[TenTec] Hercules II fan noise

[Steve Hunt]

Today I did a few checks on the present fan.

1) I unbolted it from the under-tray and held it in place by hand. There 
was no reduction in noise, so I don't think resilient mountings will help.

2) I removed the fan completely and ran it on the bench from an external 
PSU. It was a little quieter, but not by much.

3) I tried a small amount of lubrication but that made no difference.

4) One thing that made a surprising difference was the presence or 
absence of the "finger guard". In fact anything close to the fan and in 
the intake airflow made quite a difference to the noise level. Just 
holding a pencil across the intake brought the level up noticeably.

5) Surprisingly there was very little dust around the fan or the heatsinks.

I've managed to locate a new fan that seems to have an equivalent spec - 
it should be here in a few days, and hopefully will solve the problem.

I wasn't too impressed by Ten Tec's thermal engineering. The fan is on 
the underside of a central chassis plate, and the PA transistor heat 
sinks are the other side. There are just a couple of very small holes in 
the plate where the air can flow from the fan side through to the 
heatsink side!

73,
Steve G3TXQ