Got a Mirage mx-36HP3 on the desk today. Board number EPT-DX2912Z.
Issue:
Transmit audio has constant oscillation sound, sounds like background air noise and can't be brought down with mic gain off.
Evaluation:
Q39 looked burnt under it on the board.
Removed Q39 and noticed it's the wrong part. The part someone put in that spot is a 2SC2076 fet, but normally that limiter is a 2SC945. This would explain the burnt spot on the board under it. Put the 2SC2076 in the tester and it tested fine as a BJT with an Hfe of around 120.
Anyone ever heard of switching the limiter (C945) to a different transistor? If so, what's the purpose?
Gonna place a 945 in there and try it out.
Issue:
Transmit audio has constant oscillation sound, sounds like background air noise and can't be brought down with mic gain off.
Evaluation:
Q39 looked burnt under it on the board.
Removed Q39 and noticed it's the wrong part. The part someone put in that spot is a 2SC2076 fet, but normally that limiter is a 2SC945. This would explain the burnt spot on the board under it. Put the 2SC2076 in the tester and it tested fine as a BJT with an Hfe of around 120.
Anyone ever heard of switching the limiter (C945) to a different transistor? If so, what's the purpose?
Gonna place a 945 in there and try it out.