Twisted Sounds 8.5k

[mnhiphop101]

I've got the power supply up and running and I have the correct rail voltages but I cant get it to oscillate even when I drive a sine wave into it. I've replaced both 21844s chips twice and checked all of the a1715 and c2814 transistors.

 

[mnhiphop101]

I've also replaced the 1a , 2a, 2d and max transistors on the driver board

 

[Perry Babin]

Are you seeing the drive on the output terminals of U3 and U4?

Is the opto-coupler that's in front of the driver board shorted from terminals 1-2? From 3-4?

If the marking behind the driver board tell the pin configuration, post a photo of them.

 

[mnhiphop101]

No I am not seeing any drive on u3 and ur

The opti-coupler is not shorted

No marking behind diver board

 

[Perry Babin]

Have you operated all pots and switches through their entire range while monitoring the output of U4 to see if the signal ever passes through to that point?

 

[mnhiphop101]

So I have an ac squarewave now but it's only 5v. On both lowsides

 

[Perry Babin]

That's normal. To have high-side drive, you either have to supply high-side voltage with an isolated power supply (I use a 9v battery) or install the FETs.

5v measured with a multimeter or 5v of amplitude as seen on a scope?

 

[mnhiphop101]

Measured with a scope plus 440

 

[mnhiphop101]

So if I have the correct rail voltage and a 5v ac squarewave is it safe to install fets?

 

[Perry Babin]

I'm sorry but that means nothing.

Did you see a waveform that was 2 divisions tall with the scope set to 5v/div? Or was it only 1 division tall on 5v/div?

 

[mnhiphop101]

Ok so if I go off the scope the wave I much larger

 

[Perry Babin]

If you don't take the time to clearly explain what you're seeing (in detail),it makes it difficult to help. We're working blind. All we have is what you give us. Post a good quality image of the waveform showing what you have and include the scope settings, including probe 1/10x setting.

 

[mnhiphop101]

Ok so when I play a sine wave without the fets in I see the signal on the gate pads on the low sides but when I put the fets in the signal is gone. Nothing is heating up and it idles at 4 amps.

 

[Perry Babin]

Are you installing the FETs in both the high and low sides?

 

[mnhiphop101]

Yes

 

[Perry Babin]

Do you see the signal on the input of the driver ICs?

 

[mnhiphop101]

If the signal is on the gate pads for the fets doesnt that mean there is signal on the drive ic's?

 

[Perry Babin]

Clarify. Didn't you state that the drive signal disappeared when you installed the FETs?

 

[mnhiphop101]

Yes sir you are correct. I took the fets out. Should I put one in each bank and check?

 

[Perry Babin]

You have to have them in both banks.

It's important to know if the drive disappears when the FETs are in the circuit.