Loud buzz on OBi110 line PSTN
Shale:
Quote from: Jon9999 on July 24, 2013, 01:35:00 pm
Sigh.
One last question before I bite the bullet and plug the new OBi back in: Could it have something to do with Call Waiting? What happens, voltage-wise, then a CW signal comes through? Is it like a ring, with high-voltage AC? Could this be something that might damage the OBi? I tried testing with the voltmeter, but I couldn't coordinate getting the voltmeter on the contacts at the same moment that the beep came through.
Since 100 vac is normal ringing, the Line input to the OBi should be robust.
Call waiting is not a high-voltage event. There may or may not be momentary reversal of the polarity on the two phone wires, but no ringing voltage is involved.
I have another off-the-wall thought. There are a lot of old DSL filters sitting in people's drawers. I wonder if this might have some minor protective properties if placed between the OBi and the phone line. It is just a low-pass filter that passes frequencies less than 15 kHz. But it might add a little impedance to keep some mystery surge from doing damage. Getting OBi involved sounds useful. They might have some insight.
Jon9999:
OK, gentlemen, I've connected the new (#3) OBi110. I put a 2-line splitter onto the NID itself and hooked the LINE port of the OBi directly into the Line 1 half of the splitter, right there at the NID, placing only a telephone surge protector in between. I hooked the PHONE port of the OBi directly into a stand-alone phone (it's a cordless one -- sorry, I don't have an old phone on hand that doesn't need to be plugged in). Both the OBi and the cordless phone are plugged into a surge protector that has built-in indicator lights showing that the AC circuit and grounding are OK. I'll let it cook a while and will report back. If it survives the night, I'll move the OBi into the media closet first, and finally I'll isolate both the PHONE and LINE ports with phone surge protectors before connecting the PHONE side back into the bus that connects to the rest of my phones.
Jon9999:
24 hours in, with heavy use... So far, so good.
I've added a DSL filter between the NID and the LINE port, as Shale recommended earlier, in addition to the surge protector, as a "belt-and-suspenders" thing. (I don't have DSL service.)
I still haven't had the courage to connect the PHONE port to the rest of my internal phone network. It's still hooked up directly to just one cordless phone base, but I do have the first 2-line splitter between the NID and the LINE port (actually, between the DSL filter and the line port).
NID==[DSLFILTER]==<splitter>--<surgeprot>--[LINEPORT]OBi110[PHONEPORT]--(cordlessphone)
I think I'll give it another couple of days and then bite the bullet. I'll leave the DSL filter and the surge protector on the LINE side, and I'll add another DSL filter and surge protector on the PHONE side too before running back into the 2nd splitter and thence into the internal phone network bus.
NID==[DSLFILTER]==<surgeprot>--<splitter>--[LINEPORT]OBi110[PHONEPORT]--[DSLFILTER]--<unsplitter>==<surgeprot>==NETWORKBUS
Any other thoughts before I do this?
Unofficially: Do any of you have any thoughts on whether there is any chance at all that the problem came into the OBi from the PHONE side, since the effect (damage?) seems to have been solely on the LINE port? Can you see any way that hooking the PHONE side back into my phone network would have been the source of the problem? I'm sort of thinking that whatever happened must have come from the PHONE side, so I should be out of the woods. Right? (Why don't I believe myself?)
SteveInWA:
With regard to your question about the LINE side vs the PHONE: You didn't have Verizon come out and inspect/confirm that your NID is properly grounded. Without doing that, you can't be sure that some voltage surge/spike/lightening strike might damage your OBi, your attached phones, and/or yourself. If some other part of your house phone wiring (what you've been calling the "bus") is somehow carrying voltage it shouldn't be (as I discussed, via a damaged spot of wiring touching AC), you can create a path for current to flow. You want that current to flow to ground instead of into your equipment or into you. I'm just repeating this as a disclaimer.
That said, make sure you don't have a wiring error on your "bus", such that your jacks are still carrying your L1 signal from the NID. If so, and you plug in the OBi's PHONE jack into your bus, and the Verizon POTS L1 line rings, it'll send the 100+ VAC into the OBi's PHONE side and may fry it. The only way to be sure of this is to plug in a known-working, single line phone, into a jack on your bus and make sure it is dead, or use a tester.
Keep in mind that there are two types of RJ-11 splitters, that can look identical to the casual observer. One kind simply duplicates all 4 conductors on every jack, and the other kind breaks out L1 and L2. Be SURE you have the right kind, or you will be feeding L2 back into L1 or vice versa.
If you don't already have them, I'd strongly suggest buying two items of test equipment: an AC outlet tester (a plastic plug with LEDs on it, that show properly wired outlets vs. reversed polarity or bad ground), and a phone jack tester (a plastic dongle with LEDs on it, that shows live phone lines, reversed polarity, or dead lines). The first is available at any hardware or home warehouse store. The second used to be at Radio Shack, but seems to be gone. You can still find them online, for example:
http://www.amazon.com/Gardner-Bender-TT6200L-Phone-Tester/dp/B000GL95JA
Jon9999:
You know, I've been thinking. Maybe it's wrong to hook the OBi in serial between my PSTN line and my internal phone network. Is it within the unit's design parameters to be used that way? Or should I perhaps connect the OBi on its own, isolated branch of my phone network, coming off a 2-way splitter at the NID, with its own separate telephone instrument? I know that means I'll have to use that particular phone when making a GV or SIP call and I won't be able to "flash" into the OBi from my other phones to do transfers, etc., but at least I'll be able to use OBiON, which is really the main point for me. It would be a trade-off, but maybe worth it if it means the unit won't fry again.
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