Without having a Dirty Harry anymore, my guess is those optos are accessed by removing the parts above them rather than below them. The removal of the magnet is probably unnecessary. But have you already figured out you need to do this?

Switch edge test, stick something in there to block them. They activate? Use a bright incandescent flashlight, that activate them? These help determine if they work or if its the transmitter or receiver that's bad before tearing everything down.

That's the handiest diagnostic on your game. I can't imagine fixing switch problems or error dots without it. You go there and manually trigger any switch and see its results.

It should be flush. You can adjust the height by loosening the big nut and turning the core with a flat blade but if its already mushroomed, you should probably leave it alone.

I have a big bright incandescent light. I think flashing it in there at the angle you snapped the photo might even be enough.

Test the light on other working optos to verify your light works.

Bumping this up because I had the same error and recently got it fixed with some help. You do have to take off both main plastic ramps to get to this opto--it's not accessible from the underside. It'll help to take off the backboard panel (only takes like 8 screws and one connector to remove it). Once you get access to it, look at the wires where the opto connects. Mine was failing because one of the wires had disconnected from the opto. A little solder and we were back in business!

Not sure if this is the same game, but I recently bought a Dirty Harry from RTR.

The game is mint, but it did still seem to have this switch 42 issue.

Turns out (in a sense of closure) that a wire was broken off both the transmitter and the receiver (two broken wires). Once those were re-soldered, it worked like a champ.

Thanks again, RTR (Mike). I also changed out the mushroomed magnet core. Everything works great!

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