Troubleshooting Gm Detectors - LUDLUM MODEL 3 Technical Manual

Model 3
Ludlum Measurements, Inc.
Technical Manual
SYMPTOM
meter goes full scale
or "pegs out"
(continued)
no response to
radiation
no audio

Troubleshooting GM Detectors

1. If the tube has a thin mica window, check for window breakage.
If damage is evident, the tube must be replaced.
2. Check the
Vdc, or 460-550 Vdc for "peanut" tubes (Ludlum Model 133
series).
POSSIBLE SOLUTION
3. Remove the can and check for loose
or broken wires.
4. Ensure that the instrument's "can"
is properly attached. When attached
properly, the speaker will be located
on the left side of the instrument. If
the can is on backwards, interfer-
ence between the speaker and the
input preamplifier may cause noise.
1. Substitute a "known good" detector
and/or cable.
2. Has the correct operating voltage
been set? Refer to the calibration
certificate or detector instruction
manual
voltage. If the instrument uses
multiple detectors, confirm that the
high voltage is matched to the
current detector being used.
1. Ensure that the
is in the
2. Remove the instrument housing and
check the connection between the
circuit board and the speaker. Plug
in the 2-pin connector if necessary.
. For most GM tubes, the voltage is normally 900
HV
Page 7-3
Section 7
for correct operating
-
AUD ON OFF
position.
ON
April 2016
switch