Hifonics Brutus BX2200d

[Rabbi]

I Grabbed this amp from a previous owner who tried to repair it, And did a horrible job and i suspect used the wrong output mosfets.

The 12v and ground wires get extremely hot very fast, Assuming its due to high current being drawn.

It draws excessive current (40) at idle with and without remote voltage.


Wondering where to start with this one ?

[Perry Babin]

Have you checked the output transistors?

Does it draw current with no remote voltage applied?

[Rabbi]

it does draw current without the remote wire.

Ive taken a few mosfets off and the current has dropped significantly.
I Had a single Q4469 or O4469 that looked like the former owner added, I removed that so far.

I'm also getting very weak voltage on all rails

[Perry Babin]

Check the rail voltage again (on the center legs of the rectifiers). Place the black probe on the secondary center tap. If you still have very little voltage, post the DC voltage on all of the pins of the KA7500. Place the black meter probe on the amplifier's ground terminal for this. Place the red meter probe on the point where you need to measure the voltage. When measuring the voltage on the KA7500, either monitor the temperature of the heatsink mounted components very closely or clamp them to the heatsink.

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:

[Rabbi]

i went to test ka7500.
Before i had a chance to test the chip, one of my gate resistors blew out. Smoking pretty badly and i got a pop.

The amp was powered on for roughly 5-6 seconds before this happened.

The blue "rear led" did turn on though for the first time since pulling the mosfet that didnt belong on the board to my knowledge (Q4469 or O4469)

[Perry Babin]

It's likely Q, not O. Q is the prefix generally used for transistors.

Was the gate resistor for an output or for a power supply FET?

[Rabbi]

it was a gate resistor for a power supply fet

I got 11.8v rail voltage on both the rails on the output side
No voltage reading on the rails on the power supply side

[Perry Babin]

That sounds like you may have a shorted power transformer.

If the gate resistor failed for one of the power supply FETs, it's likely that all of the power supply FETs have failed.

[Rabbi]

It turns out my power supply was at fault and not the rails.

I now have between 13.93 and 13.96 volts on every rail.

[Perry Babin]

When you use the term 'rail', what precisely are you referring to?