Boston Acoustics GT-40

[mike49504]

Amp came in with 2 blown outputs.. I removed all outputs to test them ..

Outputs are out of the amp right now amp is still stuck in protection mode..

Heres what i get on the SG3525

Pin 1:0
Pin 2:5.18
Pin 3:0.02
Pin 4:0.26
Pin 5:2.06
Pin 6:1.42
Pin 7:2.04
Pin 8:4.92
Pin 9:6.10
Pin 10:0
Pin 11:5.86
Pin 12:0
Pin 13:13.88
Pin 14:5.77
Pin 15:13.64
Pin 16:5.18

Any ideas?

[Perry Babin]

The power supply appears to be working. Does it have rail voltage.

If so, post the DC voltage on all of the pins of the LM339.


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:

[mike49504]

Pin 1: 8.75
Pin 2: 6.95
Pin 3: 13.71
Pin 4: 2.68
Pin 5: 8.74
Pin 6: 5.62
Pin 7: 9.09
Pin 8: 6.96
Pin 9: 8.74
Pin 10: 2.34
Pin 11: 0.49
Pin 12: 0
Pin 13: 0.28
Pin 14: 2.34

[Perry Babin]

Can you take a 'good quality' photo of the bottom of the board under the 339 showing a couple of inches of the board around that area?

[mike49504]

Heres 2 pics of the area around the Lm339

[Perry Babin]

What pin(s) on the 339 read 0 ohms to the cathode of D18?

Is the power LED lit?

What is the DC voltage across DZ5?

[pergo]

those boards seem to be projected by Audiosystem(Steg)'s engineers.

Possibile?

[Perry Babin]

Steg and Twister both use circuits similar to this one.

[pergo]

if you have the schematic or block diagram, can you send me at pergo88 @ alice . it (without spaces..it's for anti-spam ) ?
Here in Italy i cannot find Twister's and Steg's schematics

[mike49504]

Pin 1 Pin 5 Pin 9 all show about 1.1 ohms to the cathode side or D18

Power led ans the led safe light are both lit..

voltage across DZ5 :4.89 volts