Hi, I have an onkyo tape deck (ta-2058 for those interested) where there's this method for calculating the tape left. Basically it reads the speed of both reels with two LEDs and two phototransistors. The output of those photot. goes in two transistors, a double not logic gate (not sure why) and then finally in the control IC. In the attached schematic you can see this circuit on the right.
Unfortunately one of those sensors doesn't work. On the output of TR1 all I get are 5v (the supply) even if the tape is not turning.
On those transistors (sot23 package) I can only read L5 which doesn't tell me anything what to look for a replacement. Of course on the service manual there's no mention of that circuit
Can someone help figuring this out? Thanks!