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Author Topic: Eliminate 60 cycle hum from phone connected to Obi  (Read 4347 times)
ProfTech
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Posts: 454


« on: October 03, 2014, 09:32:21 am »

I know this has been discussed lots of times and it mainly applies to Obi 110 but not entirely. Certain phones connected to any Obi may experience a noticeable [even horrible] 60 cycle hum/buzz due to the "Switching" power supply that is included with the Obi. I found a Jameco 120 volt linear 12v regulated supply that works great and eliminated the buzz. Be aware that it costs about $25 dollars, weighs about 1 1/2 lbs and pulls about 22 watts so won't run cheap. But it does fix the hum problem. Several numbers on the box "Part number 170245", "PWS-37-ACDC", & "DDU120100H4480". I ordered mine from AttBatt.com under the DDU number.
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dircom
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Posts: 464


« Reply #1 on: October 03, 2014, 09:57:36 am »

I wonder if a 12V UPS battery would work?
I have a spare UPS I might try it, just need to recharge it occasionally
bonus no 24x7 energy usage waste, and no power surges
isolation from A/C power
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ProfTech
Sr. Member
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Posts: 454


« Reply #2 on: October 03, 2014, 10:12:51 am »

I considered using a battery but didn't have anything to try. Should work fine except I wasn't sure of a good / inexpensive way to keep it charged. I figured a small battery should run the Obi 1 to 2 days but as the voltage drops you might have an issue if it goes below (unknown number). I used a Netgear supply for a few days that was better but its voltage was 14v or a little more so wasn't sure if that was a good idea. Didn't smoke the Obi but I took it off anyway. I'm considering putting the Jameco on a simple timer and shutting it down from 10PM to 8AM. Side benefit no bogus calls after 10 PM! I also tried a standard 110v UPS but I was running the Obi off the "Filtered" side because I didn't have a battery. Still heard the buzz and they want about $60 for a battery for this UPS.  Sad
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dircom
Sr. Member
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Posts: 464


« Reply #3 on: October 03, 2014, 10:15:08 am »

I forgot, I picked up a couple of what looks to be wheelchair batteries at a thrift store.  Will hook one up, and periodically test voltage drop
but I would need to add a switching step up/step down dc/dc power regulator
« Last Edit: October 04, 2014, 05:11:38 am by dircom » Logged
SteveInWA
Hero Member & Beta Tester
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Posts: 5787



« Reply #4 on: October 03, 2014, 05:49:49 pm »

Why not buy it directly from Jameco for $14.95?  You got robbed.

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?search_type=jamecoall&catalogId=10001&freeText=DDU120100H4480&langId=-1&productId=170245&storeId=10001&ddkey=http:StoreCatalogDrillDownView
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--Steve

Google Voice Forum Product Expert

https://support.google.com/voice/community
ProfTech
Sr. Member
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Posts: 454


« Reply #5 on: October 03, 2014, 06:33:41 pm »

I checked [after the fact] and the shipping was almost twice as much through Jameco. Ended up about a dollar cheaper from AttBatt. YMMV
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SteveInWA
Hero Member & Beta Tester
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Posts: 5787



« Reply #6 on: October 03, 2014, 07:19:11 pm »

I guess the shipping fee for the hunk of transformer iron is almost as much as it's worth.   Roll Eyes

But seriously, there's nothing like a good old IC-regulated, filtered, linear power supply.  A properly-designed switching PS should have also included sufficient isolation and bypass capacitor filtering, but I guess it's race to the bottom commodity part these days.

It would have been interesting to try an equivalent switching PS from Jameco to see if just changing manufacturers would have made a difference.

I've had very good experience with their power supply product line myself.
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--Steve

Google Voice Forum Product Expert

https://support.google.com/voice/community
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