This was a Kitchenaid KCM1204 filter-coffee machine, I bought it off Ebay cheap because its display had dimmed to the point of being unusable.
Turned out that the low-voltage power supply was supplying too little current, because the "dropper" capacitor (connected directly to mains live) had degraded. This is a known problem - e.g. from this post on EEVblog :
"Class-X capacitors are deliberately made with thin metallization so that they will self-heal easily. This limits their series current capability and causes them to lose capacitance over time. This is a common failure mode in capacitor dropper PSU applications."
The capacitor from mine is marked as 0.82uF, but now measures only 0.36uF. Time to replace it...
To repair:
1. *** UNPLUG THE MACHINE FROM MAINS BEFORE STARTING WORK! ***
2. Take the bottom panel off the machine (6 Philips screws).
3. Trace the mains cable, it goes into a small plastic enclosure - undo 2 screws holding the enclosure into the machine, pop the two halves of the enclosure apart.
4. Identify the dropper capacitor - large rectangular component, marked "X2", "280VAC", "0.82uF" in the case of this machine.
5. Purchase a replacement part of the same voltage-rating, capacitance and pin-spacing - ~£3 / $5 for one-off.
6. Desolder the original capacitor and solder in the replacement. Reassemble and refit the power-supply enclosure, then refit the bottom panel of the machine.
7. Plug the machine in - the display should now be readable again.
Turned out that the low-voltage power supply was supplying too little current, because the "dropper" capacitor (connected directly to mains live) had degraded. This is a known problem - e.g. from this post on EEVblog :
"Class-X capacitors are deliberately made with thin metallization so that they will self-heal easily. This limits their series current capability and causes them to lose capacitance over time. This is a common failure mode in capacitor dropper PSU applications."
The capacitor from mine is marked as 0.82uF, but now measures only 0.36uF. Time to replace it...
To repair:
1. *** UNPLUG THE MACHINE FROM MAINS BEFORE STARTING WORK! ***
2. Take the bottom panel off the machine (6 Philips screws).
3. Trace the mains cable, it goes into a small plastic enclosure - undo 2 screws holding the enclosure into the machine, pop the two halves of the enclosure apart.
4. Identify the dropper capacitor - large rectangular component, marked "X2", "280VAC", "0.82uF" in the case of this machine.
5. Purchase a replacement part of the same voltage-rating, capacitance and pin-spacing - ~£3 / $5 for one-off.
6. Desolder the original capacitor and solder in the replacement. Reassemble and refit the power-supply enclosure, then refit the bottom panel of the machine.
7. Plug the machine in - the display should now be readable again.