Directed 2400D

[caraudioguy2100]

Anyone know of a good replacement for the FB31N20’s ?

Also does this amp use both fb31n20’s and 9640’s?

Someone was inside this amp and it has all mismatched outputs in it

 

[Maxikill97]

A similar amp (GZPA1.3000D) had the IRF640 and IRF9640

 

[Perry Babin]

Try both the IRF640 and IRF640N. The N may run cooler.

 

[caraudioguy2100]

Will the BD139/140 work in the power supply section for the drivers ?

 

[Perry Babin]

Yes.

 

[caraudioguy2100]

Here are the drive signals for the power supply fets .

With all outputs out of circuit the amp still draws excessive current.

I have a 0.1 uf cap connected between gate and source .

Scope settings are 10us 1volt/div

Do these appear ok or is there a drive problem
To the fets ?

 

[Perry Babin]

Those don't look like there is a capacitor connected. When a capacitor is gate-source, you'd expect the same curve on both the top and bottom of the waveform.

 

[caraudioguy2100]

Should I replace the drivers again ?

I double checked my connections and they are solid connection on the 0.1 cap between gate and source

 

[caraudioguy2100]

Replaced all of the transistors on the power supply driver board .

Same issue the drive signals doesn’t change .

Any ideas ?

 

[Perry Babin]

Do you see any signal on the source pads?

What is the measured value of the gate resistors?

 

[caraudioguy2100]

First pic is gate pad
2nd pic is of source pad

And the gate resistors measure 22.3 ohms

This is with a 0.1 uf cap between gate and source .

Scope set to 10us 1volts/div

 

[Perry Babin]

I don't understand why a 0.1uF cap is causing the waveform to charge and discharge slowly.

Attached is more of what I'd expect.

 

[caraudioguy2100]

Could i possibly have a bad 494 ?

Or any ideas on what to check ?

Not sure why this is happening either but the amp will draw excessive current and fets get hot within 2 secs

 

[Perry Babin]

Do you have a meter to confirm that the 0.1uF capacitor is within tolerance?

Did you try twisting the transformer to see if that made a difference?

I'm assuming that you removed the rectifiers to isolate the supply.

 

[caraudioguy2100]

Rectifiers are removed .

The cap measures good

I tried twisting the transformers no change .

Here is what the drive signals looks like with a fet installed instead
Of the cap

Scope set to 10us 1volt/div

 

[Perry Babin]

That looks OK. What does the other bank look like?

The scope may be at 1v/div but the probe is on 10x, correct?

 

[caraudioguy2100]

Here is the other bank .

The scope is set to 10us 1volt/div

The probe is set at 1x not 10x

2nd pic is of another bank of fets . This is the bank I’m having the most issues with .

Here is what I get on the scope with 1 fet installed in the bank .

 

[Perry Babin]

What's the DC voltage on the collector of the NPN driver transistor?

 

[caraudioguy2100]

I found that one of the transformers was shorted .

Without any outputs in the amp right now I get -45 volts of rail but +65 volts of rail .

Should I put the outputs back in circuit and see if that changes anything ?

 

[Perry Babin]

Are you using the secondary ground as the reference?