Ampro Resource

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.

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.

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.

Well, done for now at least. After watching several movies on it, I believe that its pretty stable.

The highest runtime temperature I remember seeing was 32.3C — which isn’t bad. It usually manages to say within 10C of the room temperature. I’m fairly satisfied this is ‘safe’.

The other two fans are really causing a racket at this point (relatively). So I’ve moved the temperature probe and will probably swap those fans real soon now. I put my probe near the registration board above the green CRT. This should be one of the ‘hot’ spots in the unit — since it is at the ‘top’ of the enclosure.

I believe the internal temperature stayed around 30C.