Replacing the -49 VARO pair with one bridge

Steps

• Take out the two screws holding the small 8 A bridges to their base plate.
• From the back, remove the four nuts holding the VAROs, desolder their leads and discard them.
• Mark the old VARO pads on the fuse side with a marker.
• Sleeve the upper AC lead of a 35 A 200 V wire-lead bridge with a 1/2" piece of 1/8" heat shrink; lay the bridge on the fuse side, minding the offset "+" lead.
• On the solder side, run a wire from the sleeved AC lead to the far AC pad; solder the other AC lead and the + and - leads.
• Bolt a heat sink to the bridge; this is required.
• Bend the leads to fit and solder the bridge in.
• Bench test before refitting (line cord on J2 pins 6 and 7); a clip-on breaker in place of F1 saves fuses.

Line voltage (120 V AC) is present on the rectifier board and its J2 connector; unplug the game before touching it.

Systems

• Bally MPU AS-2518-17
• Bally MPU AS-2518-35
• Stern MPU-100
• Stern MPU-200

Games

• Future Spa
• Space Invaders

Related tips

• How the -49 rectifier board differs from the -18
• The three Bally rectifier boards
• Replacement power supply board won't run the game: J2 ground pin not linked
• Game totally dead after running a vacuum from the service outlet: power cord
• Fuses blow with a brand new rectifier board: cold joint on BR1
• Getting at the bridges on -18/-49 boards
• The stock bridges are undersized
• Use 35 A wire-lead bridge rectifiers as spares

Source: Repairing Bally Electronic Pinball Games from 1977 to 1985, Part One, Clay Harrell (pinrepair.com)