Tektronix 494AP service manual @o @@tr, UpJ

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7. Reinstallp361.mountingbracketthen ptugpg045 ontoth€ powersupplyboardanOrepacJ the cover.

8. Set the instrumentwith the RF deck on the near side.then hold the power supply moduleat the rear of the instrumentso the rightsideis touctringthe side_rait andthe teft side is aboui1.5inchaboveiti side-rait.

9.Align connectorsp5041 and p1034 with their respectiveMother board and Interfaceboard connec- tors'thenpress the modureintopracebeh^/eenthe side rails.

10.Replacethe four moduleholdingscrews and the thre€flangescrews.

11.Reconnectthe.coaxialcablesand GplB cable,if appropriate,theninstallthecableclamp.

12.Replacethe instrumentcover.

High Vottage power Suppty

Ascrew must be removedbeforethe HighVoltage Power luqpty circuit board can Oe unpluggedand removed. The screw goes througt tt" iib"-rail into a nylon standoff bushing at the bottom corner of the board.

Removing and Replacingthe lst LO

. 1. Unplug and removethe multipinconnectorsto the assembty. Cut the tie_downthai hoids the black encasedRF coil to the semi-rigidcable.

.. 2. Using a S/16 inch open-endwrench,toosenand disconnectthe semi-rigidcoaxialcable.

3.Loosen and removethe four mountingscrews thatholethe assemblyto theRF deck. Removethe 1st LOassembly.

4.To replacethe assembly,reversethe removal procedure.Use a tie_downto ri-tie the RF coil to the semi-rigidcableto preventvibrationfrom breakingthe coifleads.

Replacingthe 1st LO Interface Board

The 1st LO assemblyincludesan interfacecircuit boardthat^c1nbe reptaced.To replacethe boardrefer to Figure6-7 and the following procedure. Use a desolderingtool to removetne sotOlras the teadsare unsoldered.

1.Unsolderand tiftone_endof C1014(g20uFcapa_ citor)at the top of the board

2.Unsolderandtiftoneendof VRl010.

3.Unsolderandliftthe+ leadof C1016.

4.Unsolderthe eightleadsto the oscillatorand lift the boardoff the assembly.

Malnfenance- 4g4Ll4g4ApServiceVot.1

A. Oscillator assembly.

Unsolder circled connections.

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B. Interface board showing terminals to unsolder for removal.

Figure6-7. Removingthe lst LO Intertaceboard.

Fan Assembly Removal

1.Removepowersupplyas describedin this sec_

tion.

2.Removesix screws that hold the power supply cover in place. Takethe coaxialcableout of the plastic retainerclip and lift the power supplycoverwithfan up, so harmonicaconnector pgO4Scan be disconnected and the coverremoved.

3.Removethe nuts and lockwashersthat hold the fan bracketsfrom the back side of the power supply housing.Thefan will fall free from the brackets.

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