audiobaun A18001d

Replaced all the z 44's and 2 of the 2807's, amp is going into protection, I can get it to turn on if i turn my astron power supply down to ten volts and the amps down to 2 amps, but then it turns on and off instead of going into protection, if i could get a idea on where to start would be great thanks

I did not install fans yet but do have all the fets secured with thier clips
 
I checked the 4080 ic without power, meter in ohms pins 2 and 4 are 2.4 k pins 15 and 17 are the same these are ground and 12v so seems thats fine. the driver pins 13 and 14 are 154 k as well as 18 and 19 154 k, ic is not shorted, I have not checked it with power applied to get voltage as of yet. the reason I have not applied power is because one of the brand new 2807's I installed already shorted with 5 amps applied, all gate resistors are within tolerance 100 ohms no diodes are shorted.The main power and ground of the amp is 600 ohms red lead in power black in ground
 
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MatthewS

Member
2008-02-22 9:19 pm
These amplifiers, as well as any class D built around that drive chip can be finicky even if you replace the outputs with the exact same parts. I believe it's an HFE issue, but never looked into it further. The last one I touched had the part socketed and you could power the amplifier up without it installed as the gates were pulled down without it. Furthermore, you could do the opposite and remove the outputs and leave the 4080 in and do some power on testing of the gate drives. Take the gate measurements AT the mosfet PADS to rule out breaks in the pads you might not see. Keep at it and nail it down to one section.
 

MatthewS

Member
2008-02-22 9:19 pm
Perhaps, you could help with that by taking some initiative and rechecking your output devices or following the later half of my suggestions. Large devices are expensive, Joe. When I work I tend to remove them and test drive/gate signals and voltages at the pads prior to reinstallation (when it's topographically possible by design). Some people do it differently with current limitations places on the power supply. However since i've started doing things this way I end up with a lot less blown parts on my bench. Pull the outputs out of the amp. Test them out of the amp. If you find a bad one, don't just put the rest back and replace the bad one; find the reason it died first.
 
It's extremely rare that the 4080 survives when the outputs fail.

The only replacement outputs that you're likely to find that work are the IRF3710Z (Z is VERY important).

You should replace all outputs and the 4080 at one time then power it up through a current limiter with all transistors tightly clamped to the heatsink.

It's possible to test the drive signal but it's not as easy as powering the amp up with no outputs. The high-side won't produce a readable signal. You have to ground the input leg of the output filter inductors and the center tap of the power transformer. Even then, you can only test at low frequencies (which doesn't tell you anything about high frequency performance) unless you inject a high frequency signal into the signal line after the crossover.