jl audio 1000.1 amp prblem

[ampjunkielikeme]

my baby has layed down on me....

my cd players rca jacks stopped working and took my amp with it.... help perry, im bassless

anyways....it powers up fine. no protection...idles at 1.5volts...
you can hook a speaker up to it and no weird noises or anything.

but if i hook my new radio rca jacks up, the amp just humms out of the speaker.....i can unhook the rca jacks , and touch the input rca jacks on the amp and it makes the same humming noise...

testing for dc voltage with the black probe on the chassis ground. red probe on the positive speaker wire, i get 57.84v dc

testing for dc voltage with the black probe on the chassis ground. red probe on the neg speaker wire, i get 57.90v dc

 

[Perry Babin]

Have you checked the shield ground on the head unit's RCA output jacks?

Check for DC voltage on the RCA shield of the amp. There shouldn't be any significant voltage.

 

[ampjunkielikeme]

i went ahead and got another cd player to replace the non working alpine..it needed to be replaced a while ago. i wished i would have done it sooner now.....
i picked up a kenwood kdc ps909 , no speaker wires, just 3 sets of rca jacks......kinda old , but it works great...lol


the jl amp does the humming thing with the newer cd player hooked up to it...but this kenwood is good. i can hook up another amp to it , and it has good audio....

 

[Perry Babin]

I think you still need to check both.

 

[ampjunkielikeme]

i dont have the alpine in front of me right now, it gave it to a buddy who said he could fix it....i just didnt want to bother with it...amps are my thing...lol

but the kenwood has no dc voltage on the rca jacks. all 3 sets..reads -0.001 v
ac voltage fluctuates from 0.00v to 0.98v ...thats with a low volume on the cd player ..

 

[ampjunkielikeme]

the alpine is history....i tried to get it back from my friend , but he took it and junked it out for parts......

would the 2 op amps right near the rca jacks keep the sound from being amplified?

 

[Perry Babin]

It's very strange that the power supply is producing rail voltage and it produces a hum when you touch the RCA jacks. This really seems like a signal source problem.

It's unlikely that the op-amps have failed. If you're 100% sure that the signal source isn't the problem, you could start troubleshooting by confirming that you have ±15v on pins 4 and 8 of the op-amps.

 

[ampjunkielikeme]

one rca jack will humm a little louder than the other one when you touch it.. does the same thing when you plug each rca up to the amp..

readings from the op amps right near the rca jacks
opamp 1 u-50
pin 4 -14.21v dc
pin 8 14.20v dc

opamp 2 u-51
pin 4 -14.21v dc
pin 8 14.22v dc

An externally hosted image should be here but it was not working when we last tested it.

are the other 3 ic's on the left side of the pic (u1,u2,u3) opamps to?

 

[ampjunkielikeme]

ok, i turned the low pass filter off, and turned the gain up a little , and i can hear some voices coming out of my sub now, but it still has that awful humming noise ....

 

[Perry Babin]

You checked the DC on the Kenwood head unit. You were supposed to check the continuity between the shield and ground. Is that 0 ohms?

You gave an AC voltage. Where was that read from (black and red probe placement)?

Yes. The other op-amps are likely NJM072s.

 

[ampjunkielikeme]

meter on ohms
kenwood cd player
black probe on the battery ground . red probe on the shield of the rca's i read 0.897m ohms

black probe on the cd players metal body. red probe on the rca shield. 2.2 ohms

do i need to switch my meter to continuity check and give you the readings?

yes, the ac reading were from the red probe on the center of the rca. and the black probe on the shield...

 

[Perry Babin]

What did you use as the 'battery ground'?

0.897m ohms = 897K ohms?

The shields are connected to the case of the head unit. The case of the head unit should be connected to chassis ground (~0 ohms).

 

[ampjunkielikeme]

the "battery ground" is what the cd players power ground is hooked to..

i do not get any continuity from the battery ground to the rca sheild..so it is doing what it is supposed to do..

yes, with my meter on ohms , i get that 0.897 m ohms

 

[Perry Babin]

Something isn't right. The case of the head unit should be connected to the battery ground. Since the shields are connected to the case of the head unit, you should find the same continuity from the shields to the battery ground. The amp grounds should have a bit of isolation from chassis (battery) ground but the head unit shields are almost always connected directly to chassis ground.

 

[ampjunkielikeme]

ok,,,i feel really dumb...

my kenwood cd player is setting on my table, the other rca jacks behind it somehow got pressed up against the wall, and was grounding out or something , so all i did was pull the radio closer to me and the amp stopped humming.....and the amp sounds great now....????????...i dont have a clue.....i have to go recheck all my wires or something...lol.....
and i gave my cd player away already..:crap:

 

[ampjunkielikeme]

hey perry, on another note...lmao

will a irf3205 be a good replacement for a irfz44v ? i just want to make sure.....thanks

 

[Perry Babin]

Not generally. Amps that use the Z44 typically have 100 ohm gate resistors. The 3205s typically need lower value gate resistors. What amp is it in?

 

[ampjunkielikeme]

ive got a kicker 850.2 that the irfz44v are in. they are all fried....

i think my sub is blown. i dont get a ohms reading on the voice coils when i tested it.....

 

[ampjunkielikeme]

ive got a kicker 850.2 that the irfz44v are in. they are all fried....

i think my sub is blown. i dont get a ohms reading on the voice coils when i tested it.....

 

[Perry Babin]

That amp uses 100 ohm gate resistors. I'm not sure what they use in the drive circuit so I don't know if it's going to be reliable if you only replace the gate resistors and use the 3205s.

Can you trace the circuit back to see which transistors they use between Pins 9/10 and the gate resistors?