STEG 75.6mx in protect

[nino80]

Hello,

my amp goes in protect-mode. Just connected power + & - & REM -> same state.
I measured the voltage up to the primary winding. After this nothing due to protect.
I dismantled the amp and checked every transistor and they are all ok.

The only bad thing i see that the legs of the transformer (2 on primary and 1 on secondary winding) are a little dark and smells very light burnt.

At this point im stuck. Any help is welcome also circuit diagrams...

Thank you!

[Perry Babin]

Can you post a photo of the board (overall) and the legs of the transformer that appear burned?

[nino80]

Thanks for your reply... measured the windings... no high ohms or shorts...

[Perry Babin]

Check the DC voltage on all of the bridging speaker terminals as you power up the amp. Does any channel pulse high or low as the amp attempts to power up?

[nino80]

no nothing...

[Perry Babin]

Post the DC voltage on all of the pins of the power supply driver IC.

IC#
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:

[nino80]

it is the IC "SG3525AP"... give me some minutes...


thanks...

[nino80]

The DC Voltage on all of the pins of the power supply driver IC.

IC# SG3525AP
Pin 1: 0 V
Pin 2: 0 V
Pin 3: 0,009 V
Pin 4: 0 V
Pin 5: 13,68 V
Pin 6: 0,008 V
Pin 7: 0,019 V
Pin 8: 0 V
Pin 9: 0 V
Pin 10: 0 V
Pin 11: 0 V
Pin 12: 0 V
Pin 13: 0,005 V
Pin 14: 0 V
Pin 15: 0,005 V
Pin 16: -0,196 V

[Perry Babin]

Was the amp in protect mode when you measured the voltage?

Are you sure you have the pin numbering correct?

[nino80]

yes, it was in protect-mode...

numbering according to the datasheet

1 16
2 15
3 14
4 13
5 12
6 11
7 10
8 9