IR100 Back Rotation
The IR100 suffers from speaker hum due to the transform(er) interfering with the speaker. Its not surprising if one puts a transform(er) right next to a speaker's coil.
Looking at the back of an IR100, its is fairly obvious that its been put on the wrong way round. The bass-reflex port should be into the rear of the speaker; its beautifully moulded to interface with the rear of the speaker magnet.
The question is why it was assembled this way ? Best guess is that putting the transform(er) behind the radio module meant that the WiFi dongle didn't get much signal. Plus, the clearance on the analogue boards (attached to back of radio) is a bit tight on the speaker.
Rotating the back will fix the hum problem, but its usually only undertaken along with moving the WiFi dongle, see Installing an External USB Socket on the IR100 and Moving the USB Wi-Fi dongle on the IR100.
To change the back round:
- Remove six rear fixing screws
- Carefully slide back from radio
- With chisel (or similar) remove wooden block glued to bottom edge of case (lower centre fixing screw).
- Rotate the back 180 degrees.
- Check the heat-sinks on the analogue boards do not foul the speaker coil; make slight bend changes to the heatsinks if necessary.
- Refit four corner fixing screws (two screws no longer work as nothing to attach to).