Wow, that Volcan is a beautiful example of a great Gottlieb game!
I repaired one along time ago. The only "mod" I did to the game,
is that I separated the pop bumpers and put them on their own
relay. It helped tremendously the dreaded ball jam/dead between
the point where the ball hits one pop bumper and bounces into the
other at the same time and does not recache back because the relay
is between moments of activation and resetting.

William's chime assemblies were constructed on the cheap.

Note: Bally EM playfields and SS playfields are slightly different.
------ The key is the pop bumper cutouts.
------ Once I had to do a playfield transfer of Bally's EK's EM pinball.
------ Everything was fine tell I got to the Thumper Bumpers...
------ had to use SS hardware to put the EM Thumper Bumpers together.

Bally's weakest link. The GI circuit needs to be redesigned...
Problem fixed on later models... [eg Bally Freedom ].
How to fix:
1) Add from transformer a second wire....WHT-GRN
1a) Add second wire from fuse block WHT-GRN
1b) Add Molex connector heavy duty. .093 to added wire.
2) Check fuses
2a) Repair fuse holders. if need be.
3) If Backbox has an open pin to one of the connectors, use it to add extra
--- lamp GI busing BRN wire.
4) Main objective is to remove current bottle necking from circuit.
EXAMPLE:
Extra brown GI wire inserted to backbox wire busing.
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Extra open pin, on connector, with extra brown GI wire inserted into the circuit.
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Extra brown wire fitted to female side of backbox connector.
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