The 120mm cooling fan in the back box of my Data East Star Trek 25th Anniversary is getting noisy, and I was thinking of replacing it. I couldn't find any info in the manual on specs for the fan, which looks to be pretty standard 12v type as found in computer cases.

I found a fan with these specs, which look pretty middle of the road in terms of air flow (CFM), and thought it would be a likely candidate for the job:

Dimensions 120x120x25mm.
Bearing Two Ball bearing
Rated speed 2400RPM
Noise level 35.0 dBA
Air flow 78.34 CFM 2400 RPM
Current A 0.25 A
Life Hours 70.000

Any comments? I wouldn't have thought there was too much to worry about with a replacement of this nature, but thought it was worth asking anyway...

The cooling of the back box is not that difficult... the heat producing electronic components are not that tightly packed in there compared to, say, a computer case.

So I'm not overly concerned about a massive air flow to maximise cooling efficiency. Actually, the reason I'm replacing the fan is mostly because it's noisy, and it's getting a bit annoying.

There is a trade-off between air flow rates and sound produced anyway. If you want a really quiet fan you have to be prepared to compromise on cooling efficiency. Having said that, cooler is better for the longevity of PCBs. Components may be rated to operate at high temps, but the repeated heating and cooling of the boards will lead to stress and failures more quickly than boards that are subject to less thermal stress. So, yes, the boards are designed and rated to operate at fairly high temps, but all things being equal, cooler is still better.

Finally, a good reason to use ball bearing fans instead of the cheaper sleeve bearing type is because as they wear out, they get noisier (like the one I'm replacing). The sleeve bearing type will often sieze up and fail silently, which means that you might not even be aware you have a heating problem. I had a computer that this once happened to with the fan in the power supply, leading eventually to the failure of the entire power supply unit. So although they do last longer, the reason ball bearing fans are good is because they are noisier_, not quieter, than the sleeve bearing type (at least once they've started to wear.)

Anyway, in the absence of any definitive specification in the service manual, I've ordered a replacement unit with both a moderate air flow rating and dB level rating. I made a point of buying it from the USA rather than locally (because the local Oz economy is doing so well, I feel it is better to support the "little guy" retailers in the US and UK economies wherever possible.)

And even with shipping from the US, the price of the unit worked out about the same as I'd pay in a local computer shop here. Weird...