Join Date: Aug 2001
Location: escaped Silicon Valley
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Oh boy, the fan saga continues...
I could still hear the droning noise even with the rebuilt Nidec fan installed, so that points to one of the other fans. I spent 2 hours disassembling half the projector to remove all 4 fans for cleaning and testing. Surprisingly the dirtiest fan was the large squirrel cage fan that blows filtered air into the optical block.
All 4 fans tested fine on the bench, but the large squirrel cage fan had a faint crackling sound. I replaced both bearings in the fan (same as in post above), but it still makes the same noise. Since it's not mechanical, it could be failing electronics or an intermittent short in a coil winding. I couldn't find any markings to identify the fan--closest was the circuit board inside was labeled Mitsumi. Original JVC part number QAR0446-001 is replaced by QAR0526-001 and costs about $130 with shipping. I'll just use the original until it fails completely.
Long story short, I reassembled everything but put the Delta fan back in (I use an OSRAM bulb that runs hotter and want the extra airflow for more margin). Now there is no more droning sound or any type of vibration noise--just airflow noise. Reseating all the fans must have eliminated the vibration.