Model 242L Operations Manual
Eberle Design Inc.
Page 4
a. Input voltage or pulse width does not meet the requirements of section 1.7.4 or 1.7.5.
Verify that the DC input voltage level is less than the DC Inputs True specification. Verify that
the DC input pulse width is greater than the Input Pulse Width Accept specification.
1.6.2 TROUBLE SHOOTING SEQUENCE
Apply 24 Vdc nominal power to DC POWER pin J1-B referenced to LOGIC GROUND pin J1-A. Connect
a jumper circuit to the DC inputs J1-D (J1-J) and J1-E (J1-K) to simulate the closure of the input
contacts. The following signal measurements are referenced to test point CH1 (CH2).
NOTE: internal test point “GND” is isolated from Logic Ground. Care should be exercised in probing
internal test points.
a. Input Bias Power Supply VCC
Voltage at test point VCC should be 19
1 Vdc with respect to GND.
Possible component faults are: controller U18, CR12, R14, transformer T1, CR30, reference
U25, or opto-coupler U21.
b. Regulated Power Supply VDD
Voltage at test point VDD should be 5
0.2 Vdc with respect to GND.
Possible component faults are: voltage regulator U26, inductor L2, diode CR29.
c. Microcontroller
Possible components at fault are: microcontroller U20.
d. Output Circuit
Output signals are processed by the microcontroller U20 and appear at U20.10 (U20.9) and on
the display LEDs but are not appearing at the output pins.
Possible components at fault are: opto-coupler U8 (U9), output transistor Q7 (Q8).
1.7 SPECIFICATIONS
1.7.1 CONSTRUCTION
Printed circuit boards are double sided copper with plated through holes. Circuit boards are coated for
environmental protection.
1.7.2 MECHANICAL
Height .............................................................................................................................. 4.50 inches
Width ................................................................................................................................ 1.2 inches
Depth (excluding handle) ............................................................................................... 6.875 inches
1.7.3 ENVIRONMENTAL
Storage Temperature Range ....................................................................................... -45 to +85
o
C
Operating Temperature Range .................................................................................... -34 to +74
o
C
Humidity Range (non-condensing) ........................................................................ 0 to 95% Relative
1.7.4 ELECTRICAL
DC Supply Voltage Minimum ............................................................................................... 10.8 Vdc
DC Supply Voltage Maximum .............................................................................................. 28.0 Vdc
DC Supply Power Maximum ............................................................................................... 2.0 Watts
DC Inputs
True (low) .............................................................................................................less than 8 Vdc
