9401-P03

First (main CPU?) board

Second (IOP?) board — note the 68EC020-16 processor in the lower right, and the 80286-10 processor in the lower left corner

The IBM AS/400 9401 Model P03 is a comparatively tiny model. It's still a CISC processor machine, despite having a black case.

Tweaks

There's not much physical space to lessen its noise emissions by applying dampening pads to the case, or stuffing with noise absorbing material. A little relief can be achieved by disassembling it completely to extract the PSU. You need to drill out the rivets and search for some matching screws in your collection. The fan can be made a bit less noisy with a 27 Ω resistor put in series. Don't expect wonders, though.

Note! 33 Ω or higher values trigger some fan observing circuitry on the PSU board. If it triggers, you'll get the amber LED on front and a SRC 00000003 in the display, after the PSU shut down. This happens within the first few seconds of power on.

The original fan fas ball bearings but for unknown reasons, the visible bearing emitted an awful rattling noise. Removing the sticker showed dark smear. Using solvent, I finally could identify this as grease-rust mixture. Since I couldn't remove the snap ring keeping the rotating part of the fan in place, I could not access the inner bearing and chose to exchange the 92 mm fan with a newer, high-quality model with also 25 mm thickness. The machine is much quieter now, even without a resistor. Note, this is a major undertaking. It requires time, patience and creativity because of the way the fan has been locked in place through bent parts of the PSU case.

Weblinks

• IBM Application System/400 Advanced Portable Models Sales Manual, IBM
• IBM AS/400 9401 Portable (Model P03), supervinx.com
• IBM AS/400 9401 Portable (Model P03) with InfoWindow II, supervinx.com