, suffered a seemingly terminal malfunction recently – failing to power up when commanded.

A few die-hard repair-cafe types brought their expertise to bear to troubleshoot the device – hopefully back to working condition.  Close scrutiny of the printed circuit board (PCB)

after some determined disassembly (not recommended for the faint-hearted) showed a burnt out resistor.

This, after some discussion as to the true value, was replaced but only after discovering the solder was a high-tin level solder that only melts at 450 degC!

               

 

Following partial re-assembly of the machine the power-on test showed that there were other components faulty and the resistor was just a sacrificial component as it burnt out immediately.

At this point the heavy reinforcements were needed for a deeper diagnosis. Another member weighed in with some informed circuit and component analysis.  This suggested that the offline switcher LNK304GN appeared to be faulty and indeed was found to have a low ohm resistance ~240 ohm across the Drain and Source pins (but also mindful that other parts of the circuit may be causing the low 240 ohm resistance).

Plus

The LNK394GN “appeared” to have generated some high heat to melt the part of the plastic casing of the IC.
 The reference schematic  shows the D(Drain) and S(Source) which PWM switches the power in to the secondary part of the circuit.
After some probing with the multimeter it was decided to reach out for some further assistance.  This came in the form of the online forum eevblog.com and confirmed the measured resistance did indicate a fault.
Next steps are to replace the LNK304GN and test and replace any other associated components around this IC.
More to follow as we seek to restore our revered coffee machine.
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