Output Transistor?

[qtipextra 5,000+ posts]

Are the output transistors big, or are they just about reguar size transistors?

There are a ton of regular sized transistors on the ends of the amp, and then there is this one huge thing that I dont know what it is. (Picure: its where the 2 red wires come together, right under the wires, that black thing)

Which is (are) the output transistor(s)? Where the blue things are on the top and the bottom are where the lots of transistors are.

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[JimJ 5,000+ posts]

They're the ones on the sides...those metal brackets seem to be heat sinks to help thermally couple the MOSFETs to the main heatsink.

 

[squeak9798 5,000+ posts]

Yeah, they'll be towards the outside of the board, and actually make physical contact with the heatsink.

Probably look something like this:

Probably attached to or under those blue metal brackets.

 

[Pyro_By_Nature 5,000+ posts]

I'm not too familure with the BX1000D board, but they're probably the ones on the bottom right.I'll try to find the pic I have of the customers BX1500D, not sure how similar they are.

 

[Pyro_By_Nature 5,000+ posts]

I think that's where they are on the BX1000D as well, if you have AIM I can tell ya how to test them and what to expect (using a DMM, assuming you have one).

 

[JimJ 5,000+ posts]

Ouch...got fire? //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

 

[Pyro_By_Nature 5,000+ posts]

It lasted about 30 min. of testing at 1 ohm........tooooooooooons of smoke //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif

 

[qtipextra 5,000+ posts]

I think that's where they are on the BX1000D as well, if you have AIM I can tell ya how to test them and what to expect (using a DMM, assuming you have one).

Dont have AIM, but I have MSN messenger. I do have a DMM.

If you have MSN, add me, qtipextra@hotmail.com, if not, well, email me or PM or somehting.

I took a basic electronics class, so I know what the transitors look like and everyting, but I dont know how to find out which are working and which ones need to be replaced. I have a bunch of soldering experience on little boards and stuff, so I can get new parts and solder new ones on no problem. I just need to figure out which one(s) are bad.

Thanks

 

[qtipextra 5,000+ posts]

On the first pic that I posted, looking at the bottom, you can see the legs of the bottom transistors sticking out (on the left side of the bottom blue bar thing). There are 4 kinda grouped together there. Is that the ones that is would be, or could it be others to the right of those?

Also, on this site, are those test with the transitors in place on the board, or with them out by them selfs?

 

[thch 10+ year member]

hmm. i'd bet the output transistor are across from the sparsely wound, stacked grey donuts (toroids).

the PSU transistors appear to have burned out in the amp in the posted picture.

as for the MOS devices, the most common failure is for the gate-oxide to break down. for best testing you need to take the device out. under such a condition, no 2 terminals should be connected if the device is good (and not obviously destroyed).

in circuit, test the gate to soure resistance for each transistor. it should come up as a high value, but may come up as something lower if the circuit it is in have a resistor from gate to source.

 

[qtipextra 5,000+ posts]

hmm. i'd bet the output transistor are across from the sparsely wound, stacked grey donuts (toroids).

Are those the 2 coil things that are identical?

So u think there might be 8? The four at the top (above the 1st coil thing), and the four at the bottom (below the second coil thing)?

 

[qtipextra 5,000+ posts]

I just un-soldered and, after testing each, re-soldered the transitors cirlced in the picture.

I did not find any out of those eight that were bad, according to this site, they all should be good.

What else could be the problem?

 

[thch 10+ year member]

it is possible the amps PSU has a bad transistor. I've had a class D amp that had 1 bad transistor.

from the pic, i'm assuming the circled devices are the output transistors -- the devices used in the class D output stage. the grey toriods with loose wrappings are probably the output inductors with combine with the two long blue polyfilm capacitors to give an integrator. the smaller wire wrapped torid is probably a balun transformer.

the red wires take one output to an output terminal of the amp. the other red wire is connected to the relay and amp out. this allows the output to be fully disconnected in case of problems.

i can only assume the long, but oddly unsocked IC near these components is a hip4080, or similar PWM controller/driver.

you can also have problems with the other transistors.