2022-01-17

Applied 5V power. Nothing happened. Measured output of 5V PSU - nothing. I don't know why, though it had been plugged in for ages without drawing current. Disassembled, the fuse is intact.

Replaced PSU with one with 5V output. Measured 5V on bus rails but the fan and LED were off. 5V is getting to the fan, but no rotation. 

Replaced board with second board that I bought. Fan spins. LED D5 does not light, but this is a user LED - it does not indicate any system activity like drive access.

I conclude the first board fan is dead. Fan type is Sunon KDE0502PFB1-8, which is 25 x 25 x 10 mm at 0.9W. Nearest Digikey equivalent is 02510SS-05P-AT-00 for £8.15 or Sunon KDE0502PFB2-8VA.

2022-01-18

Bought a pair of replacement fans, and a PS/2 Y-cable, which arrived the next day.

The fan connectors differ from the original Bergstick style connector, so some modification is needed. No hurry, I shall use the board with the working fan for now.

2022-01-19

I removed the dead fan so I could fit the new fan. Just checking, I applied 5V to the dead fan and it worked! The fan is fixed to the heatsink with some thin sticky foam rubber shaped like a square with a round hole in the middle. I suspect some of it had squashed into the middle, stopping the fan blades from turning. Some fine knife work should fix that.

The 50-way cable now connects to a female DB9 connector.

Ordered various bits for board cabling.