Cooling an Overheating Ampro

Having problems with an overheating Ampro?  Read on!

The following procedure and pictures were provided by Mike McFaul.  Thanks Mike! 

My projector (Ampro 3600) developed a temperature problem. When it got hot sometimes my registration board would go funny. The moment I raised the lid (it's floor mounted), the board would cool off and start working. Finally I started to isolate the problem down to a few chips.

While waiting for a replacement board from Curt (thanks, eh!), I decided to attempt to do something about the overheating part! I soon realized that when the lid was up, the projector itself ran a lot cooler, not just the area where my board problem was.

On closer inspection, I realized that the projector is a pressurized system, two fans on the bottom and two fans on the top blow air into the projector body. The power supply fan just cools the power supply, as that is a closed box in the projector. There are two problems with this setup:

So I decided to try to do something about that. The first try was an air intake for the power supply (see Figure 1 below); it lowered the power supply temperature by almost 5C! But it did not affect the internal temps of the projector.

Figure 1: Power supply air intake to stop hot air from recirculating

Next I worked on making sure that the two upper fans did not draw in the hot air coming off the two heat sinks (focus modulator board [really hot], and the registration amplifier board). I baffled the hot air to exit the projector over the lenses out front (see Figure 2 below).

Figure 2: Baffle to force hot air to exit the projector over the lenses out front

I then worked on making sure hot air from the rear of the projector didn't get back into the area under the lid and so wouldn't be drawn back into the projector (see Figure 3 below).

Figure 3: Baffle to stop hot air from the rear from re-entering the projector

The air for those two fans now comes from the sides of the case, next to the red and blue tubes. I attempted to make sure the hot air exiting over the lenses did not mix with the cooler air by directing it mostly over the middle of the projector (see Figure 4 below) (the final angling of the front parts of the side baffles is right over the bolts anchoring the lenses).

Figure 4: Ensuring hot air exiting over lenses does not mix with cooler air by directing over the middle of the projector

This work lowered the internal projector temps by about 4.5C. The area over the registration board dropped by a little more than 5C. Now my projector runs cooler, and my registration board isn't acting up!

The baffles are made from 2 layer cardboard with weather stripping applied to the top so when the lid is closed, they seal air tight to the lid.

The table below summarizes my temperature findings. All temps in Celsius and are averages over a couple of readings. The 'Ambient Temp' is the air temp in the room. The 'Temp Probe' is a measure of the air temp right between the two fans on the top:

I hope this might help someone else with a temperature problem...

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