Validation Test - DEC DECtape 551 Manual

receive logic level signals by eyelets provided on the power cable. Type 911 Patch Cords are
used to make these connections between eyelets on the plug. In this manner, logic operations
and voltage measurements can be made throughout the circuit. When using the Type 765 Bench
Power Supply, marginal checks of an individual module can also be performed.
Repair
In all soldering and unsoldering operations performed in the repair or replacement of components,
avoid placement of excessive solder or flux on adjacent components or service lines. When -'
solder ing semiconductor devices (transistors, crysta I diodes, and meta II ic rectifiers) wh ich may
be damaged by heat, the following special precautions should be taken:
1. Use a heat sink, such as a pair of needle-nose pi iers, to grip the lead between the
devic:e and the connection be ing soldered.
2. Use a 6-volt soldering iron with an isolation transformer. Use the smallest solder-
ing iron adequate for the work.
3. Perform the soldering operation in the shortest possible time to prevent damage to
the component and delamination of the module etched wiring.
When any component of the equ ipment is removed for repa ir or replacement, make certa in that
all leads or wires which are unsoldered or otherwise disconnected are legibly tagged or marked
for identification with their respective terminals. Replace defective components with those of
equal or greater quality and equal or narrower tolerance.
Validation Test
Following the replacement of any electrical component of the DECtape control, a test should
be performed to assure the correction of the fault condition and to make any readjustments of
timing or signal levels affected by the replacement. This test should be taken from the preven-
tive maintenance procedure most applicable to the portion of the system in which the error was
found. For example, if a filter capacitor was replaced in one of the power supplies, the rip-
ple check for that power supply should be repeated as specified under Power Supply Checks.
Or, if the Type 4401 Variable Clock is replaced, the associated test procedure for this module
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