Bought dead Brutus from ebay just for fun (BX1500D). It had a driver IC burnt from overheating or reverse polarity, who knows. All FET's seems to be fine... Now it works, puts a full power, a lots of power 
The only problem that it has a high frequency sound noise (actually very entertaining signal), variable, just like very old shortwave radio when you are tuning it, not loud, and not very noticable with sub, but still annoying. What it can be, and where to look at
The only problem that it has a high frequency sound noise (actually very entertaining signal), variable, just like very old shortwave radio when you are tuning it, not loud, and not very noticable with sub, but still annoying. What it can be, and where to look at If the noise is barely audible and not related to engine speed, it's likely that it's due to the interaction of the two oscillators (one for the PS and one for the class D audio section). Some amps synchronize the two oscillators to prevent this. I don't think it's possible with the TLx94 IC (which is what I believe that amp uses). Amps that use the SG352x IC often have the oscillators sync'd.
If all of the filter caps at the output are OK and there are no shorted inductors, it could be normal for that amp.
If all of the filter caps at the output are OK and there are no shorted inductors, it could be normal for that amp.
If I'm not mistaken, when the TLx94 IC is slaved, it simply uses the master IC's oscillator instead of its own on-board oscillator.
The on-board oscillator is a sawtooth waveform, it would be somewhat difficult to derive that from the class D section's signals. In a typical amp, you'd have to divide the frequency, produce the sawtooth waveform (could be done from the integrator output on some amps) and then change the level to suit the TLx94 IC's logic section.
The on-board oscillator is a sawtooth waveform, it would be somewhat difficult to derive that from the class D section's signals. In a typical amp, you'd have to divide the frequency, produce the sawtooth waveform (could be done from the integrator output on some amps) and then change the level to suit the TLx94 IC's logic section.
OK, it's technically possible but not practical and as far as I know it's not done in any commercially available amplifier that uses the TLx94 IC.
If someone knows of an amplifier using the TLx94 IC that syncs the class D oscillator to the power supply oscillator, please post the make/model. I'd like to see how they do it. I'm always willing to learn something new.
If someone knows of an amplifier using the TLx94 IC that syncs the class D oscillator to the power supply oscillator, please post the make/model. I'd like to see how they do it. I'm always willing to learn something new.
I looked on the schematic for your brutus and sync'ing is not the problem, as I see it.
Pull your Rca's , does the noise go away ?
Start checking all the caps in the D section around the LM833's and the HIP4080AIP, all the way back to the cmos oscillator.
Also check for a burnt ground resistor back near the power supply you can't miss it as its always overheated and near the toroid.
These normally fail because of lead frame failure. The leads on the output fets literally break off inside the TO-220 case where you can't see them. ( way too much clamping pressure on the fets )
If you attempt to remove the fets from the grip of the sil-pad you will usually see a lead just simple snap off at the case edge.
The failure causes the fets on the output stage to ramp to full turn on, and causes a shorted condition ( the gate lead usaully causes this condition).
I have one I just repaired for this condition, works great now with a new set of outputs and some silicone grease to the pads to give some slip on the cases. Plus I have seen a bunch like this, and it does appear to be the main failure I have seen so far over the last 25 or so I have repaired.
Your problem appears as a noise related issue in the front end of the amp. I have seen similar problems on Tripath designs and other brands,
Funny though the amp does not have a bandwidth to reproduce 10 to 15 kilo-hertz so its got to be passing right thru the output filter network.
check some of your caps up front. I would be very interested to see your findings.
as always I hope this is found helpful
Pull your Rca's , does the noise go away ?
Start checking all the caps in the D section around the LM833's and the HIP4080AIP, all the way back to the cmos oscillator.
Also check for a burnt ground resistor back near the power supply you can't miss it as its always overheated and near the toroid.
These normally fail because of lead frame failure. The leads on the output fets literally break off inside the TO-220 case where you can't see them. ( way too much clamping pressure on the fets )
If you attempt to remove the fets from the grip of the sil-pad you will usually see a lead just simple snap off at the case edge.
The failure causes the fets on the output stage to ramp to full turn on, and causes a shorted condition ( the gate lead usaully causes this condition).
I have one I just repaired for this condition, works great now with a new set of outputs and some silicone grease to the pads to give some slip on the cases. Plus I have seen a bunch like this, and it does appear to be the main failure I have seen so far over the last 25 or so I have repaired.
Your problem appears as a noise related issue in the front end of the amp. I have seen similar problems on Tripath designs and other brands,
Funny though the amp does not have a bandwidth to reproduce 10 to 15 kilo-hertz so its got to be passing right thru the output filter network.
check some of your caps up front. I would be very interested to see your findings.
as always I hope this is found helpful
I've seen the legs break off of the transistors inside the transistor body on MANY planet audio amps. The problem with the pa amps is that they have insufficient support for the board where the inductors are mounted. When the amp is subjected to vibration, the mass of the inductors causes the board to flex which causes the legs of the transistors to be stressed and eventually break. When the legs break a couple of things can happen, If the gate leg breaks first, it will cause the amp to shut down (if the protection circuit does it's job). If the drain or source legs break first, the parallel transistors will fail when the amp is driven hard.
I've seen a broken gate leg cause techs problems because the problem can cause the amp to intermittantly shut down.
With the clamping systems used in most amps, I don't think it's possible to have enough clamping pressure to damage a transistor (as long as the pressure is evenly applied to the face of the transistor). I've used heatsink clamping systems that used much more pressure and never damaged a transistor. Most amps use a one 3mm screw per two transistors into dead-soft aluminum. The sink will strip well before the transistors are damaged.
The transistors MUST be tightly clamped. I don't want him to think he needs to leave the clamps loose to allow it to move.
I've seen a broken gate leg cause techs problems because the problem can cause the amp to intermittantly shut down.
With the clamping systems used in most amps, I don't think it's possible to have enough clamping pressure to damage a transistor (as long as the pressure is evenly applied to the face of the transistor). I've used heatsink clamping systems that used much more pressure and never damaged a transistor. Most amps use a one 3mm screw per two transistors into dead-soft aluminum. The sink will strip well before the transistors are damaged.
The transistors MUST be tightly clamped. I don't want him to think he needs to leave the clamps loose to allow it to move.
Your all good Perry, I agree. Perhaps I should have been clearer about the use of silicone grease to him.
And yes I have also seen the vibrating circuit card, on Hifonics, and Toxic Audio, and a few others out of that same shop in Hong Kong.
I add rubber feet under the board with a touch of rtv to the board and the case to cut down on the shock issue these amps see.
Lots of poor mechanical assembly coming out of Hong Kong factory's.
The reference to TOO much clamping pressure is valid though as The device can not move with heat induced expansion and contraction of the case. This also pulls the legs off of power devices.
As the case expands it lieterally pulls the lead frame back and forth between the board and the sink clamp.
PPI used a fair system, that needed more spring added to the bottom plate, but it did allow the device to move slightly under expansion and contraction of the case. I never saw lead frame failure on those amps.
Anyway Thanks Perry, I'll try to improve my descriptions in the future
And yes I have also seen the vibrating circuit card, on Hifonics, and Toxic Audio, and a few others out of that same shop in Hong Kong.
I add rubber feet under the board with a touch of rtv to the board and the case to cut down on the shock issue these amps see.
Lots of poor mechanical assembly coming out of Hong Kong factory's.
The reference to TOO much clamping pressure is valid though as The device can not move with heat induced expansion and contraction of the case. This also pulls the legs off of power devices.
As the case expands it lieterally pulls the lead frame back and forth between the board and the sink clamp.
PPI used a fair system, that needed more spring added to the bottom plate, but it did allow the device to move slightly under expansion and contraction of the case. I never saw lead frame failure on those amps.
Anyway Thanks Perry, I'll try to improve my descriptions in the future
Valterdaw,
Which IC did you have to replace? I have this same amplifier but it doesnt completely power up.. the power led stays red instead of turning green like it should. The guy I got it from ran it at .5 ohm till it stopped playing. I cant find anything that looks burned up at all inside... any suggestions? My other bx1500 makes that RF sound you mentioned also, i think they all do it.
Which IC did you have to replace? I have this same amplifier but it doesnt completely power up.. the power led stays red instead of turning green like it should. The guy I got it from ran it at .5 ohm till it stopped playing. I cant find anything that looks burned up at all inside... any suggestions? My other bx1500 makes that RF sound you mentioned also, i think they all do it.
I actually reduced noise from amp by replacing a capacitor in series with resistor, which is supposed to be overheated (one was, one wasn't). Now both are hot as hell and it's working better.
Try checking resistance between FET's leads, this way you can identify internally shorted ones. In my amp FET driver IC (HIP4080AIP) also failed.
Try checking resistance between FET's leads, this way you can identify internally shorted ones. In my amp FET driver IC (HIP4080AIP) also failed.
The HIP4080AIP is fairly sensitive to static and is prown to failure.
This might explain why they are "ALL" mounted in sockets for this type of design.
And I do mean "ALL" of these amps using the HIP4080AIP. They ALL have sockets for easy removal and replacement. Every brand from every source "ALL" have socketed HIP4080IP chips.
This might explain why they are "ALL" mounted in sockets for this type of design.
And I do mean "ALL" of these amps using the HIP4080AIP. They ALL have sockets for easy removal and replacement. Every brand from every source "ALL" have socketed HIP4080IP chips.
shize said:
Well, were talking about semiconductor junctions here. And when a doped PN junction is measured with a ohm meter. It has readings similar to a simple diode junction (i.e. voltage flows one way but not the other).
So you will normally get a reading similar to a diode junction. And of course when you get readings of 1.2 ohms well that's a dead short.
PN junctions fail in only two ways, 1 Shorted, 2 Open.
So it gets real easy after abit of time and training to just ohm out a junction and see whats what with that single device junction.
Now in car amps, the power supply fets are in banks of parallel devices. And because of this measuring one device is like measuring all in that bank of devices. This is where things get abit unique.
Anytime you have paralleled devices (like power supplies, and output stages) You just can't take a reading across any two leads as those leads are connected to other devices directly, so your reading everything all at once.
You should probably lift one of the leads out of circuit, and then measure off that center lead as a common for the other two leads of the device under test.
Now with time and experiance at the bench you will find that semi's short out 99% of the time, and blow open the other 1%.
Armed with this time instilled wisedom you will know when the voltmeter reads below what a normal junction would read that that device might just be shorted.
In most cases Shorted FETs will have very low readings like less than 20 ohms, and typically 1 to 3 ohms
Bad Fets in these amps look like lightning hit them, they are cracked open, and one common thing to all these Brutus amps is lead-frame failure on the output fets.
Hope you find this helpful, and Happy New Year one and all
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