SF2: new issues to tackle

I am waiting for my parts to arrive, so in the meantime, let's investigate other issues.

With the ground kind of wonky, the system made a big BooooOOOOOmmmm wow sound when you turned it on, and then had a loud hum.  At the bottom of the cab I disconnected the woofer and now it's much nicer to work on and turn off and on.

I got the driver board in, I put it on to tournament mode free play, and got a few days of good gameplay and analysis before I noticed something new:  

The right slingshot solenoid was always engaged.  Well, actually not always, but always engaged when the flippers were active.

The Q relay (upper right in schematic) is in the cabinet and controls the activity on the playfield.

It is normally off, and when engaged it allows the pop bumper, slingshots, and main flippers to be active.

When the Q relay is not engaged, the solenoid for the slingshot ("Right kicking rubber") is no longer on.

The connector in the upper left, above, is labeled A3J5 and comes in from the lightbox, the driver board.
Solenoid 2 is controller via Q3, R64, C14, and D3.

The first thing I was curious about was if the switches on the playfield were jammed on or had wiring issues.  I used my DMM and confirmed full resistance across the nodes, and zero resistance when I pressed the switch, so they were operating nominally.
Here they are represented in the switch matrix:

click to embiggen

The adjoining switches in the matrix also all work, so it's not a switch problem.
I wonder if there could be a spontaneous failure of a transistor on the driver board?
In the meantime I can remove Fuse 17 and just play without the slingshot kicker.

yeah I should go learn how to measure across these properly.

Another piece of the puzzle: 
When I go in to test mode, I get the main test mode screen saying "TEST MODE:  USE L FLIPPER TO CHANGE / R FLIPPER SELECT" but then NOTHING happens.  Left, right flippers, and start button, all do nothing there.  WEIRD.
I noticed this issue at the same time since the first step to look in to the solenoid issue was to check the solenoid and switch tests.


EDIT:  removed fuse 17, disabling the right kicker, and now the test mode works again.
Also:  the switches on the slingshot are fine, the lights still turn on when hit.  This does lead me back to the  driver board components, as the switches are shared for the lights and the solenoid, and those are fine, and at the back end of the circuit the Q is doing it's job fine, so it has to be somewhere after the switch matrix and before the solenoid.