Electronic Repair

Update - 2024/2025... My customer who owns this Fairlight was lucky enough to find a non-working pen a year or two later. It wasn't easy to make it work! There are no schematics for the pen. First, the pen was terminated with a 4 pin mini-XLR, so the option was to find the right connector to work with the original 7 pin connector on the monitor, or open the monitor and change the connector to a compatible mini-XLR. I was able to find the right part number for the original.. and Eaton Viking TNP07-100 Posi-lok. Then I found out the pins are sold separately! The pins are supposed to be crimped with a special $600+ tool, but I was able to solder the wires instead.

The “Hit” part worked, but not the “Touch”. Hit is the “mouse pointer” crescent shaped cursor that’s on the screen, and Touch is the “mouse click”. I tried about everything I could to open the bottom part of the light pen, but it would not budge without breaking the threaded plastic. Doing some testing with my oscilloscope watching the signals, I found that Touch is activated by sending the Touch signal low. I also found a broken resistor at the top of the pen connected to the CA3096 transistor array. After replacing the resistor, I was able to ground the origin of the touch signal at the front of the pen to get the function to work.

Now the pen fully works, but in a different way. The spring tip of the pen does not activate the function. However, if you hold the main part of the pen with your hand, you can activate touch by tapping the lower part of the pen with your finger. I believe the wire that’s connected to the spring is broken.