Hifonics BRUTUS BX1500D Problem

blabay

Member
2010-11-10 2:57 am
Several Mosfets and two dual diodes had broken leads on one side of the amp. I replaced them and checked the rest. Found no more broken leads. The amp powers up and comes out of protect but doesn't pass audio. I checked the low voltage supply, but I'm not sure what to check next. Are there supposed to be symetrical high voltage rails? I found +59 volts on the diodes, but no negative 59 volts. DC voltages on the mosfets on both sides of the amp match and it doesn't seem to be drawing excessive current. My 12v supply is only 5A and doesn't sag when the amp powers up. Does anyone know where I can find a schematic for this amp?
Thanks
 

blabay

Member
2010-11-10 2:57 am
Yes. I have a scope and traced signal to the HIP4080. I see three signals on this chip. on pins 5,6,7 I see the audio, and two pins have high frequency oscillation. Looking at the datasheet for this IC, it appears to be dead. It seems to have input, but no drive signal for the mosfets. I'm going to check some more things. Make sure it has Vdd, etc.
 

blabay

Member
2010-11-10 2:57 am
That is exactly what I see there. I don't see any thing on the outputs however. The IC has 12vdc at the appropriate pins. Shouldn't the drive output be a modulated square wave? I see only a tiny amount of noise on the drive outputs that doesn't change with change in input level/frequency.
 

blabay

Member
2010-11-10 2:57 am
The voltage on leads 1,2,3 of Q105 is 11.4, 12.55, 12.06 respectively.

I noticed that the power LED is dual color. Looking over the O/M it states that the LED should be Green, not red. It also talks about a "diagnostic" mode, but doesn't say how this mode is indicated. I'm guessing its the red power LED.
Hopefully this info helps.
 
If the DC voltage on both the positive and negative speaker terminals is 0v (black probe on the amp's ground terminal) after the relay engages, it's very likely that the 4080 is defective. Push on various points on the board to make sure the voltage remains at 0v.

Before ordering the 4080, check 1 more thing. Reinstall the 4080 and connect a 1000uF (or greater) directly across the B+ and ground terminals on the amp. If the amp again goes into protect, replace the 4080.