Simpson 2 Series - Page 31

Maintenance
OBSERVE POLARITY
When cells are replaced, be sure to observe the polarity of
the battery circuit. The cells are each held in place with
specially designed spring clips which also act as battery
contacts. Battery polarity is shown on the panel.
SUB-PANEL PARTS PLACEMENT
Beneath each resistor on the printed circuit is its part
number, as it is shown on the schematic diagram and in
the parts list. This mark will eliminate any doubt which
may arise as to the location of any of the resistors.
RECTIFIER REPLACEMENT AND RECALIBRATION
There are two small rectifiers which are located at the top
of the printed circuit, near the large 1.5 volt cell. These
are used to rectify the A.C. voltages for measurement.
They are shown as D-1 and D-2 in the overall schematic
diagram, Fig. 2.
Both rectifiers act in the meter circuit to effectively create
a full wave rectifying action. If either or both should fail,
the meter will show incorrect indications.
In case of rectifier failure, order a new rectifier from a
Simpson Parts Depot (pages 37-39), specifying the part
number as shown in the parts list. In order to maintain the
accuracy of the Model 270 Series 2, it is essential to replace
rectifiers with the type furnished in the original unit.
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