Working on a RD Audio D9 generic half bridge amp. Amp had the power supply burned up. Nothing wrong in the output. No outputs shorted. Driver board appeared to be fine. Rebuilt the power supply and powered up the amp. Amp powers up and runs fine. Nothing heating up. But no audio on the output. I have audio to the driver board. Good square wave on the feed back pin of the driver board. Good drive to the outputs. Just not audio. Mute transistor checks good. I have drive to pin 1 of all the driver chips on the driver board. I installed a new driver board just to make sure it wasn't the problem. Strange to me. Any ideas what to check?
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Is there any modulation of the square wave?
What is the frequency of the square wave?
What's the DC voltage on pin 2 of the driver ICs with the black probe on the negative rail/shunt resistors?
What is the frequency of the square wave?
What's the DC voltage on pin 2 of the driver ICs with the black probe on the negative rail/shunt resistors?
I am getting the slight high frequency in the output that's common to these amps.When I was searching I read a post about that.
When you checked for signal getting to the driver board, did you check on the driver board header or farther back in the circuit?
I checked it on input side of R187. Sine wave that changed with frequency and amplitude of my input signal.. Small square wave in the output side of R187 and on the header pin of the driver board. About 400kHz.
It sounds like the circuit is working. The nulling of the input signal is what it's supposed to do at the input pin of the driver board.
When driving a strong signal into the amp, are you seeing a perfectly stable, clean, sharp square wave, swinging rail to rail at the input of the output filter inductors?
When driving a strong signal into the amp, are you seeing a perfectly stable, clean, sharp square wave, swinging rail to rail at the input of the output filter inductors?
Did you check to see if all the regulated voltages are present ?
The + -15 volts , positive 12 volts on both regulators, and the + - 5 volts
Also did you lift and check all 47uh inductors ?
Just a thought since I just rebuilt one of these amps and have one more to go
The + -15 volts , positive 12 volts on both regulators, and the + - 5 volts
Also did you lift and check all 47uh inductors ?
Just a thought since I just rebuilt one of these amps and have one more to go
Hi Caraudioguy, Yes Checked +/- 15 volts. Have it to all the TL074s. 12 volt is present on both transistors. I have 12 volts on the header pins of the driver board. I have +/-5 volts on the header pins of the driver board.
I'm assuming you're talking about the output inductors. I didn't lift one side and test them. They are running warm and I do see the noise on the output on my scope. Just no audio. If they were open I wouldn't see that and I assume if one was shorted I would be taking out outputs right? Thanks
I'm assuming you're talking about the output inductors. I didn't lift one side and test them. They are running warm and I do see the noise on the output on my scope. Just no audio. If they were open I wouldn't see that and I assume if one was shorted I would be taking out outputs right? Thanks
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"When driving a strong signal into the amp, are you seeing a perfectly stable, clean, sharp square wave, swinging rail to rail at the input of the output filter inductors?"
Yes Perry. perfectly stable, clean, sharp square wave. Swinging rail to rail. 235 volts peak to peak.
Yes Perry. perfectly stable, clean, sharp square wave. Swinging rail to rail. 235 volts peak to peak.
If you lift then off board they should read 5 ohms . If you do not get a reading they are defective .
Perry wrote, "I think you'll have to disable the 21844s to troubleshoot the problem"
How would disabling the 21844s help me? BTW, the driver board is new. How would I go about disabling them and would I have to pull the outputs to prevent them from possibly shorting? Thanks.
How would disabling the 21844s help me? BTW, the driver board is new. How would I go about disabling them and would I have to pull the outputs to prevent them from possibly shorting? Thanks.