12-25-2015 8:56 PM
My AT&T DPH-151 MicroCell started making a buzzing sound. It almost sounds like there is a small fan in there that has bearings that are on their way to failing. However, I'm not aware of a fan being in there - does anyone know? If not the fan, there must be some component that is vibrating at audio frequencies - probably not a good sign. The Microcell still functions normally for wireless calls. Any ideas?
Solved by: Go to Solution.
12-25-2015 9:51 PM
There are no moving parts in the MicroCell. If you hear a buzzing sound that is not good. It could be one of the radios. You may want to plan on eventually replacing the MicroCell down the road because they can't be repaired and you are out of warranty. I've had a DPH-151 for years and took it offline when I got the new DPH-154, but there were no sounds or issues with the 151.
12-26-2015 10:20 AM
Buzzing sounds from a PCB with no moving parts are typically caused by capacitors or perhaps a transformer. Reviewing breakdown pictures of the Mcell PCB shows at least 7 capacitors but no transformer so without further information, one would suspect one of the caps is going bad. One way to verify this would be to open up the Mcell case to see if any of the caps have a bulging top. Doing so would trigger the anti-tamper jumpers which would render the Mcell inoperative, so that isn't an option.
The Mcell is operating at the moment but if it is a bad cap then it's only a matter of time before the Mcell fails. If you are not a candidate for WiFi Calling, then you will have to purchase another Mcell.
I am not an AT&T employee.
12-26-2015 10:32 AM
02-10-2016 9:13 PM
The problem was due to a bad power supply which eventually failed completely. It was a 12 volt, 1.25 amp supply provided by ATT/Cisco with the Microcell. I happened to have a 2 amp, 12 volt supply with the same power plug. I plugged it in and the Microcell now works fine, without making any noise.
I'm guessing that the noise was coming from the bad supply varying its output at audio frequencies and the circuitry in the Microcell converting it to sound waves via microphonic effects.
02-10-2016 9:50 PM
The MicroCell's are a bit finicky with their power so it would be best to replace the ac adapter with one of the same rating as the original one. Your assumption about the noise is probably correct. You can check the adapter by using a voltmeter. It should read 16VDC with no load.
03-21-2016 4:13 PM
I would not recommend a power adapter like the one that came with the Microcell. It is probably just an unregulated wall wart. The service specs for it indicate 16V no load, 12V with specified load. It is probably just a transformer, diodes, and a filter capacitor. I replaced it with a regulated 12 volt, 2 amp regulated supply. The Microcell has been working fine ever since I replaced the supply.