speed3:
Does the amp make the high frequency noise with no RCAs plugged in?
When you drive the amp to a moderate level (with a speaker connected), does the signal on the output FETs change from the signal that you posted to a normal square wave?
calebjoshito:
Start a new thread and post your questions there.
Does the amp make the high frequency noise with no RCAs plugged in?
When you drive the amp to a moderate level (with a speaker connected), does the signal on the output FETs change from the signal that you posted to a normal square wave?
calebjoshito:
Start a new thread and post your questions there.
If it does it with that resistor out of the circuit, the problem is within the servo/feedback loop.
Is the voltage feeding the 5532 clean (free of ripple)?
As of now, the amp will go into protect (LED238 goes off) when driven to clipping (even without speakers) and has a high frequency noise (~50mv at the speaker terminals. Is this correct?
What's the DC voltage on pins 2 and 3 of the LM311 near the outputs (black lead on pin 4 of the IC for reference)? If the reference voltage on pin 3 is too low, it may be causing the protection circuit to trigger prematurely.
Is the voltage feeding the 5532 clean (free of ripple)?
As of now, the amp will go into protect (LED238 goes off) when driven to clipping (even without speakers) and has a high frequency noise (~50mv at the speaker terminals. Is this correct?
What's the DC voltage on pins 2 and 3 of the LM311 near the outputs (black lead on pin 4 of the IC for reference)? If the reference voltage on pin 3 is too low, it may be causing the protection circuit to trigger prematurely.
How do the waveforms on your amp compare to the ones in the following file?
http://www.bcae1.com/temp/mtx81000dwaveforms01.swf
http://www.bcae1.com/temp/mtx81000dwaveforms01.swf
Waveforms are almost same. Except the ones that have pulses (5), all pulses are bit lover (bit less voltage) and bit wider (last a bit longer).
Maybe when I tried to measure the voltage from yellow transformer the magnetic field screw up the measurement.
Even near the ic the scope sees about 6Vpp from air. 100mV ripple that I measured could be caused by that too.
Maybe when I tried to measure the voltage from yellow transformer the magnetic field screw up the measurement.
Even near the ic the scope sees about 6Vpp from air. 100mV ripple that I measured could be caused by that too.
The wider pulse width is required at the lower input voltage to reach the target voltage.
I think you need to determine why you're not getting consistent measurements. Do you have a ground clip to connect to the end of your scope probe? If so, you should use it (particularly when measuring the noise on the output).
Have you checked the continuity between the ground at the end of your probe and the chassis ground of the scope?
If the over-current protection circuit is tripping when you drive the amp to clipping and all output FETs, gate resistors and the diodes in the drive circuit are OK, I think you need to increase the value of the large resistors a bit more to increase the dead time. I can't think of anything else that would cause the amp's over-current protection to engage (LED238 going off).
It may be possible that the frequency of oscillation is too high or too low but I don't know how you'd change that. Maybe Eva could help if that's a problem with your amp. In the amps I've checked, the frequency of oscillation is between 60kHz and 160kHz. It varies and is at the lowest frequencies at high power output.
I think you need to determine why you're not getting consistent measurements. Do you have a ground clip to connect to the end of your scope probe? If so, you should use it (particularly when measuring the noise on the output).
Have you checked the continuity between the ground at the end of your probe and the chassis ground of the scope?
If the over-current protection circuit is tripping when you drive the amp to clipping and all output FETs, gate resistors and the diodes in the drive circuit are OK, I think you need to increase the value of the large resistors a bit more to increase the dead time. I can't think of anything else that would cause the amp's over-current protection to engage (LED238 going off).
It may be possible that the frequency of oscillation is too high or too low but I don't know how you'd change that. Maybe Eva could help if that's a problem with your amp. In the amps I've checked, the frequency of oscillation is between 60kHz and 160kHz. It varies and is at the lowest frequencies at high power output.
Perry Babin said:
You're right.Propes ground is actually damaged inside! I dont have ground clip, skope is grounded to power ground.
Perry Babin said:
I already did try increasing the resistors up to 470ohm. And it goes into protection way before clipping.
Perry Babin said:
Oscillation frequency is about right.
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