The older Mettler AE series laboratory balances don’t have a standard power button, the main circuit is always running. As such the capacitors in the these balances which were manufactured in the early 80s are slowly in the territory of needing replacement. As such I decided to recap mine.
As a precaution since the circuit board contains lots of FET and a proprietary IC I took full ESD measures and did this with proper ESD tools, on an ESD mat with a ESD wristband.
Replacing the Y2 filtering capacitors
Right on the inlet socket are two WIMA 3n3 230V AC rated Y-class capacitors between N and P each to PE. I replaced these with
TDK B81123C1222M capacitors.
Storage capacitors
I then replaced the axial main capacitor (Philips 4700µF/25V) with a Vishay one. The two 470µF/100V and one 220µF/63V capacitors from Samsung I replaced with ones from Frolyt (ERY series). The small capacitor (whose value I forgot and can’t make out on my photos) I replaced with one from Panasonic.
I also as I always do write down the date on which I replaced the capacitors for reference:
The old capacitors were able to wiggle around quite a bit, so I applied a little of hot glue to ensure that the new ones don’t do that. This is especially considering that the circuit board contains a transformer that will induce 50Hz vibrations.
Finalizing
I then reassembled everything back together and it worked fine.
