Tektronix 494AP O o E a o o o c o o A o o a o a o o, Replacingassembliesand Subassemblies

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lf you desire to removethe componentl€ads, use a J.5Y ol tess pencil type iron. Straigtrten-theteads on me oacKsideof the board;thenwhenthe sotdermelts, gently puil the sotdered tead through the hote.

-remove A

desolderingtool should be used to the old solder. Use a desolderingtoot that has a low build-upof staticcharge,such as SiMerstatSoldapulltdesolder- ing tool, whenunsolderingintegratedcircuiisor transis_ tors.

Replacing the Square pin tor the

Multi-pin Connsctors

It is importantnot to damageor disturbthe ferrule when removingthe old stub of a broken pin. Tne ter_ rule is pressed into the circuit board and providesa basefor solderingthe pin connector.

lf the broken stub is long enough,grasp it with a pairof needlenose pliers,apptytreatlwiih a smallsold- ering iron, to the pin base of ine ferrute and pull the old pin.out. (Ihe pin is pressedinto th€ terruieso a firm pullis r€quiredto pultit out.)

lf the brokenstub.is-tooshort to graspwith pliers, use a smalldowel(0.029inchin diameter;clampedin a vise to.push the pin out of the ferruleafter the solder hasmelted.

The old ferrule can be cleanedby reheatingsocket and placinga sharpobjectsuchas a toothpicklr small dowel lnto the hote. A O.Oglinchdriil mountedin a pin vise may also be usedto reamthe solderout ol the old ferrule.

-Ur." a pair of diagonal cutters to removethe ferrule from the new pin; then insertthe pin intothe otd ferrule andsolderthe pin to both sidesoi the ferrute.

lf it-is,-necessary.to

.bend the new pin, grasp the base of the pin with needle_nosepliirs and bend againstthe pressureof ths pliErsto avoidbreakingthe boardaroundthe ferrule,

Servicing the VR Module

The VR modulerequiresmechanicatsupportwhen it is installedon board extenders. Mechanicalsupportis provided.by moving the mountingplate at the upper :'.qeof the modut€ (Figure 6_Anfti the bottom sicte. This allows installationof a mountingscrew througha supportbracketinto the mountingplatescrew hole as shown in Figure6-48. For bettei iupport, we recom- mend using a second bracket on the other end. Removethe bracket,turn it over and installit so the threadedstudsare belowthe module.

Maintenance- 494AJ494ApServiceVot.1

A. Locetionrnd positionof mountingplate.

VR mountingptate

B, VR module on €rtender boards and secrred for rervicing.

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Figure6.4. Serviclngthe VR ass€mbly_

REPLACINGASSEMBLIESAND

SUBASSEMBLIES

Most assembliesor sub-assembliesin this instru- ment are easily removedand replaced. The following describesproceduresfor replacingthose assemblies that requirespecial attention. Top and bottom views are shownin Figures6-5 and 6-6, respectively.These illustrationsshow the locationand identifymostassem- bliesbytheirnameand assemblynumber.

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