Loud buzz on OBi110 line PSTN
Jon9999:
OK, voltage tests! (And I didn't get electrocuted!) (And Shale, I was never worried about damaging the meter -- I was worried about dying. :o )
DC tests (red probe on the jack, black probe in the ground hole of an electric socket):
TELCO LINE 1 (the one that OBi was on):
wire ON HOOK OFF HOOK ringing
----- ----------- --------- ----------------
RED -0.4 VDC -20.5 VDC +0.1 to -2.1 VDC
GREEN -51.6 VDC -29.1 VDC -48.0 to -60.8 VDC
----- ----------- --------- ----------------
TELCO LINE 2 (the one that bypassed OBi):
wire ON HOOK OFF HOOK ringing
----- ----------- --------- ----------------
BLACK -0.1 VDC -20.4 VDC 0.0 to -2.1 VDC
YELLOW -51.7 VDC -29.2 VDC -48.1 to -58.9 VDC [added off hook since original post]
----- ----------- --------- ----------------
AC tests (red probe on the jack, black probe in the ground hole of an electric socket):
TELCO LINE 1 (the one that OBi was on):
wire not ringing ringing
----- ----------- ----------------
RED 0.3 VAC 1.5 VAC
GREEN 0.2 VAC 91.0 VAC
----- ----------- ----------------
TELCO LINE 2 (the one that bypassed OBi):
wire not ringing ringing
----- ----------- ----------------
BLACK 0.4 VAC 0.8 VAC
YELLOW 0.2 VAC 91.4 VAC [corrected from original post]
----- ----------- ----------------
Jon9999:
I just noticed one thing, which I don't know whether it's normal or the problem.
I re-tested all the wires with the connected phone off-hook (not ringing). I notice that the DC voltages changed considerably by 20-30 V compared to on-hook as reported above. I've added the new observations to the original table above. The AC voltages seemed to spike a tiny bit (a few volts) when I first took the phone off-hook, but then they settled back down pretty quickly at the same on-hook voltages.
I also tried looking at the voltages on Line 2 while taking Line 1 off- and on-hook (and vice-versa), and there was no effect. I also tried looking at the voltages on Line 2 when Line 1 was ringing (and vice-versa), and there was no effect.
Shale:
I have to congratulate you on your testing and reporting. Marking VAC or VDC for reading could be an improvement, but I don't think that will show anything significant. I see nothing abnormal in your measurements, unfortunately. Just check that your OBi power supply has 2 prongs and not 3 where you plug into the wall or outlet strip.
One thing that does hit me is that do you have a remote door lock control or buzzer or something shared with line 1? Maybe moving the OBi to line 2 would be a good idea in that case. Even then, I don't know what would cause your continual buzzing.
_____ _____
| R | | B |===TO LIVING RM JACK (L1)
TELCO/LINE 1 (R/G)---| J | /--(R/G=L2)---[OBi]---\ | |===TO BEDROOM JACK (L1/L2)
TELCO/LINE 2 (Y/B)---| 1 |==SPLITTER< >SPLITTER==| U |===TO KITCHEN JACK (L1/L2)
| 1 | \ / | |===TO OFFICE JACK (L1/L2)
~~~~~ \--(R/G=L1)---------/ | S |===TO DINING RM JACK (L1)
~~~~~
<----NID--------> <---------------MEDIA CLOSET---------------------------> <---REST OF HOUSE---->
One further test comes to mind. Before a possible shipping back your third fried OBi, try it on a phone line at a different location. Maybe it is not frying the OBi, but that at some point your doorbell system puts a kind of interference (look up "common mode" if you are wondering what I am envisioning) on the wires that your phone rejects but the OBi does not sufficiently. The big flaw in this is why would the interference not be there at the beginning, but always be there for the same OBi110 even though you plugged and unplugged several times This is a strange situation, so I am coming up with weird ideas.
Quote from: Jon9999 on July 24, 2013, 10:01:23 am
I just noticed one thing, which I don't know whether it's normal or the problem.
I re-tested all the wires with the connected phone off-hook (not ringing). I notice that the DC voltages changed considerably by 20-30 V compared to on-hook as reported above. I've added the new observations to the original table above. The AC voltages seemed to spike a tiny bit (a few volts) when I first took the phone off-hook, but then they settled back down pretty quickly at the same on-hook voltages.
I also tried looking at the voltages on Line 2 while taking Line 1 off- and on-hook (and vice-versa), and there was no effect. I also tried looking at the voltages on Line 2 when Line 1 was ringing (and vice-versa), and there was no effect.
It is normal for the off-hook voltage to drop, although the voltage usually drops by a lot more than what you are observing. Off hook voltages that I have seen have all been less than 15 volts across an off-hook phone line. I will do some looking to see what this might indicate. It may be normal.
Jon9999:
Thanks, Shale. There's no doorbell or other service on either line -- just POTS. The only difference between L1 and L2 is that L1 has Distinctive Ring service, so when it rings, it rings with a different pattern than L2. But it's a US telco-standard (Verizon) ring. Both lines have Call Waiting, Caller ID, and all that -- but no other kind of other input from the outside, not even DSL service. On the inside, I do have a fax machine on L1 and not L2, but I don't think the problem is coming from the inside as I said previously because the damage (if it really is electrical damage) is on the OBi jack that faces the outside.
I'll add "VAC" and "VDC" respectively above.
Jon9999:
Quote from: Shale on July 24, 2013, 10:05:46 am
It is normal for the off-hook voltage to drop, although the voltage usually drops by a lot more than what you are observing. Off hook voltages that I have seen have all been less than 15 volts across an off-hook phone line. I will do some looking to see what this might indicate. It may be normal.
The voltages I reported above were DC from the phone wire to ground. So the voltage across the line would be the difference between red-to-ground and green-to-ground, for example, which is indeed less than 15 volts (8.6 V). That's right, right?
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