Hello, I am in the process of repairing an amplifier for learning purposes. I am having problems finding the right transistors to drive irf3205 using the tl494.

The tl494 is using the collectors as the 12v input. outputs are on the emitters. Each output is running to two 1k resistors. Each resistor is running to (what I'm sure is) the base of two transistors.


There are two sets of two resistors on the outputs of the tl494. There are four sets of two transistors after the resistors.


What I think is the emitters of each set of transistors are connected together (x4) running to the 47ohm gate resistors of each bank of irf3205.


The smd transistors that are being used are unidentifiable, any suggestions on what transistors I should replace them with will be greatly appreciated.


If needing any more information, I will do my best to give. Thank you.

 

Hello, I am in the process of repairing an amplifier for learning purposes. I am having problems finding the right transistors to drive irf3205 using the tl494.

The tl494 is using the collectors as the 12v input. outputs are on the emitters. Each output is running to two 1k resistors. Each resistor is running to (what I'm sure is) the base of two transistors.


There are two sets of two resistors on the outputs of the tl494. There are four sets of two transistors after the resistors.


What I think is the emitters of each set of transistors are connected together (x4) running to the 47ohm gate resistors of each bank of irf3205.


The smd transistors that are being used are unidentifiable, any suggestions on what transistors I should replace them with will be greatly appreciated.


If needing any more information, I will do my best to give. Thank you.

Each pair of transistors will be a complementary emitter follower. Use BC817/BC807 or 2N4401/2N4403, but first check that they are available in the right case and the pin out is correct.
There should also be resistors from the TL494 outputs to ground.

 

Each pair of transistors will be a complementary emitter follower. Use BC817/BC807 or 2N4401/2N4403, but first check that they are available in the right case and the pin out is correct.
There should also be resistors from the TL494 outputs to ground.

Thank you for the suggestions.

I also thought that there should be a high value resistor on each output of the tl494. There is not, I have removed the tl494 from the board to check under it for traces I possibly couldn't see, there weren't any coming from the (emitters) outputs, only traces are going straight to the two sets of 1k resistors, straight to the bases of each set of four transistors.


I have removed all of the transistors that drive the irf3205 mosfets, to check the output of the tl494, output is fine. Almost 12v.

I took what I thought was the same transistors from another amp and installed them. Amp still doesn't go to protect mode. But the output signals went from almost 12v to about 1.5v. frequency stayed the same each time I tested.