Ok. Today I’m having trouble with a Power Acoustiks OV2-1600 Gothic Series amplifier. It’s a huge amp with lots of unused real estate. Should be simple, right?
The amp powers up and plays fine in the right channel but the left channel is weak and staticky sounding. The amp uses 3 A1694 mosfets and 3 C4467 mosfets in each channel. In the channel that sounds weak and staticky the C4467s heat up pretty rapidly. The amp is sitting into the heatsink but the mosfets are not clamped to the heatsink.
The individual components test good but I’m not sure what is happening to cause the weak amplification and heat. Any ideas?
I am attaching photo of the affected area.
The amp powers up and plays fine in the right channel but the left channel is weak and staticky sounding. The amp uses 3 A1694 mosfets and 3 C4467 mosfets in each channel. In the channel that sounds weak and staticky the C4467s heat up pretty rapidly. The amp is sitting into the heatsink but the mosfets are not clamped to the heatsink.
The individual components test good but I’m not sure what is happening to cause the weak amplification and heat. Any ideas?
I am attaching photo of the affected area.
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I did find a cracked solder joint on one of the rectifiers on the left channel the center leg solder joint is questionable to say the least. Maybe that is part of the problem. I’m going to wick this solder out and re-solder this leg right now. This IS one weak feeling board to say the least. I bet this thing vibrates like crazy.
David
David
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Ok. That eliminated the over heating problem but the left channel is still weaker than the right channel. Static is gone too by the way.
David
David
I did clean them with Deoxit and worked them back and forth with no progress. I decided to pull then preamp board and flipped it over to examine the solder joints. I see a lot of corrosion on there. I’m going to clean this board up and see if anything is going on underneath all this white corrosion.
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How much weaker?
Drive a low frequency sine wave into both then measure the output voltage.
Is it weaker at all switch and potentiometer settings?
Drive a low frequency sine wave into both then measure the output voltage.
Is it weaker at all switch and potentiometer settings?
Hi Perry. I will do that when I get this cleaned up and put back together. Just listening to it before it was about 75 percent weaker than the right channel. (Just an estimate). The volume on the weak channel would go up and down with the gain pot and the frequency would change with the crossover pot.
David
David
Ok Perry. I took some measurements as requested.
I’m getting 48.2 volts rms on the right channel and 10.7 volts rms on the left channel at the speaker terminals.
I am getting plus and minus 47 to 48 volts at the rails feeding the output mosfets on both channels.
David
I’m getting 48.2 volts rms on the right channel and 10.7 volts rms on the left channel at the speaker terminals.
I am getting plus and minus 47 to 48 volts at the rails feeding the output mosfets on both channels.
David
At any point on the settings for any of the controls, do the signals become approximately the same?
No. There is never anything close to a match up.
With gain all the way down I’m getting 6.5 volts rms and 2.8 volts rms on the right and left channels. I’m feeding a pretty strong signal in. 80 hertz -12db.
David
With gain all the way down I’m getting 6.5 volts rms and 2.8 volts rms on the right and left channels. I’m feeding a pretty strong signal in. 80 hertz -12db.
David
With bass boost off.
I get 5 volts rms and 3.5 volts rms with gain all the way down. With gain all the way up I get 18.64 volts rms and 7.7 volts rms. With gain at 50 percent I get 9.4 volts rms and 4.9 volts rms.
David
I get 5 volts rms and 3.5 volts rms with gain all the way down. With gain all the way up I get 18.64 volts rms and 7.7 volts rms. With gain at 50 percent I get 9.4 volts rms and 4.9 volts rms.
David
With the crossover in full range mode and bass boost off and gain at 50 percent I get 10.3 volts rms and 5.2 volts rms. With gain at zero I get 5.4 volts and 3.7 volts rms. With gain 100 percent I get 21.9 volts and 4.7 volts rms.
David
David
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Can you follow/read a schematic?
I have the diagram if you want that. If you can't read the diagram, I can help you troubleshoot.
I have the diagram if you want that. If you can't read the diagram, I can help you troubleshoot.
http://www.bcae1.com/temp/poweracoustik - OV_SCH.pdf
I'd work back from the input to the differential stage if each channel. If the signal is different there, work back toward the preamp section. If the signals are even there, the problem is likely in the gain of the output stage.
I'd work back from the input to the differential stage if each channel. If the signal is different there, work back toward the preamp section. If the signals are even there, the problem is likely in the gain of the output stage.
Okay. Turns out that the problem was bad electrolytic caps in the signal processing path. I found four bad caps but I decided to replace all of the electrolytic caps in the signal processing circuit. Total of 12 caps. Cheap insurance to make it doesn’t come back with same problem a few months later.
I replaced these in the middle. One was leaking a little.
David
I replaced these in the middle. One was leaking a little.
David
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