Troubleshooting
System Halting and Voltage Measurements (#73)
Summary: Voltage reading on flat-cable buses can be performed using the #73 diagnostic or the diag-
nostic disk program, which is simpler and does not require access to the MIO. Either method
requires halting the system, during which time no calls can be made or features accessed.
However, this test will not disturb calls in progress. These measurements are important trou-
bleshooting aids when the TCIV is operating intermittently or is unable to access certain
physical numbers.
Step 1.
Step 2.
Step 3.
Step 4.
Step 5.
Dial #73 and enter the physical number of the line to be tested, then ground pin 66 of the
A
connector
on the back of the MI0 (refer to Drawing KC1461). This ground halts the system
and produces a static condition on the flat-cable buses.
Using a one-megohm (or higher) digital meter, measure the voltages on the flat-cable pins.
For TC4150 LLM’s, access may be gained at the end of the flat-cable. For TC4110 SC25’s or
TC4120 SCC25’s, access may be gained by unplugging the flat-cable from any board not
under test. For ease of testing, a flat cable connector (e.g.: 3M NO3399) can be crimped to the
flat-cable to provide test access.
Refer to the MI0 schematic (KC1461) to identify each pin/conductor number and verify the
voltage reading obtained represents the appropriate binary number.
If Physical Line 7 were entered in the display, the binary number 7 (0000000111) may be
verified by measuring 12
volts
on LLM flat-cable conductors 18, 20, and 2 1 and 0 volts on
conductors 12,
13,
14, 15, 16, 17, and 19. The least significant four bits, measured on con-
ductors 19, 20, 18, 21 (Pin 18 is at binary position 2), represent the LLM circuit number (0 to
15). The remaining bits represent the DIP switch setting of the LLM.
For speakers, the flat cable is divided into two sections. Section one is a five-bit relay select
number (0 to 24), respectively representing relays 1 through 25. Section two is a six-bit binary
module select number which represents the DIP switch setting for the module under test.
Using a one-megohm (or higher) digital meter, measure the multiplex
(MPX)
voltage
from
the TC4150 LLM to verify the following for the specified line. This will require taking the
phone on and off-hook at the remote station associated with the physical number under test:
On-hook Less than
5
volts
Off-hook Greater than 7 volts
Open circuit
6 volts (+/- 0.5 volts)
Note: An
open circuit condition may indicate that there is no LLM or no line-hybrid for the
specified circuit. If the open circuit voltage is outside the range shown, an LLM is loading the
MPX line and needs to be repaired or replaced.
Using a one-megohm (or higher) digital meter, measure the voltage between wires
A and B
on
the
SC25 bus
and verify the following by using the call-in switches at the target remote
location associated with the physical number under test:
No Call-in Less than 100 mvolts
Normal Call-in Over 600 mvolts
Emergency Call-in 200 mvolts
(Note: This is from a switch with a resistor.)
Note:
Use appropriate troubleshooting techniques and schematics to progressively define any
problems in individual expansion modules, circuits, and components.
Step 6. Remove the jumper from pin A:66.
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1989 Rauland-Borg Corporation (Orig. 10/88; Rev. l/89)
