Teletype SA110 Checkout And Troubleshooting page 9

ISS 1, SECTION 578-200-300
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SAll0 PARITY FAILURE DETECTOR TROUBLESHOOTING CHART (continued)
NO. TROUBLE INDICATION
ANALYSIS AND RECOMMENDED ACTION
2.
c.
If
fuses are good, measure the voltage between posts 13 and 14
(cont)
on card MC405. If this voltage is less than +5.0 volts, measure
the voltage between posts 13 and 25 on card MC405. If this
voltage is less than +10 volts, remove fuse F2 and measure .it
again. If it rises to about +14 volts, the +6 or +14 volt
supply voltage is being loaded by card MC402-04 or card MC405.
Repair involves unsoldering leads and components to locate the
overload, so the entire SAll0 must be replaced.
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d.
If
the voltage between post~ 13 and 14 is less than +5.0 volts
and the voltage between posts 13 and 25 is less than +10 volts
but does not rise with fuse F2 removed, the transformer, diode
block, or electrolytic capacitor portion of the power supply is
defective (or line voltage is too low). Repair the power supply
or replace the entire SAll0.
e.
If the voltage between posts 13 and 14 is less than +5.0 volts
but the voltage between posts 13 and 25 is +10 volts or more
(about +14 volts), resistor R41 or zene;r diode ZDl (both on
card MC405) or power transistor Q14 (on heat sink) is defective.
Repair the power supply or replace card MC405 (TP322405) or Q14.
f. If the voltage between posts 13 and 14 is +5.0 volts or
more, turn PARITY CHECK switch to ON ;md request a long
message transmission from another station. Measure the
voltage between slip connector terminals 2 and 3 (EIA
input) or 2 and 1 (all other inputs) on card MC405 while
the message is being received. If the voltage between
terminals 2 and 3 or 2 and 1 is a steady positive voltage
(about +6 volts), check the contacts and wiring on the
PARITY CHECK switch (8566WD or 8567WD). Repair any faults
found.
g. If the voltage measured in step f fluctuates near 0 volt
(positive or negative), measure the voltage between slip
connector terminal 2 and post 18 on card MC405 while a
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message is being received. If this voltage is a steady 0
volt (approximately), the input amplifier (8538WD) is de-
fective. Repair it or replace card MC405 (TP322405).
h. If the voltage measured in step g fluctuates near +3 volts
(from 0 to +6 volts), measure the voltage between slip
connector terminal 2 and post 16 on card MC405 while a
message is being received. If this voltage is a steady
positive voltage (about +6 volts), card MC402-04 is
defective. Repair or replace card MC402-04 (TP322402-04).
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