On the other circuitboard on the trough, there is an associated phototransistor for each LED on the front-most circuit board. This part doesn't fail a often as the others, but it might fail occasionally so here's some info on replacing it.

In the above photo of the Radio Shack LED, on the right is a Radio Shack Phototransistor, PN 276-145a. This part costs $0.99 US. This phototransistor looks considerably different from the original WMS phototransistors. It actually looks like a clear LED, but don't be fooled. I tried this Radio Shack phototransistor in mine briefly (for testing) and it appears to work okay. The flat edge of the phototransistor needs to be mounted closest to the top edge of the circuit board. That is, the flat edge of the phototransistor goes in the hole furthest away from the hole that has the little notch drawn by it on the circuit board.

An alternative to the Radio Shack phototransistor, I also purchased some from Digikey for testing. The Digikey phototransistors physically look much nicer. They have a gold base and a clear plastic tip. The first phototransistor pictured below has three pins. The pin in the middle needs to be cut as it is not used. Need to cut the third pin a close to the base as possible. I'm including these Digikey replacements for those of you who need to order parts on-line, you can buy them from Digikey. I didn't purchase any infrared LEDs from Digikey, but they should have an assortment and I can help you choose an appropriate one.

There are a couple different wavelength sizes and angle of visibility ratings. These need to be lined up so the little notch at the base of them lines up with the notch drawn on the circuit board. After a test of all three phototransistors that I purchased from Digikey, ONLY THE LEFT-MOST PHOTOTRANSISTOR WORKS in the IJ board. Apparently the other 2 are too sensitive to ambient light because they always showed the switch as a square indicating that it was receiving light. Only the left-most part PN104-ND worked and that is the one you should order. When installing this phototransistor you will need to remove the center pin from the part before installing. I just wiggled it back and forth until it broke off at the base.

Here's your options for acquiring these parts:

Remember, Digikey has a minimum order amount that you must fill. You may find it easier to send me a few bucks and get the parts for you than order a bunch of extra unwanted parts from Digikey.

Here's a quick list of the parts that I've tested:

For playfield opto switches such as: left and right ramp entrances, MPF hole switches, idol head position sensors, idol head entrance switch, under playfield tunnel opto switches. For each of these switches there is an LED in the white plastic side and a phototransistor on the black plastic side. These opto switches should use the same LED and phototransistor parts as listed above for the ball trough boards. I have not tested the Radio Shack parts in these opto switches but they certainly should work. Email me if you are about to try to replace your bad opto parts with Radio Shack parts. I'll try to provide any assistance I can provide. Remember that these parts should be installed in a certain direction. We MAY find out that we have to replace BOTH the LED and the phototransistor with the Radio Shack replacements to get it to work since the Radio Shack parts are probably designed to work with each other (the frequency of the infrared light waves might be matched for both parts).

For opto switches such as the drop-target sensors, flipper button sensors and mini-playfield limit sensors. These opto switches work exactly as all of the opto switches described above (an infrared sender, and a phototransistor receiver). The only difference is that the LED and phototransistor are physically enclosed in a single plastic U-shaped package. It's when something passes between the U, the switch is active. For example, there is a small flap of plastic on the drop-targets that pass through the U, or the mini-playfield limit uses a metal finger to pass between the U.

If you determine that you have a bad U-shaped opto part, you can first obtain a spare opto from your own machine! Indiana Jones shipped with 2 opto switches on each flipper button switch (the part where you actually press the flipper buttons... on the inside of the cabinet is the optos).

You can use the bottom-most opto for a spare as it is unused in Indiana Jones. These optos must be installed in a certain direction. There is a small notch at the base of this part which should line up with a notch drawn on the circuit board.

A second source might be Radio Shack. I believe that I saw this part when I was at Radio Shack. If you decide to try their part, let me know and I'll go and buy one to verify that it should work, and most importantly I can let you know the proper orientation if the Radio Shack part doesn't have that notch in the bottom of it for alignment.