Message 29866 in TECH.WW
From: G8MNY
Date: Sat, 12 Sep 26 08:41:00 Z
Newsgroups: TECH.WW
Subject: Wiring & Form Tapping out
Message-ID: <4892_GB7CIP>
Path: N2MH4|VE3KPG|GB7CIP
R:260912/0844Z 37079@N2MH4.#SENC.NC.USA.NOAM LinBPQ6.0.24
R:260912/0843Z 766@VE3KPG.#ECON.ON.CAN.NOAM BPQ6.0.25
R:260912/0841Z @:GB7CIP.#32.GBR.EURO #:4892 [Caterham Surrey GBR] $:4892_GB7CIP
From: G8MNY@GB7CIP.#32.GBR.EURO
To : TECH@WW
By G8MNY (New Aug 07)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)
Here is some basic methods of tapping out/fault finding wires in large
multicore cables or forms (car looms?).
DC BUZZER
If full DC access is easily available then a simple DC buzzer test will do OK.
Large cable
via earth/sheath/spare wire.
For in between connectors a Pin can be inserted into single wires to make
connection to confirm the identity or prove the fault, but doing so will damage
the insulation!
UNBALANCED AC TESTING
When no access to the wire is possible then AC testing can be done with a large
AF signal and sensitive AF Amp and headphones as the phone engineers use..
Large Cable
/// ///
Here the cable is not in audio pairs, the return path is via earth. The probe
is just an unscreened wire/rod connected to a short screened lead to the Amp.
The Amp is very high gain (10,000x e.g. a 741) & tailored for 1kHz.
The osc can be a steady tone or a pulsed tone, 3V AC is a good level to use.
When you hear the loudest tone in the detecting headphone from the cable, earth
that lead, and if the tone then goes, the send headphone gets louder, if not it
is just a loud crosstalk keep searching.
BALANCED TESTING
Large Cable
Here the cable is in audio pairs. When you hear the loudest tone in the
detecting headphone from the cable, short that pair of wires together, and if
the tone then goes, the send headphone gets louder, if not it is just a loud
crosstalk pair (fault?) keep searching.
Why don't you write an interesting bul?
73 De John, G8MNY @ GB7CIP
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