Teletype SA110 Checkout And Troubleshooting page 6

SECTION 578-200-300
and remains on after test is complete until lamp housing
is depressed (blinks may be seen while the counter is
counting).
C. Significant Distortion Detection
2.18 Operation of the significant distortion check, if
used, may be checked with a TSG800 test set or
high speed 911 test set, if one is available. Introduce a
correct-parity signal containing about 40 to 45 percent bias
distortion, either marking or spacing, and check operation of
the receiver. The test signal should be punched correctly by
the receiver. Increase the distortion further and repeat. At
some point between 45 and 51 percent distortion, the
receiver should begin to punch incorrect characters and the
SAll0 should indicate continuous errors.
Note: The distortion percentages given above apply to
local testing only. If testing is done remotely, the
distortion introduced by the transmission lines must be
taken into account.
2.19 If the SAll0 garbles characters with less than 45
percent distortion or indicates errors for such
characters, or if it fails to garble characters distorted more
than 51 percent or indicate errors for them, refer to Part 3.
3. TROUBLESHOOTING PROCEDURE
GENERAL
3.01 Tools required for troubleshooting are listed in
Section 570-005-800. A volt-ohm-milliammeter is
also required.
3.02 Special terms used in troubleshooting are defined
as follows:
(a) Open circuit - no current fl(?wing
(b) Closed circuit - current able to flow
(c) Running open - open circuit condition at printer
or punch; shafts turn continuously and mech-
an.isms operate, but clutches do not latch, or punch
punches continuous NULL characters
(d) Running closed - closed circuit condition at
printer or punch; clutches latched and shafts do
not turn
(e) Garble incorrect characters printed or punched
3.03 Receiving troubles at the set can be caused by
malfunction of one or more of several elements.
The sender might garble or distort its signal; its data set might
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do likewise; the transrmss1on line might open or become
noisy; the terminal data set might open or garble signals; the
SAll0 might fail in a number of ways; or the terminal itself
might malfunction. The first step in troubleshooting is to
isolate the trouble to one or more of these sources.
3.04 To determine if the source of trouble is in the
terminal or ahead of it (SAll0 parity failure
detector, data set, etc), place the terminal in the local mode,
if possible, and check its operation. Abnormal operation
indicates that the trouble is in the terminal.
3.05 Troubles isolated to the terminal are not covered in
this section.
3.06 If terminal operation is normal in the local mode,
turn the PARITY CHECK switch on the bypass
switch or indicator assembly (if present) to OFF. (If the
SAll0 has no bypass switch or indicator assembly, discon-
nect it from line and place a wire strap between the data
input and the data output. Be sure to remove the strap before
reconnecting the ·sAllO to the line when this check is
completed.) Request a message transmission from a terminal
whose transmission the receiver could not copy correctly.
Abnormal operation indicates that the trouble is in the
sender or its data set, the transmission line, or the receiver
data set, provided that the SAll0 was installed correctly.
Verify
all
SAll0 connections if in doubt.
3.07 Troubles isolated to sending terminals, data sets, or
the transmission line are not covered in this
section.
3.08 If terminal operation is normal in the local mode
and in the line mode with th~ SAllO PARITY
CHECK switch OFF (or equivalent), but is abnormal with the
PARITY CHECK switch ON, the trouble is in the SAllO.
3.09 Trouble~ isolated to the SAllO parity failure
detector are corrected by replacement of a fuse or
card. Do not remove or insert cards with the power on.
Unplug the SAll0 first.
CAUTION: THE INTEGRATED CIRCUITS USED
ON THE SAll0 CIRCUIT CARDS ARE FRAGILE. 00
NOT DROP OR JAR ANY CARD OR ALLOW ONE
TO COME IN CONT ACT WITH SOLDER OR LOOSE
METAL PARTICLES.
3.10 Because of the complexity of the SAll0 circuits, it
is not practical to make some repairs to cards at
the terminal location. Damaged cards which cannot be
repaired quickly should be returned to a central facility for
repair.