This amp is not passing audio. When I received it, the inputs were missing the insulators and were tightened down to the metal case grounding them out. Here is what I have on the 10 Pin connector with 14V on the B+.
1: 4.99V
2: -14.74V
3: 14.02V
4: 2.358V
5: 13.31V
6: 13.46V
7: .636V
8: 13.24V
9: 13.31V
10: 10.7mV
What do I check next?
1: 4.99V
2: -14.74V
3: 14.02V
4: 2.358V
5: 13.31V
6: 13.46V
7: .636V
8: 13.24V
9: 13.31V
10: 10.7mV
What do I check next?
Can you find audio on any of the output pins of any of the op-amps on the preamp board?
Have you tried lifting then re-seating the preamp board a few times?
Have you tried operating all switches and pots through their entire range with signal and a speaker to see if audio ever played through?
Have you tried lifting then re-seating the preamp board a few times?
Have you tried operating all switches and pots through their entire range with signal and a speaker to see if audio ever played through?
Those look OK so it may not be causing a problem but I'd suggest replacing it.
Does the amp produce absolutely no audio or does it produce a very low level output?
What is the DC voltage on the positive and negative speaker terminals (black probe on the amp ground)?
Do you have ±15v on the power supply pins of the op-amps just behind the input RCAs?
Does the amp produce absolutely no audio or does it produce a very low level output?
What is the DC voltage on the positive and negative speaker terminals (black probe on the amp ground)?
Do you have ±15v on the power supply pins of the op-amps just behind the input RCAs?
I'm not sure that it is 100% The original complaint was it has low output. I think it is still lower than it is supposed to be.
I just checked the RCA outputs from the CD player with scope, nice and clean. I have used it on several other JL 500's, it should be working with this one too without taking RCA shield to ground. If I don't ground the shield, it has lots of 60Hz hum.
I just checked the RCA outputs from the CD player with scope, nice and clean. I have used it on several other JL 500's, it should be working with this one too without taking RCA shield to ground. If I don't ground the shield, it has lots of 60Hz hum.
Try it with a standard head unit with its ground connected to the amp ground (as it normally would be). If it works like that, I return it to its owner. I know that some of the JL amps will not work properly unless the shield of the source is grounded.
There are multiple versions, there may have been changes in the input circuit.
Was your MP3 player connected to a charger or was it running from battery power?
There are multiple versions, there may have been changes in the input circuit.
Was your MP3 player connected to a charger or was it running from battery power?
I'm looking at this amp again.
I installed another LM324 at U400 but, I still only have ~2.265V across that 5.6V Zener near the U400.
With the crossover off and I drive a 1V, 100Hz signal into the RCA inputs, I can only get between ~35.9VAC at minimum gain and ~40.1VAC at maximum gain setting measured across the output terminals. Increasing the signal to 2V has no impact at the output terminals.
I suspect there are still problems on the preamp board. Any sugggestions on what to check out next?
I installed another LM324 at U400 but, I still only have ~2.265V across that 5.6V Zener near the U400.
With the crossover off and I drive a 1V, 100Hz signal into the RCA inputs, I can only get between ~35.9VAC at minimum gain and ~40.1VAC at maximum gain setting measured across the output terminals. Increasing the signal to 2V has no impact at the output terminals.
I suspect there are still problems on the preamp board. Any sugggestions on what to check out next?
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