My original HP-25, ailing

[John Garza (3665)]

Also... ensure you have excellent conductivity with the battery. Even with corrosion removed, sometimes the metal plating flakes off. And Woodstocks only have one point of contact (the tangent of the circular disk contact) as opposed to two contacts against the v-shaped battery contacts in Classics.

On the capacitor - it is likely a filter cap, so you may want to check the power lines for noise on the scope.

-J