Here at the PITBULL HALL OF FAME we buy most every Stern game that comes along. On almost all of them, the drop target boards fail in a short time and the failure is always the same thing. The opto-gage Stern uses (Generic part number H21A1) is NOT designed to be used in a HIGH VIBRATION application.
After changing a BUNCH of them in the last year or so, I began to notice that when I removed them from the board, ALL the legs were sheared off cleanly and evenly where the leg enters the actual component (LED on one side, and PHOTO TRANSISTOR on the other) all the up inside the plastic cage. ALL THEY ARE IS PRESS FIT!
Just for shits and giggles, I replaced one on an AC/DC with an older style Williams # 5490-10159 (Generic # TCST 1103) which we also have in stock at all times.
Works fine.
The TCST 1103 does not have the flange to mount and solder to the board, but like any work around, there are trade offs. Over the years I have had very few failures of the TCST 1103 on Williams boards. Mostly they get chopped off by a mis-aligned drop target fin bashing them, or the LED side goes dim after time and just needs to be replaced. I do not remember ANY failure, even on flipper boards where ALL the legs came apart from the component.
As always, use EXTREME caution when working around surface mount components when changing this part. The markings on the TCST 1103 are NOT the same as the H21A1, but you will notice that 2 of the solder pads on the board are common. These are the holes you will insert with the common legs of the TCST 1103 marked with the "+" symbol.
Also, de-burr all holes! Do not scale drawings!