Yamaha DSP-AX620 Service Manual page 12

DSP-AX620
If the protection function activates after DIAG has been started and the power is turned off ;
When the protection function (*2) activates, the protection function history appears on the display and the power
turns off. Repair the faulty parts according to the displayed history.
(*2) When an excess current or any other faulty condition is found with the power source, DC, etc., the protection
function forces the power to turn off.
I PROTECT
PS PRT :000 X
DC PRT :000 X
Besides the above possible causes, the cause may be a disconnected connector or around the CPU.
PS PRT and DC PRT displays include the abnormal A/D value in % (voltage value obtained by considering 5V as
100%). Concerning this value, refer to DIAG menu No.11 AD DATA CHECK described on page 24.
Protection history
When the protection function has activated, its history is stored in memory with a memory backup. Even when no abnormality is
noted while the unit is being serviced, an abnormality which has occurred previously can be defined as long as the backup data has
been stored. The protection history should always be cleared before returning the unit from service.
The protection history is cleared when DIAG is canceled by selecting "RSRV" (memory initialization) from the setting items of the
DIAG menu No.10 FACTORY PRESET or when the backup data is erased.
11
I PROTECT display
X
(When the power is turned on without this abnormality corrected, the pro-
tection function activates the moment the power relay is turned on to shut
off the power relay. The display will not light.)
Cause: There is an abnormal current flow to the power amplifier.
Supplementary information: As the current of the power transistor of
each channel is detected, the abnormal channel can be identified by
checking the current detect transistor.
PS PRT display
(When the power is turned on without this abnormality corrected, the
protection function activates about 1 second later to shut off the power
relay. Display may not light if there is an abnormality with the power supply
for the display.)
Cause: There is an abnormality in the power supply section (voltage).
Supplementary information: As the power from the following sources is
detected, it is possible to determine where an abnormality exists.
Main (5): Transformer secondary winding
Power (3): Regulated power supplies
DC PRT display
(When the power is turned on without this abnormality corrected, the pro-
tection function activates about 3 seconds later to shut off the power relay.)
Cause: A DC output from the power amplifier of any channel is detected.
CB373 (AC voltage)
±12, ±5V, +5D