Yamaha AP-U70 Service Manual - Page 8

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Yamaha AP-U70 Service Manual
AP-U70
When the protection function works and the power is turned off after DIAG was started
When the protection function (*2) works, its history appears in the abbreviated form as described below and
the power turns off. Correct the failure based on the history of the protection function.
(*2) When an excessive current or something abnormal in the power source, DC, etc. is detected, the power
is forced to turn off as a protection function.
AmpPt I
display
(Turning on the power without solving the problem causes the protection
function to work at that moment and the power turns off immediately.)
Possible cause: An excessive electric current flow to the power amplifier
Supplementary information: The current of the power IC (IC9) is
detected.
PT PS
display
(Turning on the power without solving the problem causes the protection
function to work at that moment and the power turns off. If the trouble is
in the power supply related to the display, display may disappear.)
Possible cause: An abnormality in the power supply section (voltage)
Supplementary information: As the following power supply is detected,
the faulty point can be identified.
Transformer secondary winding
RE X 2(CB10)
Stabilizing power source
±15A, +9V, +5A, +5D SW, -VP
AmpPtDc
display
(Turning on the power without solving the problem causes the protection
function to work at that moment and the power turns off.)
Possible cause: DC output of the power amplifier detected.
Besides the above possible causes, the cause may be disconnection of the connector, an error around CPU, etc.
G History of protection
When the protection function has worked, its history is stored in the backup memory. Even if no abnormality is found while servicing,
the abnormality the user experienced can be identified by using the data in the backup memory.
The recorded history of the protection function is cleared when the DIAG function is cancelled by setting DIAG menu No.7 INIT to
"MEMORY" (memory initialization) or when the backup memory is erased.
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