Alright, so I have this JL 500/1, and I just put in a new 8w7 and hooked it all up and it was pretty quiet, it sounded clean and clear, just quiet. So I went to adjust the input sensitivity as described by the manual.
So I get it all setup, and even with the gain all the way clockwise, while running a 50hz sine wave at 0db, I am still only getting around 5.5v on the sub output terminals. It's supposed to be up to 38.7v for a 3 ohm sub.
I'm using an Alpine CDE-126BT headunit, with all EQ's off. Subwoofer out is on with it turned up 3/4 of the way.
Voltmeter was set to AC.
Amp Settings:
Infrasonic Filter: Off
Bass EQ: Off
Low Pass filter: 24db ; knob at 85 ----Also tried with this off.
Input Voltage: Low
So I get it all setup, and even with the gain all the way clockwise, while running a 50hz sine wave at 0db, I am still only getting around 5.5v on the sub output terminals. It's supposed to be up to 38.7v for a 3 ohm sub.
I'm using an Alpine CDE-126BT headunit, with all EQ's off. Subwoofer out is on with it turned up 3/4 of the way.
Voltmeter was set to AC.
Amp Settings:
Infrasonic Filter: Off
Bass EQ: Off
Low Pass filter: 24db ; knob at 85 ----Also tried with this off.
Input Voltage: Low
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Measure the AC voltage on the RCAs feeding the amp. Place the black probe on the RCA shield and the red probe on the center conductor. Do this with the 50Hz sine wave and the volume set to ~80%.
Hmmm, doing this test I only get about 86mV from eeach RCA. This is with the 50hz sine wave playing with volume at 30 out of 35. That doesn't seem right.... this is pretty much a brand new headunit though.
Measure the resistance from the shield ground on the head unit to the case of the head unit (no RCAs plugged in).
RCA Shield Repair
RCA Shield Repair
Does it matter if the head unit is on or off, and which lead goes to which point?
Here is what I found:
Head unit off; red lead on case/black on RCA shield = .6 ohm
Head unit off; red lead on RCA shield/black on case = 0 ohm
Head unit on; red lead on case/black on RCA shield = 0 ohm
Head unit on; red lead on RCA shield/black on case = 2.6 ohm
Probably made that way more complicated than necessary, but thought I'd share the results... thanks
Here is what I found:
Head unit off; red lead on case/black on RCA shield = .6 ohm
Head unit off; red lead on RCA shield/black on case = 0 ohm
Head unit on; red lead on case/black on RCA shield = 0 ohm
Head unit on; red lead on RCA shield/black on case = 2.6 ohm
Probably made that way more complicated than necessary, but thought I'd share the results... thanks
You should not read anything different no matter the probe orientation or the head unit on of off. Did you disconnect the RCA cables from the head unit?
It's probably not important.
Go back and measure the AC voltage on all of the RCA outputs.
It's probably not important.
Go back and measure the AC voltage on all of the RCA outputs.
Yes I had them disconnected. Maybe a problem with my dmm? It was definitely reading differently.
Measure the AC voltage on RCA's on the head unit itself with the sine wave playing? Thank you for your help so far, I appreciate it!
Doing this, I get 137.5mV for the front RCA outs, and 97mV for the Subwoofer RCA outs.
This is with the same volume and tone that was previously measured.
This is with the same volume and tone that was previously measured.
It appears that the head unit is not working properly. Do you have a different head unit that you could try this with?
If you're sure that you're doing every test properly and that your meter is working properly, you should return it to have it checked out.
I'm assuming that you know how to use the head unit and there are no hidden items buried in a menu somewhere that's causing the output to be low. Are you sure that there is no muting function that's engaged?
I'm assuming that you know how to use the head unit and there are no hidden items buried in a menu somewhere that's causing the output to be low. Are you sure that there is no muting function that's engaged?
I will go triple check the settings, but as far as I could gather there were no settings that would do this. I will report back shortly.
I still see no settings that are out of place. I have read through the head unit manual to double check, and have checked all settings on the head unit. If a setting is the problem, I cannot find it. Thank you again Perry.
When you get it back or get a replacement, measure the AC voltage on the RCA outputs before you connect the RCAs to the head unit. If the head unit works properly at first and not after you connect it to the amp, you'll know that the amp may have a problem. It's unlikely since the most common problem causes the shields to open (and yours don't appear open) but at least you'll know.
Well, after testing the head unit at the audio shop I have realized that I'm a dumby and made an error reading voltage and the head unit is in fact fine. I was using my ipod to run the 50 hz test and didn't have the volume on the ipod itself maxed out. The sub outs are actually seeing 3v+, and it is making it to the amp fine.
However I am now getting zero output on the amp, which leads me to believe there is something wrong with the amp itself. Perry, do you work on these amps, I have a feeling repairing it will be over my head. Or should I just look into replacing it outright?
Sorry for my mistakes and thanks again for helping me so much.
However I am now getting zero output on the amp, which leads me to believe there is something wrong with the amp itself. Perry, do you work on these amps, I have a feeling repairing it will be over my head. Or should I just look into replacing it outright?
Sorry for my mistakes and thanks again for helping me so much.
I work on them but I have a backlog of work I need to clear before I accept any more work.
When you power up the amp, what is the DC voltage on the positive and negative speaker terminals (black probe on amp ground).
When you power up the amp, what is the DC voltage on the positive and negative speaker terminals (black probe on amp ground).
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