JL Audio E4300, lights up, no sound

[807tubenut]

Just got around to testing it, the Bias setting's were set to 5mv per channel (tested @ the test header for each channel), The SMPS is producing stable voltage, and there are no dead output's.


anyone do a repair on one of these?

 

[Perry Babin]

Are all of the LEDs lit on each of the driver boards?

 

[807tubenut]

No driver boards in this amp, It looks nothing like my old 4/300's


This is the newest style JL E series

 

[Perry Babin]

OK. I'm not familiar with that one. Do you have audio anywhere in the amp?

Do ALL audio op-amps have both positive and negative regulated voltage on their power supply pins?

If there are any J111 or J108 transistors (typically used for muting) do they have -15v on their gate (leg 3)?

 

[807tubenut]

Ill be tracing audio through the circuit tomorrow, 1khz sine wave here we come!, it uses a front end like Iv never seen before, about 12 tsop-8 IC's (likely double op-amps), and the usual assortment of pull down,coupling,filter bits around them, I did not get time to make out there P/N#, but I bet we will find there double OP-amps, seeing as how I did locate the + and - 15v rails, they were in fantastic condition, I bench loaded them with an external load resistor, no issues at all, full voltage was realized from no load to load, so I think the supply is in good shape.



Ill grab the high res shots in the morning, and post them to amp guts!



Buckle up Perry, this might be 1 more JL bumpy ride!

 

[Perry Babin]

In other JL amps, they use two op-amps as buffers and another op-amp in differential mode for each input. This one probably uses the same configuration.

 

[807tubenut]

Do they have a history of going kaput when driven to max gain? the amp came to me with its gain knob maxed out, and IIRC the guys HU was a HV kenwood, in the range of about 8v peak, so the little op-amps got hammered daily till no more. strange they all went at once, he said all 4 channels went down at the same time.


How do you feel about the 5mv idle setting? i was thinking a tad cooler, around 2.5mv?

 

[Perry Babin]

The bias you set is probably not excessive. The average I've seen for amps that had not been serviced is about 4mv. If the amp runs hot at idle, you can set it lower. If you have to reduce it if you have to work on the amp without the sink.

I doubt the op-amps have failed. I was trying to help you understand why they would use so many op-amps.

It's likely a muting problem. Either the muting circuit is defective or the protection circuit is not allowing the amp to release the muting.

Are there any burned resistors?

 

[807tubenut]

-13.5 on the Gate of each J111 (pin 1 on these)

 

[Perry Babin]

The muting transistors aren't causing the loss of audio. The negative gate voltage has them driven off.

 

[807tubenut]

That is correct, but these were all shorted

Replaced all 4 of them, amp works, I have it on my load cells right now, idle bias got adjusted to 3mv, and the idle current is right at 1.5amps with music off.



Thanks Perry! Iv got more to fix this winter

 

[Perry Babin]

4 defective muting transistors? That's strange.

 

[807tubenut]

They all had the center pin burned out, only had to unsolder the outermost 2 pins.

 

[superjoey01]

hi you guys i have a JL Amp E1400D and it sound almost same problem where are those muting pins located so i can test them or repair them