Fuses and Conventional Resistor Removal/Replacement At Other Connections
1. Clip each fuse or resistor lead at top of circuit board Use the following technique to repair defective copper
hollow stake. pattern at connections other than IC Pins. This technique
involves the installation of a jumper wire on the component
2. Securely crimp leads of replacement component around side of the circuit board.
stake l/8 inch from top.
II II
3. Solder the connections.
CAUTION: Maintain original spacing between the
replaced component and adjacent
components and the circuit board, to
prevent excessive component
temperatures. DEFECTIVE
Circuit Board Foil Repair
Excessive heat applied to the copper foil of any printed
circuit board will weaken the adhesive 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 Insulated Jumper Wire
High component/copper pattern density and/or special
voltage/current characteristics make the spacing and 1. Remove the defective copper pattern with a sharp knife.
integrity of copper pattern in some circuit board areas more Remove at least 114 inch of copper, to ensure hazardous
critical than in others, The circuit foil in these areas is condition will not exist if the jumper wire opens.
designated as Critical Copper Pattern. Because Critical
Copper Pattern requires special soldering techniques to 2. Trace along the copper pattern from both wire sides of the
ensure the maintenance of reliability and safety standards, pattern break and locate the nearest component directly
contact your Hitachi personnel. connected to the affected copper pattern.
At iC Connections 3. Connect insulated 20-gauge jumper wire from the
To repair defective copper pattern at IC connections, use the nearest component on one side of the pattern break to
following procedure to install a jumper wire on the copper the lead of the nearest component on the other side.
pattern side of fhe circuit board. (Use this technique only on Carefully crimp and solder the connections.
IC connections.) CAUTION: Be sure the insulated jumper wire is
1. Carefully remove the damaged copper pattern with a dressed so that it does not touch
sharp knife. (Remove only as much copper as absolutely components or sharp edges.
necessary.)
Frequency Synthesis (FS) Tuning Systems
2. Carefully scratch away the solder resist and acrylic Always unplug the instrument AC power cord before
coating (if used) from the end of the remaining copper disconnecting or reconnecting FS tuning system cables
pattern. 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
Install Jumper Wire and Solder reduce the probability of electrical overstress of the FS
system semi-conductor components.
3. Bend a small ?U? in one end of a small-gauge jumper wire
and carefully crimp it 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.
8 |
ACEC
