For what it's worth, at this late date on this thread, I'm pretty sure I've hit this problem and so have ordered a fan from here:
http://www.northwesttechnical.com/in...4c96d777d0f7b4
Snap Server 4100 CPU Fan
* 12VDC @ 0.10A
* 50mm x 10.4mm
* Various Manufactures
OEM (NWTEC) Part Number: SS4100CPUFAN
This has been a great forum and thanks again for help. Thanks to you I have another old 4100 that is still faithfully coughing up data.
MM