I've been working on this problem off and on for a while. Originally the ball on magnet switch stayed closed when the beam was interrupted. I bought enough parts to shotgun a fix since they were cheap and shipping was expensive. First, I replaced Q1. The switch worked correctly during test for about 10 seconds. Now it reads open all the time.

I replaced all major components in the following order: C-7 & C-10, L1, U-1, optos, U-3 with no change in status after each step. I did not replace U-2.

The switch circuit will show closed if I fire TV remote at the receiver board so that circuitry is ok.

I do not get any glow in a digital camera when pointed at the transmitter. It seems like I have blown out the IR transmitter. I have 10+VDC at J2-1 & 2. I do not know if this is correct or if I used the incorrect transmitter. The optos from the 10 opto board read ~1.5V but they have resistors in the 12 V line to them. The long range opto does not. I m down to my last opto bulb and am reluctant to replace the transmitter bulb until I figure this out.

Any help would be appreciated.Thanks.

BTW, I did find a source for the MC3373 opto receiver.

Chris, do you know if 10 VDC at the transmitter too high? Shouldn't it be ~1.7?

Bump. Can anyone confirm the voltages at the trasnmitter & receiver on the long range optos?

Thanks.

Just looking for someone to check the voltage at J2 on the opto 24 board in an operating game at this time.

Thanks.

Thanks. I'm getting 10+ VDC there. I was worried that voltage was too high for the optos, but apparently not. Guess I'll swap out known working optos from another spot on the playfield and see what happens.