Feature lamps out on a -49 supply; TP1 low or dead while F1 is good, or F1 keeps blowing.

No TP1 voltage on the -49 board: failed VARO rectifiers

Cause: One or both VARO dual-diode rectifiers (the heat-sinked devices at E9 and E10) have failed.

Checks

• Measure AC between the metal cases of the two VAROs: about 9 to 10 V AC is normal.
• With AC present and TP1 low or missing, a VARO is bad.

Fix

• VAROs are no longer made (NTE6200, 6202, 6206, 6208 or 6210 sometimes substitute). Replace the pair with one 35 A 200 V wire-lead bridge.

Systems

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

Games

• Future Spa
• Space Invaders

Related tips

• One controlled lamp dead even after a new SCR: lamp driver board fault
• Auxiliary lamp boards drive special backbox lighting with MCR106 SCRs only
• How the -49 rectifier board differs from the -18
• One controlled lamp does not light
• A playfield target lamp never turns off
• On Baby Pac-Man and Granny, a GI fuse kills the feature lamps
• Fuses blow with a brand new rectifier board: cold joint on BR1
• Feature lamps dead after an MPU repair, GI fine: reseat MPU plug J3

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