akira HTS-797AS, Service Manual

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Model No.: HTS-797AS
Version: 1.0
Cannot turn on
Strictly speaking, there are two types for the problems that this unit cannot be turned on. One is this
unit has no any reaction when you press STANDBY after the main power supply is on. The other is
there is display but no output and the relay cannot clutch when you press STANDBY after the main
power supply is on. Because the former type is similar with NO DISPLAY problem so please refer to
the checking way for that. Here we put emphasis on discussing the latter.
Phenomenon:
Turn on the main power and the power display light works normally. Press the STANDBY and this
unit displays normally but the sound of the relay’s clutching cannot be heard and thers is no output
either.
Analysis:
Because this unit only has one main transformer to supply the power so after it is turned on, the power
which display part and CPU’s work need has been added. That is the display has no realation with the
circuit of the main power relay. What is affected is the amplifier’s power supply is lacking so there is
no output or the output is very small.
Trouble shooting way and steps:
NO
YES
YES
YES
YES
NO
NO
NO
NO
Whether Q402 (5551) base is high level
The relay cannot
clutch after turning on and there
is no output
Whether Q401 (5551) base is 0V
Q401 (5551) NG
Whether U701 (LC75347) (44) is low level
Q403 ZD402 or VL power supply is in open state
Whether Q701 (8050) is punctured
Change Q701 (8050)
Check the control part according to the check way and steps for
there being no output
Q402 、 JK401A NG or VH+JK power
supply is not normal
Whether Q403 (5551)
collector
is low level