Myron L 729II - Manual (Page 21)

3. CHANGING ANALOG METER SCALE (DIAL)
After changing configurations (pH to ORP or visa versa) on an
analog model 720II it will be necessary to change the meter scale
(dial). The following steps will guide you through the change.
Please read caution carefully.
Exercise extreme caution while working on meter.
Meter movement, and/or pointer (needle) may be
damaged beyond repair. It is recommended only
qualified personnel change scales.
DO NOT allow dust to enter the case while it is open.
Failure to follow these instructions may cause
irreparable damage, and will VOID the warranty.
Briefly -
The meter is removed from front panel (except OEM models).
The cover is removed.
The hex screws retaining the scale are removed, and scale
is slid out the top.
New scale is slid in place, and screws reinstalled.
Cover aligned, installed and zero set.
Physical
For OEM models skip to #4.
1. Using a wrench, nut driver or pliers remove the two (2)
large nuts retaining the circuit board wiring harness
connectors. Red wire is PLUS (+),
Brown wire is MINUS (-). See figure II.G.2.
2. Using a standard slot screwdriver remove the four (4)
screws, and the backing plate holding the meter to the
front panel as shown in figure II.G.2.
3. Remove meter. Do not lose the gasket between the
meter and the front panel, it must be reinstalled upon
reassembly. See figure II.G.3. Align gasket to front
panel so as the gasket does not show when meter is
assembled to front panel.
4. Using a wide blade standard slot screwdriver, starting at
a bottom corner, CAREFULLY pry the clear plastic cover
loose from the movement case. See figure II.G.4.
5. Using a 1/8” (3.2mm) hex driver, remove the two (2) small
screws holding the scale (dial). See figure II.G.5.
6. To remove the scale, lightly press on bottom of scale,
the top will lift up. Be extremely careful not to bend the
pointer (needle) or to move the Zero Adjust (ZA).
See figure II.G.5.
7. Grasp top and slide scale slowly out from top. Be
extremely careful not to bend the pointer (needle) or to
move the Zero Adjust (ZA). See figure II.G.5.
17
CLEAR COVER
Pry Here Carefully
CASE
Figure II.G.4
Figure II.G.5
Grasp Scale Here
and Slide Out TOP
SCALE (dial)
Pointer (needle)
Inverted "Y"
1/8" (3.18mm)
Hex Screws (2)
METER CASE
Press
Lightly
Here
0
!
CAUTION - READ FOLLOWING CAREFULLY
GASKET
Figure II.G.3
Figure II.G.2 Harness to Main
CB Connector
+
Backing Plate
METER
Mounting Screws (4)
BROWN WIRE RED WIRE