Tektronix O o c a o o, O o o O a a, Maintenance- 494A/494ApServtceVot.1 Diode Color Code

Maintenance- 494A/494ApServtceVot.1

Diode Color Code

The cathodeof each glass encaseddiode is indi- gated by a stripe, a series of stripes,or a dot. Some diodeshavea diodesymbolprintedon one side. Figure

6-2 illustratesdiode types Lnd potaritymarkings'that are usedin this instrument.

ct66.t-14

Figure6-2. Diode polartty marklngs.

Multiple Terminal (Harmonica) Connectors

Som€ int€rcircuitconnectionsare madethroughpin connectors that are mounted in a harmonicatype- holder. The terminalsin the holder, are identifiedty numbers that appear on the holder and the circuit diagrams. Connectorsare identifiedon the schematic and boardwith eitherthe prefixletterp or J followedby

acircuit number. Connectororientationto the circuit board ls keyedby a triangleon the holderand the cir_ cuit board(seeFigure6-3).

6-18

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(x)95-11

Flgure6-3. Multpln (harmonlca)conneciors.

Resistor Values

Many types of resistors(suchas composition,metal film, tapped,thick film resistornetworkpackage,plate, etc.) are used. The value is eithercolor coded in accor- dancewith the EIAcolor code, or printedon the bodyof the component.

Capacitor Marking

The capacitancevalue of ceramicdisc, plate, and slug, or small electrolyticcapacitors, is marked in microfaradson the side of the componentbody. The ceramictubularcapacitorsand feed-throughcapacitors are color coded in picofarads.

Soldering Techniques

Disconnectthe instrumentfrom its power source before replacingor solderingcom- ponents.

Extremecaution must be used when removingor replacingcomponentsbecausethe instrumentcontains severalmultilayercircuitboards. Excessheat from the

solderingiron and bent componentleads may pull the plating out of the hole. We suggest clippingthe old

componentfree. Leaveenoughlead lengthso the new componentleadscan be solderedin place.

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