T1000-1bdcp

[Perry Babin]

Is the rail voltage changing because the output stage is switching on and off?

Are you saying that the 10uF didn't reduce the noise on the speaker terminals?

To get an accurate view of the waveform on the speaker terminals, you may need to connect the ground wire for the scope probe to the negative speaker terminal.

 

[punch45x2]

Perry I did have the ground on the scope to the negative speaker terminal during the test. The rail voltage starts at 85.7vdc at 3.25 amps current draw then rises to 96.2vdc at 3.43 amps in a minute then dropping back down to 90vdc at 3.49 amps in about 60 seconds

 

[punch45x2]

If I turn the gain down the rail voltage is fairly stable at 98vdc 4 amps and gain up is 86.7vdc at 3.5 amps

 

[Perry Babin]

Don't use the gain as a level controller for testing. When troubleshooting, you need to change only one variable at a time. Using the gain involves the gain control and circuit.

If it does this with no input, nothing connected to the RCA jacks, you need to find what changes when the gain control is adjusted. More noise on the output?

Is the output stage switching on and off as the rail voltage changes?

Is the amp producing audio?

 

[punch45x2]

The amp is producing audio. For testing I have no audio input in to the amp. When I am turning the gain up there is notable humming but not when the gain is down.

 

[punch45x2]

How can I tell if the out put stage is turning on or off

 

[punch45x2]

Perry I ha e also noticed that my rail voltage drops to 0vdc after the power has been disconnected.

 

[Perry Babin]

If you have a speaker connected, the hum could be causing the additional current draw.

The rail voltage is going to drop to 0v. If it has the common 3k ohm drain resistors, the voltage is going to drop. How long does it take to drop to 0v after the remote voltage is removed?

Does the hum stop when the rail voltage goes high?

 

[punch45x2]

It does have r1020. It takes about 45 seconds for the rail to drop down. Once it goes below 40vdc the torrid makes the screeching sound till the rail is back up to 85vdc

 

[Perry Babin]

When does the amp make the screeching sound?

With no remote, the output stage should shut down, including the output stage. When remote is applied, the rail voltage should build almost instantly.

 

[punch45x2]

During remote turn on when rail is under 50v.

 

[Perry Babin]

How long does it take to build rail voltage?

Are you allowing enough 12v supply current to allow the amp to power up normally?

 

[punch45x2]

About 1 second.

 

[Perry Babin]

Do you have a delay for the output stage to start oscillating after the power supply starts?

 

[punch45x2]

So there is like a half second delay after rail voltage reaches 96vdc. From 0vdc rail to output stage turn on it is about 2 to 3 seconds

 

[Perry Babin]

Are you saying that the speaker screeches BEFORE the output stage starts to oscillate?

What sort of speaker are you using?

 

[punch45x2]

No the toroid screeches. Not the speaker output.

 

[Perry Babin]

I don't think I'd be concerned about that if the amp performs perfectly, otherwise.

 

[punch45x2]

What are my options to try to rectify that?

 

[Perry Babin]

From what you've told me, I don't see anything wrong.

Is the noise so loud that you'll hear it with the amp closed up and in the trunk?