Hidden function

Test SW77

The secrets of the test mode

Planned functionality
but not documented by Gottlieb.


By analyzing the TEST mode code of the SYSTEM 80A, we identified a particular routine whose function seemed quite mysterious. Code

Indeed, it reads the state of the switches SW17 (left coin mechanism) and SW77. The latter is not totally unknown, because we had already discovered its hidden utility in the SYSTEM 80. But the service printer having been removed on the SYSTEM 80A, the SW77 had in principle no longer any assignment.

Why these two contacts?

In fact, GOTTLIEB added a function in the pinball test mode, but then failed to document it.

On a test bench, the SW77 is originally wired whereas it is not in a pinball machine. Also for the same functionality to be available on a test bench, or on a pinball machine, they have planned to be able to use the left coin mechanism contact (SW17) instead of SW77

The reason why both contacts can be used is practical. The left coin mechanism being easily accessible when the door is open, it was wise to use it, rather than rewiring and adding a push button for the SW77.


The added function is very easy to understand and only works with tests #16 (lamps) and #17 (solenoids and sounds).

These two tests normally cycle the lamps, or operate the coils and sounds sequentially. But sometimes, we would like to repeat the test for a single lamp, coil or sound.

This is precisely what the SW17 and SW77 are for!

Simply keep one of these contacts pressed for the test to stop progressing and regularly replay the current element. Thus, as long as the contact remains established:

  • The current lamp is flashing
  • The same coil is regularly activated
  • The same sound is repeated
Last update of this page: December 24th, 2022

French Tech


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