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Randy62 16th February 2012 02:38 AM

Help identify smd in Kicker KX 1200.1
I have been searching the web since last night and I cant find any thing.
I found out that I have no Vcc on the lm361.I have a different model Kicker 1200.1 that has the lm361 and it has 2.8 volts on pin 14 Vcc so I feel this is my problem.
The board has it marked as U15 so its leading me to believe its an IC or regulator.
Its an SOT-223 style with the # 3B on one end and 440 on the other.
Any help would be greatly appreciated.

Perry Babin 16th February 2012 02:57 AM

This IC operates from 5v. It's split to +2.8 and +2.2 (approximately) on the IC's power supply pins for the logic section of the IC.

Randy62 16th February 2012 04:27 AM

Wow,.Thank you.
That explains a lot.Do you have any idea what the part # is for a replacement.
What do you think about trying to make a voltage divider out of resistors or maybe zeners for testing .Ive been working on this thing for 2 days in my spare time.I have replaced a bunch of parts already.Q105 had a solder bridge and it looks like it sent high voltage into the outputs on the lm361.Q105 supplies the 2.8 volts to the lm361 Via the 3b440.I get 31 ohms on pins 2-3
of the 3b440 out of circuit.
I am also getting -9volts dc offset on input 1 with audio super imposed on it and a 80khz triangle wave on input 2 of the 361.I removed the 361 and replaced the tl072 and still I have the -9volts at input 1.
Any thoughts on any off this?

timwebb 16th February 2012 06:13 PM

Go to all data sheet and type lm361. So u have DC on the RCA shield? Exactly how much?

Perry Babin 16th February 2012 10:45 PM

If you shorted the outputs of the LM361, it's likely defective.

If you're going to replace it, you should use low temperature solder. The pads are fragile and will often delaminate if you use regular solder. The ones that completely come off of the board aren't connected to anything but it looks better if they're in place. ChipQuik is low temp solder that will help prevent damaging the board.

Randy62 17th February 2012 02:04 AM

Sorry.I was wrong about the transistor.Transistor 104 had the solder bridge and I think it sent about 70v into the outputs on the 361.Anyway I replaced the 361 and still had no output.Thats when I got out the other 1200.1 for a reference, it is a different circuit.Similar,but different.
Thats how I found out I was missing the 2.8v on pins 8,13,14 on the 361.and found -9vdc on pin3.
After I removed the 361 I was still missing the 2.8vdc so that led me to the 3b440 and I still had -9vdc on pin 3 so I replaced the tl072 that drives pin 3 and its still there.I have not tried to replace the 361 yet because of the Bad 3b440.
So Im kinda in limbo until I can get the 2.8vdc Thats Why I ask If there is any way to rig it with resistors or zeners or what part crosses to the 3b440.If I get that part of it going then I can try to tackle the dc offset problem on pin 3.
I have good +/- 65vdc rail voltage.Good +/-12vdc.
Good 80khz and audio at the 361 but no output.
The solder bridge was there when I got the amp.It looks heat related.I had to replace about a dozen smd resistors and 4 drivers.This amp belongs to a good friend of mine so I really hate to disappoint him but Ive got a LOT of other things waiting in line.
Thanks in advance.

Perry Babin 17th February 2012 06:15 AM


Randy62 17th February 2012 09:06 AM

Thank you.
Thats what I needed.
I wish I knew how you found that.
I will follow up on this when I get it.

Perry Babin 17th February 2012 09:10 AM

I know that it was a KIA431 but I knew that it wouldn't be available. I searched Octopart with the generic part number and case style.

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