One of the highlights of this year's Northern Lights Pinball 2012 event in Manchester was the debut of a Gottlieb Haunted House machine with some special modifications.
to read and learn more go to this link
http://www.pinballnews.com/learn/hauntedhouse/index.htmlYou need the following parts to do this multiball modification
Two ball-release solenoid and mechanisms
Wire guides
Schottky diodes BAT 42, 43 or 85
Two new switches
One-way gate for the upper playfield
One-way gate for the trough
Double-post for fitting above the trough
PI-80 board
Fabricate a metal guide bracket for the lower playfield
Mini-post for the extra ball lock (I chose to not fit one, but Pascal did)
Various lengths of cable and two fuse holders
Patience!