Audio Art 260.6XE

[caraudioguy2100]

Anyone know what power supply fets I can use in this amp .

It came to me with them removed .

 

[Perry Babin]

What are they using for a drive circuit?

 

[caraudioguy2100]

22ohm gate resistors
TL494CN
A733 and C945 as the drivers

 

[Perry Babin]

If they're using an EF pair for drivers, you can use most anything. The IRF3205s are a common sub. If all of the 22 ohm gate resistors are within tolerance. If you need to replace one or more, use 47 ohm for all of the gate resistors.

 

[caraudioguy2100]

Is there a good replacement for the A733 and C945 transistors they are being used as drivers in the power supply

 

[Perry Babin]

BD139/140

 

[caraudioguy2100]

Would the A1023 and C1027 work as well ?

I have no 139/140’s left have to order some .

Also if I use the Z44N’s as the power supply fets will the 47 ohm resistors be ok or should I switch the back to 22 ohm

 

[Perry Babin]

I've never seen a drive circuit where the Z44s need anything lower than 47 ohm.

The 1023/1027 will work.

 

[caraudioguy2100]

Replaced the driver transistors and the amp still draws excessive current .

The power supply fets get red hot within 2 secs

 

[Perry Babin]

Did you check the drive signals before installing the FETs?

Does it do the same with the rectifiers removed?

If the FETs are clamped to the heatsink and you power through a limiter, does twisting the transformer make a difference?

 

[caraudioguy2100]

This is with no power supply fets installed this is what I get at the gate resistors

Scope is set to 5us 10volts/div

 

[Perry Babin]

Without being referenced to the reference line and the scope set to DC coupling, that means nothing.

 

[caraudioguy2100]

The line was centered that’s what I got when I touched the probe to the gate resistor and the scope is set to dc coupling .

I will try it again .

 

[Perry Babin]

Is the channel set to invert?

 

[caraudioguy2100]

Ok I see what the problem was I didn’t have the probe grounded .

Scope settings are 5us 5volts/div

 

[Perry Babin]

I'm assuming that the FETs have been removed. Load the FET location with something like a 0.1uF cap (gate to source) to see what it looks like.

 

[caraudioguy2100]

Same settings on the scope :

When I load it with a 0.1 if cap gate to source this is what I get

 

[Perry Babin]

I generally use a 0.047uF but that looks much flatter than it should be. The following are before and after being loaded with a 0.047. If you don't have one, two 0.1s in series give you the same thing. Note the scope settings.

 

[caraudioguy2100]

In series you mean 2 of them gate to source or 1 leg of 1 to hate and 1 leg to source and other legs connected together

 

[Perry Babin]

Two caps. One with a leg in the gate. The other with a leg in the source. The two free legs soldered together.