Quieter, Safer, Cooler!
I tried John’s G90 fan mod to replace the small noisy fan at the front of the projector. After doing the mod I was blown away by how much quieter the projector was… unfortunately the G90 was so quite because the SilenX fan was not even spinning!!! It seems the speed sensor in the SilenX fans works differently than in the OEM JapanServo fans. Because of this, the G90 will not always detect when a SilenX fan stops spinning, and the projector may continue to operate without shutting its self down. Thus the projector may continue to run even after a SilenX fan stops working. I only discovered the problem because I lost the picture when the PA board overheated and blew up the high voltage system. This unfortunate event was well documented on both AVS Forum and on CurtPalme.com.
My room has a low 7’8″ ceiling so I really don’t want a hush box making the head room even lower. The only way I have to decrease the noise floor is to make the fans quieter. I wanted this mod to run safe and allow the projector to properly detect if / when the fan stops running so the projector can shut its self down for protection. I decided to use one of the large OEM JapanSevo fans from the back of a G90 for this mod because they are high quality fans that work with the G90 protection system.
The mod I came up with did quite the projector down a lot, but will only work if you have the projector mounted on the ceiling (or if you have a lot of clearance under the projector). For safety’s sake, I also took temperature readings at the PA heat sink after the mod. Surprisingly, I found that with this mod there was actually a 10 degree Fahrenheit decrease in operation temperature. This is good news because most fan mods actually result in the projector running hotter, but this mod cools the projector better than stock.
Basically you need to cut a hole in the bottom of the G90 (top when ceiling mounted) right below the PA board. Started by removing the PA board. Be careful because the PA board holds 200 volts for several hours after the G90 is unplugged. You must wait several hours before pulling the PA board or follow the instructions in the service manual for draining the voltage.
Next, use masking tape to block off any openings between the rest of the G90 cabinet and the PA board cavity. You will be doing drilling and cutting and you must be sure that none of the shavings find their way into the projector. If you get metal dust into your G90… well that would be bad. I also laid a piece of newspaper inside the PA cavity that angled out the front of the projector to encourage the shavings to fall out of the projector rather than to the back of the PA board cavity.
Cutting and Drilling
You will notice there are two guides between the PA board and the G90 cabinet. They must be removed and gotten out of the way. The two guides are held in place by twelve pop rivets. Drill out the rivets and the guides will fall off and into the PA cavity. A word of caution: After removing the PA board guides you must forever remain aware that they are gone. This is important because those guides act to protect the PA board from shorting to the chassis when you remove the PA board. As stated, the PA board holds 200 volts for several hours after the projector is unplugged. So if you pull the PA without it being discharged, the guides are no longer there to help protect it from shorting to the chassis. So if you do this mod, be careful when you remove the PA board!
Once the PA guides are out of the way, trace the shape of your fan onto the bottom of the G90 cabinet. Be mindful that if your mounting system has a brace (as mine in the photo does) that runs between the G90 feet screws, you need to be sure to place your fan far enough forward to avoid it getting in the way of your brace. This large JapanServo fan just barely fit.
Use a jigsaw to cut your fan hole and use a drill to make the four screw holes for mounting the fan.
Clean up all the metal shavings with a vacuum and the carefully remove all your masking tape and newspaper.
Inside the PA board cavity you must do some blocking off of openings to force the air to flow across the PA board and also the PD board. I used aluminum duct tape to to fill the void left by the original small fan enclosure and the main G90 cabinet. I also filled several of the openings between the PA board cavity and the rest of the G90 chassis to improve air flow. Another word of caution; do not block off the openings that allow air to flow from the PA board cavity to the PD board cavity. The PD requires some airflow as well so your mod must allow air to get to both boards!!!
So the original small fan and enclosure must be removed to allow airflow to pass through, and go around the PA board from the bottom. Imagining the airflow further; air enters at the fan and flows from the back of the PA board, past the opening for the original fan. Air then flows across the PA heat sink and also over the PD board. Finally air exits at the front of the PA and PD cavities. Upon further thought, it becomes obvious that you must block off the gap between the PA board and the bottom of the cabinet so that air can’t go around the front of the PA board and circumvent the PA heat sink and the PD board. Here a photo is worth 1,000 words. I used a strip of anti-static foam to block the space between the PA board and bottom of the G90 cabinet.
That’s it. I will probably try adding some small resistors to the positive of this new fan and slow it down a little to make it even quieter. But this is already very quiet and MUCH better than the original.
Craig I. Rounds Chicago IL