Sundown SAE-1000D

[caraudioguy2100]

Amp is using ST80NF70’s as the power supply fets with 100 ohm gate resistors .

Will the 3205’s work in this amp ?

 

[Perry Babin]

Yes but unless there is a lot of deadtime programmed in, you'll have to go to 47 ohm gate resistors.

 

[caraudioguy2100]

Here is what I get for drive signals .

Do these appear ok ?

Scope set to 5us 5 volts/div

 

[Perry Babin]

That looks OK but doesn't tell you about deadtime. If you install the 3205s and they run hot at idle and full duty cycle (I don't know if this amp has regulation, for the rails), you'll need to replace the gate resistors with a lower value (generally 47 ohms).

 

[caraudioguy2100]

I changed the gate resistors to 47 ohm and put in some 3205’s and the amp draws excessive current

 

[Perry Babin]

Did you try twisting the transformer?

Checked outputs?

Pulled rectifiers?

 

[caraudioguy2100]

I pulled the rectifiers amp still draws excessive current.

Checked the outputs they all test fine .

Tried twisting the transformer no change

 

[Perry Babin]

Measure the frequency at the gate of the FETs.

 

[caraudioguy2100]

Do I do this with the drivers loaded with a cap or unloaded ?

 

[Perry Babin]

Did you pull the 3205s?

Load/no load doesn't matter.

 

[caraudioguy2100]

I pulled the 3205’s

I don’t get any reading on my meter it just stays at 0.000

 

[Perry Babin]

Do you see a drive signal?

Are you sure that the meter is set to read frequency?

 

[caraudioguy2100]

I see drive signals

And yes meter is set to read frequency

 

[Perry Babin]

Test it on your signal generator.

It may not be auto-ranging.

 

[caraudioguy2100]

It works on my signal generator .

I set the signal generator at 100hz and the meter was dead on

 

[Perry Babin]

Try it at 20kHz on your generator.

 

[caraudioguy2100]

The meter says 25khz when I test it on my signal generator

 

[Perry Babin]

Place:

Black on source
Red on gate

 

[caraudioguy2100]

Still nothing

 

[Perry Babin]

Check it on the output terminals of the driver IC.