More progress.
I brought out my old Tunze 3155 ATO and cleaned it up. Still needs testing.
I also brought up my old ATI 36 inch Sunpower for testing. Once I plugged it in I realized I would never be happy with those old fans. Crusty and dirty they resisted cleaning and seemed louder than I remembered. On the plus side all 6 old bulbs lit up and functioned.
As you can see from the pics the fan are dirty. This led me to start searching for a quieter fan to replace them. Geez.. this is an odd size. 60x60x10mm. Not a PC mod enthusiast size at all. In other words do not waste your time searching for a silent after market fan. They do not exist.
What you can do though is search all the existing brands and find the fan that seems like a good choice based on CFM, dBm, RPM, etc...
Here is a link to the existing fan. I used digikey's website for accurate info, not the best pricing.
https://www.digikey.com/product-detail/en/delta-electronics/EFB0612MA/603-1407-ND/2560531
Here is a link to what I replaced it with:
https://www.digikey.com/product-detail/en/mechatronics-fan-group/MB6010M12B-RSR/1570-1116-ND/5209813
While this fan has less CFM and RPM it is significantly quieter dBm wise. Delta is 29 versus 22.5 for the Mechatronics.
This is what I am thinking. No one runs the Delta fans at 12 volts. 4.5, 6, 7.5, and 9 are the most common people mention. I used to run at 6 or 7.5. I have AC in my house which helps with ambient air cooling.
This fan may very well move less air but be quieter at higher voltages. So I could just run it at 7.5, forget about it, and have a quieter setup. Maybe even 9 volts would be less noise than a Delta fan at 4.5 to 6 volts.
Let's give it a try.
For the life of me I could not get the fan apart from the metal ATI cover without cutting the rubber grommets. So I cut two of them careful with a an exacto knife and this is what I am left with.
Now notice I have two grommets left that are in good shape but the bottom is trimmed a bit at the factory. This is a key thing. We can use those to remount it and the leftover pieces can be the vibration bumpers for the other holes. As I was taking it apart and cutting I thought I would have to buy more.
This pic shows how I started the whole process.
Next goes the large washer.
Next goes the fan and the tricky part is squishing it through since the part you normally pull has been clipped. Just pull it out enough for the rubber to catch one edge of the fan and leave the rest inside. It is quite a tight fit and holds it very firmly. No need to use the smaller washers. Save them just in case but a cheapo home depot part if needed due to this idea failing over time.
This pic shows both new fans mounted. A side shot and a bottom shot. I am not joking when I say they are firmly mounted. Not as good as the factory but more than reasonable for this application. No need to buy new rubber grommets.
Now mounted back and running.
Soooo... right away I can tell the fans are quieter than my old dirty ones. Big difference.
At 12 volts they are loud. Not as loud as Delta but loud.
At 9 volts not that bad. I was pleased. They are definitely an upgrade.
At 7.5 volts they became decent. I can live with that.
At 6 volts one could almost say reasonably quiet with normal background noise going on. Let's face it. A fan this small will never be totally silent due to physics. Just not sure at 6 volts they will move enough air.
4.5 volts. Barely hear it. What I consider quiet.
I will update my thoughts on the noise once I leave them running for a few days to a week to break in.
I am at the point I will sacrifice some PAR for a quieter tank and still be able to use T5.