Replacing Components on the Circuit Boards

Fig. 4-19. Band A and B local oscillator assemblies.

3. When the lead comes out of the board it should leave

a clean hole. If not, the hole should be cleaned by reheating

It is best to remove the circuit board assembly to replace

the solder and placing a sharp object such as a wooden

components, because melted solder at the connections will

toothpick or enameled wire into the hole to remove the old

wick through the plated eyelets and can produce electrical

solder.

shorts. If the component is replaced without removing the

4. Clean the leads on the new component and bend them

board make certain an electrical short does not exist.

to the correct shape to fit into the holes. Insert the leads,

Use electronic grade 60/40 solder and a 15-watt pencil

making certain the component seats the same as the original,

soldering iron with a 1/8 inch or smaller, chisel tip. The

5. Apply the iron to the connection at the back of the

soldering iron tip should be clean and properly tinned for

board and apply only the amount of solder required to form

maximum heat transfer. Higher wattage irons may damage

a good electrical connection.

the bond between the etched wiring and the base material.

6. Check the front or component side of the board to

The following technique is suggested in the replacement

insure that the solder has filled the plated eyelet.

of a component on the circuit board assembly:

1. Remove the component by cutting the leads near the

NOTE

body. This frees the leads for individual unsoldering,

Some components can be damaged by heat. A

2. Grip the lead with needle-nose pliers. Apply the tip

hemostat or forceps, between the component and

of the soldering iron to the connection at the back of the

the connection will protect the component from

board, then pull gently to remove the lead.

excessive heat.

4-15