Hifonics BRUTUS BX1500D Problem

[blabay]

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

 

[Perry Babin]

You're unlikely to find a schematic diagram for this amp.

The amp has only a positive rail for the outputs. It has both positive and negative 15v rails for the preamp section.

Does the relay engage?

Does the HIP4080 get hot quickly?

 

[blabay]

The relay enagages after two or three seconds and the 4080 barely gets warm. It's drawing 1.3A at idle.

 

[Perry Babin]

Have you tried operating all of the switches and pots (the ones on the front panel) through their entire range to see if audio would play through?

 

[blabay]

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.

 

[Perry Babin]

Do you have ~6v DC on those terminals?

5 is a square wave. 6 is a triangle waveform and 7 is audio.

 

[blabay]

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.

 

[Perry Babin]

What is the DC voltage on pins 2 and 3?

 

[blabay]

Here are the DC voltages on each pin:
1. 12v
2. 12.61v
3. 12.62v
4. 0 v
5. 6.36v
6. 6.65v
7. 6.81v
8. 5.21v
9. 5.21v
10. 11.98v
11. 11.97v
12. 8.82v
13. 0v
14. 0v
15. 12.65v
16. 12.65v
17. 0v
18. 0v
19. 8.83v
20. 8.83v

 

[Perry Babin]

If pin 3 is near 12v, the protect LED should be on. Are you sure its off?

 

[blabay]

I'll take another look, but there are two led's. Power on top and protect on the bottom. The power led is red and the protect led is off.

 

[Perry Babin]

If that's true, post the DC voltage on all 3 legs of Q105.

 

[Perry Babin]

Email me if you want that sony manual.

babin_perry@yahoo.com

 

[blabay]

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.

 

[Perry Babin]

Disconnect the amp from the 12v power supply and remove the HIP4080. It's important that you have a 10 amp fuse in the B+ line before applying power to the amp. You should also have all transistors clamped tightly to the heatsink.

Does the amp still go into protect mode?

 

[blabay]

The green light comes on and the idle current doesn't get above 1.35a
Is the HIP4080 bad?

 

[Perry Babin]

Did the relay engage?

 

[blabay]

Yes, it did.

 

[Perry Babin]

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.

 

[blabay]

I replaced the 4080 and it seems to work! I haven't looked at the output on a scope yet, but it passes the listening test.
I appreciate all your help. You apparently have quite a grasp on car audio.