Directed 2400D

[mike49504]

I got one of theese in for repair.. The power supply fets were blown outputs were bad..

After removing all the bad fets and the power supply driverboard and the reverse polarity diodes..

The amp is showing 0.3 ohms from middle leg to 3rd leg on the power supply fet pads..

I made sure there is no solder bridges between the pads..

Any ideas??

 

[Perry Babin]

Assuming that you've carefully checked for solder bridges, you may have a shorted transformer. Try twisting them while measuring the resistance to see if that clears the short.

 

[mike49504]

Tryed twisting both transformers and no cjange at all still reads shorted and still stays at 0.3 ohms..


If a filter cap was shorted would that cause this issue or is it more likely to be a shorted transformer?

 

[Perry Babin]

If the short didn't clear, it's not likely to be a transformer. Is either secondary center tap directly connected to ground?

Did you remove all of the flux from the solder pads and look for bridges with a lighted magnifying glass?

It could be a shorted filter cap. It's rare but it can happen.

 

[mike49504]

Looked at all solder pads no bridges ..


Removed all filter caps ..


Secondary center tap doesnt appear to be directly connected to ground


Amp still shows shorted between legs 2 and 3

 

[timwebb]

the one i just fixed did the same thing. but it still powered up and the amp worked. i just replaced it all.

 

[Perry Babin]

Does anything look like it got hot enough to melt solder so that it could have dripped down the board?

This sometimes happens on the power and ground terminals. It could be on the top or the bottom of the board.

Is there possibly a wire strand melted into the plastic of the terminal block creating a short?