Model LT3 cat 63348
serial no 2308429
Line Earth Tester LT3 Made by Evershed and Vignoles.
This was purchased at auction for £10 and it came with a case but
without any leads or instructions. I had no plug suitable for the
Bulgin 3 pin socket so dismantled the instrument to ascertain the
correct connections from the wiring within (red black and green) and by
making direct connections to a 13A plug was able to check that it
worked on my house wiring. I have indicated the pin connections on the
image below as it seems these come up for sale without the appropriate
leads. I have now replaced the socket with an IEC 3pin 5A one which
mates with a cable from a long gone computer. The opening in the
leather case is large enough to accommodate this without any
modification.
Please be aware that this
tester applies a large current through the
line and earth conductors without a corresponding current through the
neutral so any residual current device (RCD) in the circuit will trip.
The instrument is housed in the same pplastic mulding as the BM
series of Battery Meggers and incorporates the same two coil meter
movement, see here: Megger BM6 The
compartment at the rear being used to house two power resistors rather
than a battery.
End view showing connections to
Bulgin 3pin socket and rear compartment housing fuse and
resistors.
View of interior (a second printed circuit board hidden behind scale plate)
The top board which has the two neon
indicators includes circuitry to provide a DC voltage to power the
electronics on the main board shown below.
View of underside main printed circuit board
How old is it? I guess this one
was
made in early 1980 judging by the date code on the power resistors
though I believe the Lt3 was first made in about 1974. A later Mk 2
version was also produced.
What is it worth? Maybe £10-£20
