When using the Russian PIO K40-Y capacitors that Bob and I offer as an option, make sure they are insulated from the rest of the circuit,
from the circuit board, and any surrounding parts, such as the front octal sockets where you check bias.
I supply them with electrical tape on the bottom side, and heat shrink for the leads. Bob supplies heat shrink for the leads, but I'm not
sure if anything else. I now also stock heat shrink tubing (3/4" size) to completely enclose them.
The body of the capacitor is metal. If it touches anything else, something will short. Leave the leads long enough to space them away from
the PCB and away from the front octal sockets.
The first photo below shows stick-on tie-wraps to hold them away from the board and in place.
I couldn't' find any photos I had where it was obvious I had electrical tape on the bottom side,
the 2nd photo (it's the octal version) below shows where I fixed an amp that had a cap shorted to both the PCB and the front socket.
The leads were too short to space it up more, but I managed to squeeze some (white) electrical tape under it and in front of the octal socket.