What Was the Walther FP Firing Voltage?

Bob LeDoux · Post by **Bob LeDoux** » Sun Dec 04, 2011 4:46 pm

Has anyone here measured the actual voltage on the big firing capacitor for the Walther Free pistol?

I am perplexed. I am under the assumption that the Walther used a live fire voltage of about 90 volts on its big capacitor. I was surprised when the pistol I bought was running about 150 volts. The capacitor in the gun was rated for 160 volts so this was pushing it towards failure.

My own pistol makes me think Walther had to raise the voltage above design levels to get reliable ignition. If this was the case, this could result in burnout of the capacitor and the firing FET; resulting in early demise of the electronic boards.

Does anyone here have measured data?

jbshooter · Post by **jbshooter** » Tue Aug 28, 2012 1:59 pm

Can you just put a multimeter across the capacitor when it's fully charged to find out?
I'm looking seriously at your project and information so I can ressurect an old Walther FP. Still have to find out more about the programming of the chip.

Bob LeDoux · Post by **Bob LeDoux** » Tue Aug 28, 2012 4:12 pm

My pistol factory board charged up to 150 volts. The capacitor was rated for 160 volts.

I needed 160 volts for reliable ignition. Current generation photoflash capacitors are smaller than those put in the Walther so higher voltage caps will fit the same space.

At 160 volts there should be good ignition. If misfires occur consider the possibility that the firing pin is not returning to its seated position after firing. This could be due to a weak return spring, powder residue in the firing pin chamber, or perhaps poor firing pin-chamber fit.

jbshooter · Post by **jbshooter** » Tue Aug 28, 2012 5:24 pm

Thanks Bob, but going back to my first question, can i use a multimeter to check the charged voltage at the capacitor leads.

Bob LeDoux · Post by **Bob LeDoux** » Tue Aug 28, 2012 5:51 pm

A digital voltmeter can be used to measure the voltage across the capacitor leads. Take care not to get zapped by the voltage. Because of the high voltage its best to use leads that clip to the wire. Place the leads before turning on the circuit. If the voltage climb approaches the voltage rating of the cap, turn it off.

Set your adjustment below the desired level and slowly adjust until the desired level is reached. If you go above the desired level, turn the adjustment back. It may take several seconds for the voltage to follow you back down.

jbshooter · Post by **jbshooter** » Tue Aug 28, 2012 9:06 pm

So on my other good FP i should connect the multimeter on the cap's legs and turn the gun switch on. i should see the voltage climb and then peak out?

Bob LeDoux · Post by **Bob LeDoux** » Tue Aug 28, 2012 10:50 pm

Yes, but the loading lever must be closed for charging to take place.