Hifonics Brutus bxi2000

[ultra]

This amp came in for repair.
Upon starting up goes to protect instantly.
The power supply seems to be ok, since i can measure 100V before voltage starts to go down due to amp going to prot mode.
Checked the preamp, voltage regulators, seem fine, removed all IRF640Ns, none was bad.
Tried to start up without them, but again goes to protect.

[timwebb]

check the drivers on the output driver card.

[mike49504]

Tim's correct pull the output driverboard and the amp should power up fine..

Thoose amps are common for the SMD transistors failing on the output driverboard..

[ultra]

Thank you both for your reply.
I will get some MMBTA42 and 92 on Monday and post back.

[ultra]

Good news, MMBTA42 and MMBTA92 came on Friday.
I also replaced the three SOT223, just in case.
Now, amp works fine.
Thank you.

[Perry Babin]

Q6 and Q7 (on this board) commonly fail and will fail again if you don't take steps to keep them cool. You probably noticed that the board was discolored under the transistors from heat stress. This is a common problem that's been covered in various other threads. On the other boards, Q6/7 are designated as Q1/2 but you can't see the Q1/Q2 designations until you remove the two transistors.

[ultra]

Thanks for the feedback Perry.

All 11 transistors were replaced on this board.

After removing the parts with a hot air rework station, and cleaning everything

with acetone, i checked the board with a strong stereo microscope,

and didnt see any signs of heating on the board.

So i soldered the new parts (too afraid to use the hot air yet, as i am very new

to this).

[ultra]

Finally, you were right Perry.

It lasted only a couple of minutes.

So, whats the solution to keeping the transistors cool,

swap them with TO-92 devices?

I didnt find any info while searching for "hifonics brutus".

[Perry Babin]

They shouldn't fail that quickly. They fail but generally only after several months. If they fail within a few minutes, there is another problem. Q6 and Q7 are in parallel. Are you sure that they were both soldered to the board? I'm assuming that those are the ones that failed because they are the ones that most commonly fail.

[ultra]

The problem is different now.

With the rca connected the amp goes to protect.

Without them, it powers up fine.

I measured the output rca shield with the power gnd and showed 0 ohms.

This did not apply for the input rca. Upon grounding the input rca shield,

powers up fine.

I am worried about Q6 and Q7 though. Should i do something before giving the

amp back?