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A65, A75 & P75 Service Guide
Fault diagnostics
Fault Action
No power Check mains fuse
Check transformer connections
Check power supply rails
Stuck in protection Check power supply rails
Check protection circuit voltages
Check for dry joints on o/p devices
Intermittent audio on one channel Check for dry joints around o/p
devices
Fails to respond to commands Check supply to remote circuit
Check IC Z900
Check remote flex foil cable
Check for dry joints on selector pcb
Volume control rubs on front panel Pull knob out from fascia
Audio crackles on o/p Check for component break down
using hot air gun & freezer spray
Check transformer connections
Power supply test points
Position Voltage
LK125 +37 volts DC
LK126 -37 volts DC
LK271 or black speaker terminal 0 volts
LK303 +15 volts DC
LK301 - 15 volts DC
Q300 emitter +38 volts DC
Q304 emitter +38 volts DC
Q302 emitter -38 volts DC
Q305 emitter -38 volts DC
D910 emitter +5 volts DC remote supply
IQ settings
Model IQ setting Comments - (22/01/02)
A65 37mV
A75 37mV
P75 37mV
A85 12mV Set for 8.5mV cold, reset for 12mV when warm
P85 12mV Set for 8.5mV cold, reset for 12mV when warm
A65 plus 12 to 15mV
A75 plus 12 to 15mV
P75 plus 12 to 15mV
Hints & tips
!
To isolate a fault between pre and power stage remove C602 (left channel) or C702 (right
channel).
!
Always check and re-solder o/p device SAP15N and SAP15P pin connections.
!
Replace Z900 IC if software version is below version 3 ( note version 82 is also ok ).
!
Make sure R127 is not touching LK130.
!
When replacing the top cover with a new top it may be necessary to re-drill the fixing holes.