DEC DECtape 551 Manual page 64

Supply (blue terminal) is supplied to the modules; in the up position, the externally supplied
marginal-check voltage (yellow terminal) is applied to terminal C of the delay and pulse amp-
I
ifier modules only.
CAUTION
Make certain that all marginal check on/off switches on each rack
of logic.are off before performing the following procedure. Other-
wise, damage to individual logic modules may result.
To perform the checks:
1. Energize the marginal check supply and adjust the outputs to supply the nominal
+10 and -15 volt outputs.
2.
Start equipment operation in a repetitive program or in a routine which fully
utilizes the circuits in the rack to be tested.
3.
Set the top switch on the rack to be checked to the up position.
4. Lower the +lO-volt marginal-check power supply until normal system operation
is interrupted. Record the marginal-check voltage. At this point marginal transis-
tors can be located and replaced, if desired.
5. Start equipment operation. Then increase the +10-volt marginal-check supply
until normal operation is interrupted, at which point record the marginal-check
voltage. Transistors can again be located and replaced.
6. Reset the top switch to the down position.
7.
Repeat steps
2-6
using the center switch on the logic rack be ing checked.
8. Repeat steps 2-6 using the bottom switch on the logic rack being checked while
adjusting the -15-vdc marginal-check supply.
9. Reset the marginal-check power supply switch to the OFF position.
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