Adjustment Procedures - Onkyo A-809 Service Manual

A-809
ADJUSTMENT PROCEDURES
Adjustments and Checking the Protection Circuitry
1. Preparations
1) Place the unit on the workbench. (There should be about 15 mm of space between the base plate of the unit and
the work surface.)
2) Set up the unit as follows.
(1) No load
(2) No signal
(3) Volume turned all the way down
(4) Speaker switch OFF
(5) Power switch OFF
Note) Check the following points before making adjustments
(1) The power switch should be OFF.
(2) The interior of the unit should not be warm.
2. Idling current adjustment
1) Turn the power switch ON and allow the unit to warm up for about 10 minutes.
(1) Adjust R535 (R536) so that the voltage at test point VCT-IID on the NAAF-4209 circuit board is 15mV+5mV.
Note) Semi-fixed resistors enclosed in parentheses (_ ) are for the right channel.
3. Check of operation of protection circuitry
1) Check of operation of protection relay
(1) Confirm that the relay turns ON approximately 5 seconds after the power switch is turned ON.
(2) The SERVO indicator LED should light at the same time.
(3) The relay should turn OFF approximately 0.5 seconds after the power switch is turned OFF.
2) Check of DC detection and servo circuitry operation
(1) Turn the power on with no load.
(2) After the speaker relay turns ON, apply DC + 200mV to the CD input terminals. Confirm that the relay turns OFF.
(3) Confirm that operation is the same as (2) above when an input of DC—200mV is applied.
Note) Under no circumstances connect a load or short the speaker terminals when performing the above test.
3) Signal input from the circuit illustrated below with no load.
(1) Confirm that the speaker relay does not turn OFF even when a 2 ohm load is connected when a peak value of 30VP
is output.
(2) Next, confirm that when a 1 ohm load is connected the speaker relay switchse OFF and ON a couple of times
and then stays OFF.
Note) The period before that relay stays OFF should not last for more than 1 minute.
Relay OFF status can be canceled by switching the power OFF.
Low-frequency
oscillator Anplifier
SP Load
Differe- Attenua~ | CD IN OUT resistance
ntiator tor |
Square wave The unit's volume
SOHz, 10V p-p contro! may also
be used. Oscillo-
scope
3.3 KQ Ol
uF
3.3 KQ
OUTPUT
°
o—w—
Square wave input from
low-frequency oscillator
10 KQ
ue
50 Hz, 10V p-p Tp
40