Yaesu FT-901DM Maintenance Service Manual page 65

SERVICING
SOLDERING AND DESOLDERING TECHNIQUE
ON PRINTED CIRCUIT BOARDS
The FT-901 circuit boards are tough, but mishandl-
ing during soldering can cause circuit traces to
"lift." While this does no permanent damage to the
board, much servicing trouble can result, because
of the tendency for this lifted trace to break. A
few simple precautions will keep your circuit
boards in A-1 condition.
1. Use only a 12 to 30 watt chisel-tip soldering
iron, Yes, some "repairmen" have been
known to use small blowtorches on cards.
=)
Use only a soldering iron equipped with a
three-wire cord, with the tip grounded. Also
acceptable is a soldering iron isolated through
a transformer. An old soldering iron or gun
may have 117 volts on the tip, and will
certainly cause more damage than it repairs!
3. USE ONLY 60/40 ROSIN CORE SOLDER.
Acid core solder should be thrown away if
you find it in your radio shop!
4, Use a solder sucker and solder tape to ensure
a professional repair job.
§. If you do lift a trace, don't worry! Read on
to find out how to repair traces like a pro.
IMPORTANT
The circuit boards used in the FT-901 are not
keyed, and it is possible to install a board back-
wards, or to install it in the wrong socket.
If you have several boards out of the chassis at
any one time, be certain to install the boards cor-
rectly into their sockets. Use the reference plate
which is installed above the circuit board rack.
3-10
VR 1801
+ 6v Ser
—— RECT C UNIT PB-1717 +
+ +
(RECT A UNIT PB-1708
vr 203
+ + +
ALC METER SET GAIN LEVEL
NB RF PROCESSOR UNIT PB-1703
vR 202 VR203
=
+ FILTER UNIT PB-1716 +
vr 401 vr 402
+ S METER +
FULL SET ZERO SET
1F UNIT PB-1704
VR 501
APF SELECTIVITY
AF UNIT PB-1705
VR602 VR601 VR603 $601 TC 601
DELAY + vox + + 2 = _ marx|
3 + +
8 & + free
A-TRIP. sipeTone =
L— + VOX/ MARKER UNIT PB-1846 + ——
+ +
CARRIER FREQ CARRIER
FSK SHIFT CWAM. VR 701
UsB \s8
704 703 702 701 te 705
CARRIER UNIT PB-1706
LO4L-8d LINN
WS 108
NOUVIAaG
206 HA
AutgyaNrT
£06 UA
LOG uA