akira HTS-797AS, Service Manual

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Model No.: HTS-797AS
Version: 1.0
Trouble shooting for amplifier channel’s burning and scorch.
Phenomenon:
Directly examine the channel. The amplifier tube Q513/Q514 has cracked and the emitter output
resistance R528/R530 has burned and been in the open state.
Analysis:
It may be the over current or voltage or the short circuit of back speaker lines when there is a big
volume output or the quality problem of circuit apparatus to cause the burning of the amplifier.
Trouble shooting way and steps:
First take away the burned amplifier tube Q513 and Q514 to change R528 and R530.Then check the
amplifier output through electricity test to see whether it is 0v.If far from 0v too much, normally it is
the driving or the voltage amplifying or the differential
amplifying tube that has been punctured. After
confirming the output is 0v, we need to test whether the base jointing point of Q513 and Q514 is
between 0.4 to 0.6v.If so, then we can install the amplifier tubes again. Otherwise we cannot install
until the problem is solved.
Trouble shooting way for turning on protection trouble.
Phenomenon:
The machince’s display is normal after turning on but automatically turns off when initialization is
finished.
Analysis:
It approves that the turning on and turning off circuit is normal if this unit powers off after working
normally for several seconds. The problem maybe exist in the amplifier or the protection circuit.
Trouble shooting way and steps:
Over voltage protection check:
In the moment of being electrified and before this unit enters the protection mode, use the volts DC of
multi meter to test the output of each channel, which cannot - 0.5v.If one certain channel’s
voltage is obviously over its range, it approves that there exits problem with this channel’s amplifier
circuit. So you should place emphasis on checking if there is some apparatus in this channel, which
has been punctured.