I have an odd issue on my TZ. I can trigger the Opto receiver of Switch 75 (Upper Play field Exit) with a flash light. I can point the transmitter of Opto receiver of Switch 75 (Upper Play field Exit) at the receiver of Switch 76 (Lower Play field Exit) and the light triggers the 76 switch. From this I know there are no issues with the Opto transmitter of Switch 75 (Upper Play field Exit).

I can not get the transmitter of Switch 75 (Upper Play field Exit) to trigger the receiver of Switch 75 (Upper Play field Exit). ... even if I hold them face to face. I have replaced the receiver twice.

The receiver for Opto receiver of Switch 75 (Upper Play field Exit) is much less sensitive than the receiver for Opto receiver of Switch 76 (Lower Play field Exit). If get the flashlight anywhere near the Opto receiver of Switch 76 (Lower Play field Exit), it switches. Receiver of Switch 75 (Upper Play field Exit) takes a direct beam from the flash light to trigger. I am determining if the switch switches by using the edge test.

I have reset all the connectors I could find. Any thoughts? Replace the Opto board? I am going to pull the mini play field now and look for a connector or short there.

Already replaced the 75 sender and the receiver. Receiver twice. Not sure why the 75 receiver is not sensitive.

Thanks for the tips. Heading out of town and it will be a couple of weeks before i’ll be able to work on it again.

What do you think about the replacement Opto boards?

Well, it doesn’t look like you can buy the Opto board.

Would one of you guys send me a link to the LM339 chip and socket? I’ll go ahead and order and swap it if needed when I get back in town.

Thanks. I have done cap kits before, but not a chip.

I was able to purchase an Opto board, but still have the same issue. Now I have a spare .

I only have 9.6 volts ot the black 75 receiver. I checked the connection plug at the mini play field and I have 12 there. I ohmed both wires and they have low resistance. I am guessing I have a short somewhere on the mini field.

I can not find a short. Anyone got any ideas? Un-solder one wire from the receiver and check with the circuit open?

Well figured out part of the problem. The receiver was hooked up backwards. Believe it was that way when I got the game. Now it reads 12 volts soldered in and is sensitive to a flash light.

Now it appears the transmitter is not working. It reads 12 volts hooked up. The others read 1.4 volts hooked up. I know it was working the last time I worked on the machine.

Would the receiver hooked up backwards cause any issues with the board or transmitter?

I have 12 volts from ground to the gray wire feeding the 75 transmitter. 0 V on the other side (black wire) to ground. I assume this means my Transmitter is bad as it is not conducting electricity. I'll reflow the solder connections to see if that helps. Else I guess I need to order a new transmitter. Thoughts anyone?

Swapped transmitters. Problem follows the transmitter. Ordering a new one.