As CarCode said these are NPN (BDW93B) and PNP (BDW94B) darlington power transistors in a T0220 plastic package. TR4 and TR8 would be another pair of 93B/94B.
The numbers 8923/17 are date codes, made in 1989 weeks 23 and 17.
Basically the transistors act as a switches to the autopilot
, one pair turns on to drive the motor
one way and the other pair for the opposite direction. If one of the transistors does not turn off when it should then it will cause a short with the results as you have seen. Good news is that you can replace the transistors, bad news is they may not be the root cause and will just burn up again. Hard to tell without digging further into the circuit.
Try DigiKey, Allied Electronics
, or Mouser for replacements
. I'm sure there are substitutes if you can't get the BDW series, perhaps in the TIP series. I can do some research
and recommend a sub if you need it, let me know.
BTW Did a fuse or circuit breaker blow? That could be a big clue.