Heathkit SB-401 - TROUBLESHOOTING CHART

Page 118
Gg hearuxit
TROUBLESHOOTING CHART
TRANSMITTER
DIFFICULTY
POSSIBLE
CAUSE
Some or all of the tube
filaments fail to light,
TURN TRANSMITTER
OFF IMMEDIATELY,
No DC voltage at heterodyne
oscillator test socket, NOTE:
Applies only if SBA-401-1
Crystal Accessory kit is
installed,
No final plate current,
Full scale plate current
meter reading with
no signal input,
Relay does not close
when key is down
with Mode switch
in CW, and the
Function switch in
the TRAN or TRCV
position,
No carrier generator output,
NOTE: Applies only in CW or
TUNE modes unless SBA-401-1
Crystal Accessory kit is
installed,
Green power transformer lead not con-
nected,
Short or open in the filament circuit,
Fuse not installed or blown,
Pinched wires under chassis shields,
Check voltages and wiring of tube socket V8,
Check Band switch wiring,
See that crystals are in proper sockets, J
Poor or no ground connection at crystal
sockets,
Incorrect wiring of coils,
Regulator tube V7 (OA2) not functioning,
Function switch incorrectly wired,
Check voltages and wiring of tube sockets
V10 and Vil,
Check cathode metering circuit,
Check meter,
Check wiring of Bias Adjust control,
Check grid voltages of tube sockets V10 and
Vi1 (should be -50 V DC),
Check cathode metering circuit,
Check wiring of Bias Adjust control,
Check wiring of bias power supply.
Defective relay RL1 or RL2.
No B+ voltage present,
Check wiring and voltages of tube sockets
vi, V12, and V13.
Tone oscillator not working,
Anti-VOX control set too high,
Excessive hum on Anti-VOX line,
Phone patch jack shorted to power trans-
former case,
Low line voltage,
Diode D105 open,
See that crystals are properly installed,
Mode switch incorrectly wired,
Check voltages and wiring of tube sockets
V2 and V3,
Check wiring of relay RL1.
Bias voltage not removed from tube socket
V3.
Shorted coaxial cable to Mode _ switch,