Hifonics BRUTUS BX1500D Problem

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mika111

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Joined 2013
#1
Monacor Carpower Power 1/1000 Problem

Hi!
I would really need some help fixing this amplifier.
The amp came to me as broken and I replaced those power FETs, amp FETs, HIP, flip flop, power Fets control transistors and every little electrolytic capasitors to Rubycon ZL ones (not any big ones on the powerlines they are old ones)...also replaced TL494 pwm and those transition protection diodes on HIP are new.

The amp powers up, but the power led (not protect) lights up red and no sound from speaker output. There is 22mVDC noise at the speaker output when no load is present, and drops to 0V when i connect 2ohm resistor to the speaker output.

I tried to add 4700uF capasitor straight to the amps B+/ground terminals and it seems to operate -> power led turns to green but it draws amperes like pumbing and the green power led´s brightness varies.

I would really need an adwice with this one.....

Sorry for my bad english 🙂

Thank you!
 
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#2
Sorry, I didn´t find out how to edit my previous post...

but that condenser -trick did work only once..now we are at the same point -> power led is red. But something happened because now there is ~1VDC at speaker output when no load is added to speaker terminals.

Also, I cannot measure those amp FETs anymore with multimeter..meter in ohm area -> it´s switching between ´overlimit´ and ´no value´. Meter is Fluke 179.

Either I´m not sure if the transient voltage diodes I changed, were P6KE75a or P6KE7.5a because the markings were a bit lost 😀 Although the voltage at those diodes is ~9,7VDC so i suppose they should´ve been 7.5V diodes or there is some problem in that area?
 
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#8
I just remembered that there was for some reason added P6KE91 -diodes to those amp FETs..I removed them because I don't like putting anything unneccessary things in amplifier. It looked like they were added there latter by somebody. What could be the reason for this..and should I re-place them?
 
#9
Sounds like an issue I was having with the Bxi 2010d. I had 4 of the 2200uf 100v capacitors were causing no audio. They tested out at around 1900uf and took me forever to figure out they were bad because I dont usually suspect caps unless they look bulged or worn. This was of couse after I finally got it out of protect mode after replacing the tl092's.
 
#11
I've been wonderin those caps too..I will change them next weekend, shouldn't be bad idea anyhow 🙂 The P6KEs were, I don't know if I can explain this in U.S but lets try...at the first amp FET is 22ohm resistor+diode -paggages, there are two resistors and two diodes in series (if someone has Brutus or Carpower scematic you should see them there)..over that first resistor+diode -paggage were that P6KE91a, on both sides of that amp same 'situation'. The P6KE was assembled anode towards irf3415, if I remember right. Hope you get something out of my puke 😀
 
#13
Okay..so removing those should do no harm?

You Perry seem to know a lot about these..were would you start finding out the problem? Or do you have an idea what could cause this kind of behavior? What bothers me is that there is some resistors and a op-amp that warms up a bit, but I did not find any reason for that.

http://kuvaton.com/k/YNRL.jpg

I think these are the parts (inside the red circle) getting a little warm....but not 100% sure about this.
 
#18
Expect large resistors to get hot. They're large because they are required to dissipate significant power.

The op-amp may be heating up from the adjacent resistors.

To understand where the P6KE91s were installed, the resolution would have to be much better and you'd have to show the exact point where the terminals were soldered to the board.
 
#19
I believe that this was the point were P6KE:s were installed..schematic is from hifonics brutus so in this case there are 6 pieces of amp FETs per side. I draw only one diode, but there was one on each side of the amp. And only at the first FET looking from preamp.

http://kuvaton.com/k/Y5Yq.jpg

The op-amp heats like pulses..all the time little warm and after few seconds so hot that you cannot hold hand on it...then cools down again and so on. If I measure that op-amp with multimeter, resistance between pins 8 and 3 is only 46ohms..this is little confusing and I cannot find out why the resistance is so low. Also those two comparators have 46ohms between legs 8 and 2

E: Eh..newer mind, I think I found it. Resistor R29C in hifonics schematic 47ohms..so wasn´t anything there either.
 
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