Williams System 3–11, Data East & Sega Lamp Matrix Harness Tester — Rotary Switch Lamp Diagnostic Tool

A lamp that won't light on your playfield could be the bulb, the socket, the matrix wiring, or the driver board — and you can't tell which without pulling things apart or chasing continuity with a meter. This Lamp Matrix Harness Tester plugs directly into the playfield's lamp matrix harness and lets you power any single row/column position on demand: dial in a Row and a Column with the two 8-position rotary switches, and that one lamp lights up if the matrix wiring and socket are good — independent of the driver board entirely.

Like the rest of our harness-tester line (Switch Matrix and Coil/Flasher), it works just as well on a playfield that's off the cabinet — on a restoration rotisserie, say — as it does fully installed.

Accepts a wide 9–25V DC input (9V battery, 12V adapter, or anything in between), so you can power it however's convenient on the bench or in the cabinet.

How to use it:

1. Connect to the lamp matrix harness headers: J7 (columns) and J6 (rows) on Williams, CN7 and CN6 on Data East. Note the pins are labeled as the connector actually numbers them — Rows 1, 2, 3, 5, 6, 7, 8, 9 and Columns 7-1 through 7-4, 7-6 through 7-9 — so a missing "Row 4" or "7-5" on the silkscreen is correct, not an error.
2. Power the board via a 9V battery or a 12V adapter.
3. Set the Row and Column rotary switches to the position you want to test.
4. The corresponding lamp should light; if it doesn't, the fault is in that lamp, its socket, or the harness between the tester and the lamp — not the driver board.

Compatible with: Williams System 3, 4, 6, 7, 9, and 11 (11A, 11B, 11C) — Williams never produced a System 5, 8, or 10; Data East; Sega.

Completes the harness-tester set alongside our Switch Matrix Harness Tester and Coil / Flasher Harness Tester.

Not to be confused with our older Lamp Matrix Test board, which simulates the lamp matrix to test the CPU/Driver board from the MPU side — this tester checks the playfield's lamp wiring and sockets directly, independent of the driver board.

See it in action: https://youtu.be/cNi8HlfSx7I