To add a little to the collective knowledge for Feinwerkbau spring pistols.

I decided to replace the electrolytic capacitor in the trigger circuit on my Feinwerkbau 90. As electrolytic capacitors age two things usually happen - ESR increases and capacity decreases. An increase in ESR would cause lower voltage across the capacitor and less ‘punch’ delivered to the solenoid, a drop in capacity would mean the solenoid is energised for a shorter time.

The rate at which electrolytic capacitors age is largely determined by operating temperature, the higher the temperature the faster the aging. I estimate the original electrolytic capacitor in the FWB90 would be good for at least 20 years and operational to at least 30 years. My FWB90 dates to around the late eighties.

The part Feinwerkbau fitted is a Roederstein 1000uf 16V axial electrolytic capacitor measuring approximately 26mm by 12mm and manufactured in West Germany. Roederstein were taken over by Vishay and the brand no longer exists.

The closest replacement is a Vishay MAL202190518E3 1000uf 16V 20% axial electrolytic capacitor measuring 25mm by 10mm. This part isn’t stocked by either RS or Farnell, I ordered from Mouser. Alternatively a Nichicon TVX1C102MCD. I’d recommend using only quality Japanese or European manufactured capacitors.

If you are competent with de-soldering and soldering replacing the capacitor is straightforward. The circuit board can be turned over without de-soldering any connecting wires. You do need to unscrew the part at the base of the grip which houses the battery test light.