JL Audio 250/1 HF no output - diyAudio
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Old 6th June 2008, 03:00 AM   #1
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Default JL Audio 250/1 HF no output

Hi All, I am still kind of new at the forum and appreciate all the help. I just started working on a JL Audio 250/1. It powers up fine current draw looks ok. Power light is on low ohm and thermal are out. Amp has about a 65khz sinewave on the output with no input. I think it might be something with the low filter but don't know how to check it.

Thanks in advance for all the help.
RJcrafts
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Old 6th June 2008, 06:12 AM   #2
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Location: Louisiana
What's the amplitude of the 65kHz signal with and without a speaker connected to the amp?

Does the current draw increase when you connect a speaker?

How much DC voltage do you have across the positive and negative speaker terminals (black meter probe on the negative speaker terminal, red meter probe on the positive speaker terminal)?

How much DC do you have from the chassis ground terminal to the positive speaker terminal (black meter probe on the chassis ground terminal, red meter probe on the positive speaker terminal)?

How much DC do you have from the chassis ground terminal to the negative speaker terminal (black meter probe on the chassis ground terminal, red meter probe on the negative speaker terminal)?
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Old 7th June 2008, 01:22 AM   #3
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Hi Perry, Thanks for the response. Here is what I have found,
1v p-p w load
0v p-p w/o load
current draw about same w and w/o load
0v across speaker output terminals
gnd to pos = 30.0 vdc
gnd to neg = 30.0 vdc

nice clean sine wave. I have looked closely all over the amp for and obvious component damage and ohmed out outputs, nothing appears shorted.

Any ideas on where to start troubleshooting this amp would be greatly appreciated.

Thanks
RJcrafts
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Old 7th June 2008, 04:43 AM   #4
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Join Date: Nov 2003
Location: Louisiana
I'm not sure that there is a problem. Although I would have expected the with/without load numbers to be reversed, everything looks OK. The signal won't be audible. Many class D amps have similar leakage through their output filters and it causes no problem. If the amp produces clean output when driving a speaker, it's probably in good working order.
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