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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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Telephone Disconects on First Ring
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Is it only this phone? Have you tried a different phone?
Richard |
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My telephone disconects on the first ring.
Sometimes it's the second or third ring, but it's shorting out on the ring. What usualy causes this? so that I can fix i Wayne- The ringing voltage from the phone company is about 90 volts peak-to-peak, probably a square wave. There is a DC voltage on the line from batteries at the phone company, often 48 volts DC positive ground. From your brief description, it sounds like something in the phone can't withstand the peak voltage and breaks down. When that happens, the phone company's equipment senses the DC current and reacts as if the phone had been answered. However, when the ringing stops, the weak part stops conducting as if the phone had been hung-up. It is possible that the phone was damaged by lightning striking a telephone pole. Look for burnt spots on the phone's circuit board. There may be a diode bridge used to ensure correct voltage polarity, that has a bad diode. There may be a capacitor across the line that has too low a breakdown voltage. Unless you can isolate the weak part(s), a new phone is in order. Fred |
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Wayne posted:
My telephone disconects on the first ring. Sometimes it's the second or third ring, but it's shorting out on the ring. What usualy causes this? so that I can fix it. Many things can cause it, including telco trouble. The first thing you should look at on your side of the Network Interface is: How many ringer equivalents (REN) do you have on the line? Too many can trip the ring, especially if you are on a long line from the Central Office. Don |
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Others here have provided good reasons for your failure.
Now start by breaking the problem into parts. Take a simple POTS phone to your NID. Open that 'premise interface' box. Unplug the wire going inside your house. Connect phone directly to that box. Conduct the ringing test. Now we have important facts to further solve the problem. "WayneSallee.com" wrote: My telephone disconects on the first ring. Sometimes it's the second or third ring, but it's shorting out on the ring. What usualy causes this? so that I can fix it. |
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AOL is really getting discusting. My postings have not been properly coming through lately. So I had to come to google to read the posts. But anyway enouph about pathetic aol: I tryed the REN factor by diconecting other lines to reduce the REN. But sill it's the phone. When the phone does it speraticaly, it makes testig more dificult. The speraticness is probably caused by capasitors charching or discharging, making a slight difference in how the phone hadles the situation. Wayne Sallee Many things can cause it, including telco trouble. The first thing you should look at on your side of the Network Interface is: How many ringer equivalents (REN) do you have on the line? Too many can trip the ring, especially if you are on a long line from the Central Office. Don |
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What's the best way to locate the ringer circuit?
Wayne Sallee Franc Zabkar wrote: Disable your phone's ringer circuit by desoldering one pin of the 1uF or 0.47uF 250VAC cap in that area. Call the phone using your mobile. You won't hear it ring, but if your phone stays alive, then the problem is somewhere in its ringer circuit, probably a "ring detect" IC. These ICs contain the bridge rectifier alluded to in my other post. - Franc Zabkar -- Please remove one 's' from my address when replying by email. |
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In article , Ross Herbert
writes: The device which looks like a "light bulb" might be a gas arrestor to limit lightning surges (by going low resistance) but these devices are not usual in most telephones. I'd say that's probably what it is, as it looks like one of those gass filled light bulbs. Wayne Sallee |
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wayne posted:
In article , Ross Herbert writes: The device which looks like a "light bulb" might be a gas arrestor to limit lightning surges (by going low resistance) but these devices are not usual in most telephones. I'd say that's probably what it is, as it looks like one of those gass filled light bulbs. Some 60's vintage phone circuits used an NE2 in the ringer. It modulated a high-piched oscillator to create a "tweet" effect. Also, you could observe the NE2 flashing through the phone's translucent case. Don |
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In article , Franc Zabkar
writes: Disable your phone's ringer circuit by desoldering one pin of the 1uF or 0.47uF 250VAC cap in that area. Call the phone using your mobile. You won't hear it ring, but if your phone stays alive, then the problem is somewhere in its ringer circuit, probably a "ring detect" IC. These ICs contain the bridge rectifier alluded to in my other post. Is that a foil cap or an electrolite cap? I found a large foil cap that reads: TK 1.0K 250V Wayne Sallee |
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