HP 9020 Service Manual page 103

Assembly Access
4-3
Static damage is not always catastrophic. Sometimes a part slowly degrades, resulting in deteriorat-
ing performance. For example, internal resistance changes cause speed or voltage changes. Results
include intermittent or latchup problems (for example, a line printer prints bad data).
When disassembling the computer, a portable conductive field service antistatic kit should be used
to eliminate ESO when handling or temporarily setting aside ESO-sensitive parts. The kit contains a
wrist strap, antistatic mat, and ground cable.
Carefully observe the following procedures when disassembling the computer:
• Components, PC assemblies, finstrates, other assemblies and equipment should always be
stored, transported, and shipped in antistatic or conductive containers.
• ESO-sensitive items must never be handled by ungrounded personnel, nor should they ever
be stored on nonconductive surfaces or near nonconductive materials.
• Field support should keep all replacement PC assemblies and components in antistatic or
conductive bags. The customer engineer should be grounded when working on products. A
field service antistatic kit is available; it includes a static-free work station, ground cords, wrist
straps, and board storage space. The failed board should be placed in a static-free bag for
return to manufacturing site.
• Removal of ESO-sensitive devices from an assembly must be done at a static-safe work station
using all precautions. Suspect or rejected components, PC boards, and subassemblies are to
be treated with the same care as good devices. Otherwise, further damage may result which
prevents tracing the cause of the original failure.
Before removing devices from protective container:
a. Clear work area of static hazards such as plastic cups, bags, envelopes, and papers.
b. Connect wrist strap.
c. Neutralize charges of ESO protective packaging containing an ESO-sensitive item and of
tools by placing the packaged item on an ESO-grounded work bench surface to remove
any charge prior to opening the packaging material. Alternately, charges can be re-
moved by grounded personnel touching the package.
d. Ensure that the computer is properly grounded before inserting ESO-sensitive items.
e. Remove ESO-sensitive item from ESO protective packaging using finger or metal grasp-
ing tool only after grounding, and then place on the ESO-grounded work bench surface.
• Place PC boards, finstrates, and components on table mat when not in static-shielding bags or
other protective containers.
• Clothing must never contact ESO-sensitive parts. Wrist strap does not bleed off charges from
clothing.
• Personnel handling ESO-sensitive items should avoid physical activities which are static pro-
ducing in the vicinity of those items. Such activities include wiping feet and removing or putting
on jackets or sweaters.
• Where ground straps cannot be used, personnel should ground themselves prior to removing
ESO-sensitive items from their protective packaging.
• Tools and test equipment used in ESO-protective areas should be properly grounded; hand
tools should not contain insulation on the handles or, if used, tools with insulated handles
should be treated with a topical antistat.