# Lap Timer 2000 Question



## fargophil (May 15, 2011)

I have and have been using this program and setup for several years with no issues. Recently I had to disassemble my track as I was moving. In the process of moving I managed to mash one of the phototransistors. Does anybody who has this program and set up know what the replacement phototransistor would be? I have gdne some looking on Jameco Electronics site but of the 2 zillion available phototransistors it is impossible to determine which one I need.


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## Rich Dumas (Sep 3, 2008)

Go to the HO Slot Car Racing website, look under Electronics, then Lap Counter. That shows a Radio Shack part # 276-145 phototransistor. Radio Shack stores are now mostly all closed, but they still have an online business. https://www.radioshack.com/products/phototransistor


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## yellerstang (Feb 20, 2012)

Get the original Radio Shack part number, any decent electronics supplier should be able to cross it to a valid number.


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## Rich Dumas (Sep 3, 2008)

The phototransistor that you use must be matched to the emitters. Both the transistors and emitters operate over a very narrow frequency band, so even a slight mismatch would result in missed counts. 850 and 950nm seem to be the most common values for both the emitters and detectors. Radio Shack sold emitters and detectors in the same package as part number 276-142, but those do not match. 
Since you have the Lap Timer 2000 system that Greg Braun sold he would be the one to ask about the sensors if you wanted to be sure about what to order. The sensors are not listed as spare parts on the HO Slot Car Racing site. The sensors are not very expensive, probably shipping would cost more than the part. Someone out there in cyberland posted that Jameco Part no. 2129385 is a good replacement for the RS part. If you have not confirmed what the proper frequency should be you could order a few of each.


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