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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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5th Dec 2009, 12:58 pm | #41 |
Octode
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Location: Bath, Somerset, UK.
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Re: GPO 706 in trouble.
OK:
Correct. But do remove the regulator (that little slide-in, reversible PCB) and check for an eventual open-circuit between terms: T10 and T2. I say 'eventual', because your meter, set to 'Ohms', will charge up capacitor C3 (0.9uF). If you do measure a finite, steady resistance here, it's the capacitor at fault and it must be replaced. There is an open circuit (1 on my ohm meter) between T10 and T2 with the removeable card in or out or upside-down. Now I'm hoping this will give me the naughty component to replace....?? SEAN
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5th Dec 2009, 1:15 pm | #42 |
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Re: GPO 706 in trouble.
Please conform that '1' on your meter does indicate an open circuit. If it does, then with no test leads connected and the meter on ohms range a '1' will be displayed.
The use of terms such as no reading and zero reading is confusing, Better to talk of open circuit (infinite resistance) and short circuit (zero resistance).
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5th Dec 2009, 1:23 pm | #43 |
Octode
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Re: GPO 706 in trouble.
On Ohms - it reads 1 when the probes are not touching - so that is open circuit.
My meter is dodgy, but I think that is correct. SEAN
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5th Dec 2009, 1:26 pm | #44 |
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Re: GPO 706 in trouble.
Did the reading start low and then rise before settling at open circuit? This would indicate that the capacitor is being correctly charged.
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5th Dec 2009, 1:30 pm | #45 |
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Re: GPO 706 in trouble.
This thread is so long that I've lost touch with what the original problem was and what progress has been made. Does the bell ring on incoming calls?
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5th Dec 2009, 1:33 pm | #46 |
Octode
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Re: GPO 706 in trouble.
No, it was straight to open circuit.
SEAN
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5th Dec 2009, 1:56 pm | #47 |
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Re: GPO 706 in trouble.
In that case C3 is faulty. Check for cracks in the tracks leading to it.
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5th Dec 2009, 2:04 pm | #48 |
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Re: GPO 706 in trouble.
I should have said C1B is faulty. This is a 706, not a 746.
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