Those numbers don't look familiar. The MJE4343 and MJE4353 may have been used in some of the amps.
Since one failed, you need to replace (at least) all that were in parallel with the one that failed.
The FJA4313 and FJA4213 may be good subs but you'll have to carefully check the bias through the entire thermal operating range to confirm that the bias holds with those transistors.
Since one failed, you need to replace (at least) all that were in parallel with the one that failed.
The FJA4313 and FJA4213 may be good subs but you'll have to carefully check the bias through the entire thermal operating range to confirm that the bias holds with those transistors.
ok I replaced all the devices in the bad channel,
the amp is now making a loud fizzing - hissing noise.
The noise is coming from the transformer???
the amp is now making a loud fizzing - hissing noise.
The noise is coming from the transformer???
If you reduce the DC voltage feeding the amp, does the noise change?
If you touch the transformer windings, does the noise change?
If you touch the transformer windings, does the noise change?
When I power it up with a current limiter the noise reduces a little.
Q122 has blown again and it's gate resistor is dead
Q122 has blown again and it's gate resistor is dead
What did you install in place of the original transistor?
If you touch the transformer windings, does the noise change?
How loud is 'loud'?
If you touch the transformer windings, does the noise change?
How loud is 'loud'?
Are you sure that they weren't counterfeit?
Did any of the power supply FETs fail?
Were the transistors tightly clamped to the heatsink when the output failed?
Did any of the power supply FETs fail?
Were the transistors tightly clamped to the heatsink when the output failed?
Fakes can have anything printed on them.
Crack open one of the originals and one of the replacements that failed and compare the appearance of the die. If you squeeze them across their width at a slight open in a vise, they will crack open easily.
Crack open one of the originals and one of the replacements that failed and compare the appearance of the die. If you squeeze them across their width at a slight open in a vise, they will crack open easily.
There's definitely a difference.....
Shall pull all the replaced devices and see if it powers up ok?
Shall pull all the replaced devices and see if it powers up ok?
Just pull the shorted ones. Even if they're counterfeit, they should work well enough to test at idle.
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