Table of Contents
Advertisement
2 .. 32. 2 HAMMER CHECK
This check occurs if the harrrrer drivers and
ccmpare circuitry do not operate properly ..
Each of the conditions detected sets the
hamner check latch..
In addition, unique
combinations of check bits (C1, c2. and C3)
are set tc indicate which error causes the
hammer check..
The check planes can be
analyzed to help correct the errcr-causing
ccnditicn..
Listed here are the error
conditions detected and the check flanes
that are set.
Hammer driver on but no
COmfare-- PIC, C2
Compare but harrmer driver did
not turn on--PIC, C1, C2
Compare with FIC already
on--PLC. C1, C2, C3
Hammer driver on with PLC
already on--PLC, C2, C3
No compare at last scan--PLC, C3
Any d:.her comtinations of PLC with C1, C2,
or C3 indicate failures in the check
circuitry..
The FIC tit alone indicates
proper operation.
2.32.3 CCIL-PROTECT CHECK
This check occurs when a conditicn cccurs
that may cause damage to hammer coils and
drivers..
The +60V return tc the harmer
ccils is cpened ty turning off the 60V
control contactor.
This contactor is
controlled by a reed relay..
If nc check
exists, the reed relay is picked and the
+60V control is present.
A coil-protect check can cccur f cr 3
reasons.
1.
The hammer check circuitry detects that
a harrrrer driver is on tut shculd net
be.
This is detected for each hammer
driver when printing is taking i;lace.
2..
A Sfecial current sense reed relay
assembly detects that +60V central
airrent of at least 3 amps is being
drawn by the harrrrer coils at a tirre
when no hammer drivers should be on.
This detects any harrrrer ccil current
that cccurs when no printing is taking
place.
3.
The special current sense reed relay
asserrtly is checked during printing to
see if the reed relay picks if a harrrrer
driver is on.
This ensures that the
check as stated in iterr 2 is cferative.
The check in item 1 can be blocked by
ci;erating the coil protect check byi;ass
switch S3.
This switch tlocks setting the
coil-protect check latch due to a banner
check..
This switch should te used only if
it has been determined that a false errcr
is causing the check.
Eliminating this
check may delay detecting a ccil-frctect
check until printing is complete.
This
switch causes the printer attention light
on the console to light.
All of the
preceding checks can be prevented from
dropping the +60V central by operation of
the current-limit switch S4.
This switch
opens a short circuit acrcss a 100-ohm
resistor in the +60V line to the hammer
coil returns.
With this resistor in the
circuit, a maxinun of 600rrA can be drawn
through any one circuit.
This limited
current prevents damage tc haromer coils and
drivers even if they are on all of the
time.
A relay cperated by the switch
tlocks the coil-protect check from dropping
the +60V control.
2.32 .. 3.1 Hammer Driver coil--Fuses
There are four 6-amp fuses in the 2025:
F30, F31, F32 and F33.
Their purpose is to
protect the banner coil return wiring in
the 1403 and the 1403 signal cables.
Under
certain power-down conditions, these fuses
may l:low l:ecause all of the hammer drivers
may be on for up to 50 milliseconds..
The
poY4er-down condition that rr.ay cause this
~rotlem
is the loss of one of the logic
voltages that control the addressing matrix
to the hammer drivers.
Another condition
that may blow one or rrore cf the fuses is a
short on one of the hammer coil return
lines in the 1403.
After the fuse has blown, coil protect
checks occur.
Print ready is off, print
check is on, and the chain motor is not
running because +60V CTR1 is turned off.
If this condition occurs only when printing
is attempted, the S3 switches should l:e
turned on.
If the coil protect check no
longer occurs, cne or more of the fuses is
prol:al:ly tlown.
The power-check light is also turned on
if any fuse (F30 through F35) is open.
A
power-down condition does net occur.
The
light is turned off when the open fuses are
Leplaced.
Because these fuses have ceramic
cases, it is necessary to check them with a
meter or test light.
2.32.4 SYNC CHECK
This check occurs when the PCC counter gets
out of step with the chain or train.
This
is detected at horre gate tine, which is
generated l:y an extra drun FUlse from the
chain or train, and indicates that the PCC
should contain a count cf hex 01 (non-MCS).
A resync circuit is used to resync the
PCC automatically at MCS Home, except if a
sync check could cause an iwproperly
printed line.
A reset is given to the
printer-in-sync latch just before the
home-gate tirr.e, unless a blcck-reset latch
is on.
The l:lock-reset latch is set when a
2025
FE~M
(7/69)
2-17
Advertisement
Table of Contents
