KA7500bd Pin 1 high??? Brutus BXi2607D

[Deadly Sones]

I'm working on a Hifonics Brutus BXi2607D. When I apply power and remote there is no excessive current draw as of yet... then again there is not much on.

The power transistors have 0v, 12v, 0v on the legs.

KA7500BD chip has the following readings: (All DC)

Pin 1: 6.12v (really high)
Pin 2: 2.52v
Pin 3: 4.65v (obviously causing the protection to trigger)
Pin 4: 3.95v (close to 3.5v but still a little high)
Pin 5: 1.53v (good)
Pin 6: 3.62v (not sure)
Pin 7: 0.00v (good)
Pin 8: 12.82v (good)
Pin 9: 0.00v (shut off due to protection)
Pin 10: 0.00v (shut off due to protection)
Pin 11: 12.81v (good)
Pin 12: 12.81v (good)
Pin 13: 4.9v (good)
Pin 14: 4.9v (good)
Pin 15: 4.9v (good)
Pin 16: 0.00v (good)

So from what I've been learning the Pin 1 is fed by a positive source and then some divider (assuming a resistor) drops to the proper voltage. Or something sends the required voltage to this pin. 6.12v is obviously really high causing the amp to go into protection.

What should I check for the high voltage problem on pin 1? If this is covered farther in your tutorial Perry feel free to direct me to a page. Your right, its A LOT of material. lol. I'm about half way there and loving it.

I looked for a schematic to try and follow the circuit but wasn't able to locate one.

Thanks in advance for anyones help,
Paul

[Perry Babin]

Can you post a photo of the driver board so I can see which one it is?

[Deadly Sones]

Lol, I just thought of that... was trying to get a good one.

[Perry Babin]

Post the voltage on the LM293.


Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:

[Deadly Sones]

Originally Posted by Perry Babin

Post the voltage on the LM293.

Pin 1: 6.72v (double checked)
Pin 2: 2.46v
Pin 3: 9.82v (double checked)
Pin 4: 0.00v
Pin 5: 1.02v (double checked)
Pin 6: 3.03v
Pin 7: .175v (double checked)
Pin 8:12.82v

[Perry Babin]

When I get back in the shop, I'll see if I have an amp with this board to see If I can point you in the right direction. If you want to try to trace it back, it's likely pin 3 that's being driven. Follow the traces (likely via resistors) to see what drives this on the main board. It may be thermistors.

[Perry Babin]

I don't see anything here. Follow the circuit back to see where it goes.

[Deadly Sones]

O.K. thanks Perry. Should I be tracing pin 3 from the card itself, the 293, or the 7500?

I checked the thermistor in the power supply side and it reads 8.72k ohms.

[Deadly Sones]

Pin 3 from the board goes forward through a cap and 2 resistors then travels all over, it also seems to be connected to the audio driver board.

[Perry Babin]

Pin 3 from the 293.