Silenced!

Picked up some 120 Ohm 2W resistors and installed them inline with the fans. This effectively dropped the power to the fans from 20V down to about 12V. They run almost silently now (as designed) since they are intended to run at 12V being PC case fans.

There is something almost magical about having the projector be so quiet. If you get close to the fans, you can hear a gentle ‘whoosh’ sound – but that’s it. Not enough to intrude on the movie at all.

We watched Austin Powers (the original) — I checked the temperature during the movie a few times. After running for 2 and a half hours (there was some amount of warm-up) — the internal temperature was only 5C higher than it was with the original fans. Safe enough for me.

I’ll keep monitoring the temperature(s) to see that its stable. I’m sure that once I ceilnig mount the projector things will change a little as well.

The next modification will likely be some HVPS maintenance and possibly the addition of a fan to help keep it cool.

I’m also anxious to get my setup more stable, as I’ve been moving things around so much the setup isn’t all that great. The convergence drifts more than I’d like — and my mechanical setup is off at the moment. Always things to do..

Noisy fans revisited

Well, turns out that the fans in the Ampro 4000G are powered with 20V. This of course causes the ‘quiet’ vantec fans to run much faster than they would from 12V.

I tried connecting them in serial, effectively giving each fan 10V. They are much quieter, but had a ‘beat’ sound that was sort of annoying. I suspect that this was too low to run them and get them to run smoothly. They may have been causing interference with each other as well.

Having picked up some 47Ohm 1W resistors today, I tried using them to slow the fans down. The down side to this is that I’m creating heat to slow the fans down. Using one 47Ohm resistor cuts the noise quite a bit, but its still too loud for me. I used 2 in series, effectively doubling to 94Ohms. This was quite a bit better, but not ‘silent’. This should have been roughly the equivalent of 14V.

In theory, I need 133Ohm resistor to bring them down to 12V. I’ll have to take another trip to the electronics store.

It seems quite a bit of the noise is due to the mounting of the fans as well. I’ve removed the grills entirely, so there isn’t too much turbulance, but the case seems to vibrate quite a bit from the motion of the fans. I may look into ways to isolate the fans from the case, or dampen the case. Possibly both.

While I was writing this up, I realized that if I used 3x the 47Ohm resistors, I’d be pretty close to 133Ohms. So I ran downstairs to give it a shot. The fan is pretty much silent at this speed. I can’t comment on the ‘beat’ sound since I only have 1 fan running — but interestingly I was attributing a buzz sound to the fan, when it is in fact the long circuit board that runs next to the blue tube. I proved this by running with no fans.

I’m tempted to try using 2 of the 47Ohm resistors in series to slow the fans down to something close to their proper speed, and see how things work out in terms of airflow & cooling.

Two fans replaced

I finally got around to replacing the last 2 fans in the projector. I also removed the filters & grills to increase airflow.

Now with the projector running you can feel air being pushed through the unit — there is more airflow. This is also indicated by a lower running temperature, it was 5C lower with the new fans.

The problem is, they are still too loud. 🙁

I’m going to put a resistor in the power line to slow the fans down. This should further reduce the speed (and noise) of the fans. I need to also check what the power being supplied to the fans actually is. I have read somewhere else that its 20V, not 12V. This may make a difference in the performance of these fans — they certainly are not a ‘quiet’ as the PC Power and Cooling “Silencer” fans I’ve used in the past for my old ECP and they are rated almost the same.

Either way, I’m not satisfied yet — we’ll just have to see what else can do. Opening up the vent holes at the back of the projector may also be something worth doing to increase airflow through the unit.

New server!

I finally got around to replacing the Pentium 90 with 32MB of RAM with a ‘real’ machine. This site should now run much smoother.

The home theater has also had a shuffle to move it around in the basement to where it will eventually be once we put some walls up (the joys of an unfinished basement).

Between rebuilding the server and shuffling the theater, I haven’t had much time to attack those fans. However, their days are numbered.