I finally had all the fan noise I could stand. I was either going to have to move the radio from the desktop of replace the fan. I decided to replace the fan after recently discovering that there are computer case fans you can buy that come with a thermistor attached to a lead from the fan to control the speed. With one of these I wouldn't have to build any circuitry (PWM, thermistor, etc.) to put in the radio to run a standard PWM fan; Just screw in the new fan, place the thermistor in an appropriate place, and enjoy the quietness.
I looked for a fan that had similar CFM ratings to what was in my Anan and came up with a fan that has very similar specs. The new one actually has more airflow at maximum rpm than the original one does. Here is the one I purchased on Amazon:
https://www.amazon.com/dp/B0037AUS4S?ps ... ct_details
and here is the one that came in my Anan on Mouser:
https://www.mouser.com/ProductDetail/NM ... Rd9A%3D%3D
They are almost identical with the exception that the new one is temperature controlled and runs at about 350 RPM at ambient temperature. Great price too. I paid $8.99 and I see it now is $8.00. My luck.
I powered up the new fan on the bench to make sure it worked (couldn't hear it running!) and made sure it sped up when I heated the termistor with my heat gun. Worked fine. The installation in the Anan is not very difficult. You can replace the original without taking anything out of the Anan case; just remove the front and back covers. You will need some long forceps to reach in and hold the nuts in order to remove/install the screws that hold the fan in. As for the wiring, I just decided to cut it at an appropriate place and splice the plug for the orignal fan to the wiring for the new fan after cutting off the new fans plug. It looked possible to remove the pins from the Anan's plug the original fan uses and desolder/resolder the wires for the new one but since I don't plan on selling this radio I took the easy way out. The new fan is a three pin fan with ground, power, and tach. You don't use the tach wire so just tape it off.
I chose to place the thermistor in the middle of the right side of the case of the radio as near the top as I could get it. This puts the thermistor as close to the finals thermal point as you can easily reach. I decided on this spot after trying three other places; tried rear left side - didn't work, tried right rear side - didn't work, tried right side of case about an inch from rear - worked but thought it would be better closer to the final thermal contacts area.
As for the mounting, I just taped down the thermistor using metal foil tape (used in A/C work) covering the thermistor completely with the tape and sealing it to the chassis. I thought about using heatsink compound on it but due to the small space to get the tape in and attached I thought that might make a mess. Besides, I believe the metal tape on the thermistor which is placed flush against the case should be sufficient to transfer the heat from the case to the thermistor. This tape sticks very well and I don't expect it to come off on its own over time.
I put everything back together, hooked up all the cables, powered it up and..... SILENCE! It was wonderful. But then I wondered if the fan was actually running. I lifted the Anan up so I could see under it and see if the fan was turning and lo and behold it was! This was great. I let the radio run just on receive for about 15 minutes and never heard the fan at all. What a relief!
To test it I set the drive level to 50 watts and pressed tune while listening to see if I could hear the fan speed ramp up. Sure enough, after 60 seconds I started to hear the fan as the case started to warm up. After about 80 seconds I could hear the fan from 2 feet away but it was still very quiet. As soon as I exited Tune, the case temp started dropping and within just a couple of minutes I could no longer hear the fan. Next I simulated using FT8 where I cycled the tune button on/off for 15 second intervals and did it for 15 cycles (I don't run digital modes on the Anan; I use my Icom 7300 for those). The fan sped up to what I assume was full speed. The noise from it was much less than the original fan but I could hear it over the refrigerator (barely). The case temp to the touch was mildly warm. After finishing this test I found I could no longer hear the fan from two feet away after three minutes and it appeared to be back to its lowest RPM sate after about ten minutes as I had to put my ear to the back of the radio to hear it. The case was cool to the touch at this point too.
I'm going to call this a success but will update this post if I run into any problems. Try it, you might like it (but I can't be held responsible if your radio melts down
)!Joe W4WT
