Fuses and Conventional Resistor Removal/Replacement

1.Clip each fuse or resistor lead at top of circuit board hollow stake.

2.Securely crimp leads of replacement component around stake l/8 inch from top.

3.Solder the connections.

CAUTION: Maintain original spacing between the

replaced component and adjacent

components and the circuit board, to

prevent excessive component temperatures.

Circuit

Board

Foil Repair

 

 

 

 

 

 

 

 

Excessive

heat

applied

to

the

copper

foil

of any

printed

circuit

board

will weaker.

the

cdhesive

that

bonds

the foil to

the circuit board,

causing

the

foil

to separate

from,

or

“lift-off:’

the board.

The

following

guidelines

and

procedures

 

should

be followed whenever this condition is encountered.

 

 

In Critical Copper Pattern Areas

High component/copper pattern density and/or special

voltage/current characteristics make the spacing and integrity of copper pattern in some circuit board areas more critical than in others. The circuit foil in these areas is

designated as Critical Copper Pattern. Because Critical Copper Pattern requires special soldering techniques to ensure the maintenance of reliability and safety standards, contact your Hitachi personnel.

At IC Connections

To repair defective copper pattern at IC connections, use the following procedure to install a jumper wire on the copper pattern side of the circuit board. (Use this technique only on IC connections.)

1.Carefully remove the damaged copper pattern with a sharp knife. (Remove only as much copper as absolutely necessary.)

2.Carefully scratch away the solder resist and acrylic coating (if used) from the end of the remaining copper pattern.

BARE JUMPER

Install Jumper Wire and Solder

3.Bend a small “U” in one end of a small-gauge jumper wire and carefully crimp i! around the IC pin. Solder the IC connection.

4.Route the jumper wire along the path of the cut-away copper pattern and let it overlap the previously scraped end of the good copper pattern. Solder the overlapped area, and clip off any excess jumper wire.

At Other Connections

Use the following technique to repair defective copper

pattern at connections other than IC Pins. This technique involves the installation of a jumper wire on the component side of the circuit board.

DEfECTlVE

Insulated Jumper Wire

Remove the defective copper pattern with a sharp knife. Remove at least l/4 inch of copper, to ensure hazardous condition will not exist if the jumper wire opens.

Trace along the copper pattern from both wire sides of the pattern break and locate the nearest component directly connected to the affected copper pattern.

Connect insulated 20-gauge jumper wire from the nearest component on one side of the pattern break to the lead of the nearest component on the other side.

Carefully crimp and solder the connections.

CAUTION: Be sure the insulated jumper wire is

dressed so that it does not touch components or sharp edges.

Frequency Synthesis (FS) Tuning Systems

Always unplug the instrument AC power cord before

disconnecting or reconnecting FS tuning system cables and before removing or inserting FS tuning system modules.

The FS tuner must never be disconnected from the FS tuning control module while power is applied to the instrument.

When troubleshooting intermittent problems that might be caused by defective cable connection(s) to the FS tuning system, remove the instrument AC power as soon as the defective connector is found and finish confirming the bad connection with a continuity test. This procedure will reduce the probability of electrical overstress of the FS

system semi-conductor components.

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Hitachi 50SBX78B, 60SBX78B service manual Insulated Jumper Wire, Bare Jumper

60SBX78B, 50SBX78B specifications

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