Hifonics Brutus sounds like ol' shortwave radio

[1moreamp]

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

[shize]

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.

[valterdaw]

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.

[1moreamp]

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.

[shize]

i am having trouble understanding what would be considered a dead power fet. I've tried a couple of methods but dont know what i am looking for, is there a way to test and get a good/bad result for differently rated transistors?

[1moreamp]

Originally posted by shize
i am having trouble understanding what would be considered a dead power fet. I've tried a couple of methods but dont know what i am looking for, is there a way to test and get a good/bad result for differently rated transistors?

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