The dozer blade won't rise in a game, though it works in test and the eddy switches in front of the blade and Ted's head work.

Roadshow: bulldozer blade won't go up in play

Cause: One of the two U optos on the dozer opto board that report blade position is dirty or failing, giving an in-between level (around 0.4 V) instead of a clean 0 or 5 V, even if it looks fine in switch test.

Checks

• Measure the opto outputs for a clean 0 or 5 V.

Fix

• Clean the optos with a swab and glass cleaner; replace them if the fault remains.

Systems

• WPC DCS

Games

• Red & Ted's Road Show

Related tips

• Eddy sensors: electronic ball switches under the playfield
• Adjusting an STNG, Theatre of Magic or Roadshow eddy sensor
• Eddy board LED will not turn off at any pot setting

Source: Repairing Williams/Bally WPC Pinball Games from 1990 to 1999, Part Three, Clay Harrell (pinrepair.com)