Amplifier won’t turn off

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=85339
Printed Date: May 09, 2024 at 5:40 AM

Topic: Amplifier won’t turn off

Posted By: zero signal
Subject: Amplifier won’t turn off
Date Posted: November 08, 2006 at 1:59 PM

I have a Kenwood KAC-729S 600W which is giving me a hard time. As long as 12VDC is applied from the battery, the amp is on.... regardless of whether or not the switched 12VDC is available.

I broke out my Fluke meter and checked the switched 12VDC lead from my head unit, and verified that my vehicle wiring is in fact, good. It seems as though the "switched 12V" circuitry in my amp is faulty, causing my amp to remain on at all times. As a temporary fix, I have installed a kill switch on the 12VDC lead to keep the amp from draining my battery.

Has anyone else experienced this problem with an amplifier before? I really need a schematic to troubleshoot it down to component level, but have been unable to find one. I did take it apart, but found no visual indications (e.g. burned components, "hot spots" on the PWB, or damaged foil runs).

Replies:

Posted By: jonathancullen
Date Posted: November 08, 2006 at 2:09 PM

i had a sony deck where the same thing happend. try hooking your remote wire to you ignition and see if that fixes it. if all else fails you will just have to run it like it is, with a kill switch.

Posted By: killer sonata
Date Posted: November 08, 2006 at 3:10 PM

if the ground is bad the amp will turn on by itself

Posted By: zero signal
Date Posted: November 08, 2006 at 7:51 PM

killer sonata wrote:

if the ground is bad the amp will turn on by itself

I measured the resistance between the GND terminal on the amp, and the chassis itself. My meter read less than .2ohms.

Thanks for the advice though... I'll look for a better grounding point and see if that works.

Posted By: i am an idiot
Date Posted: November 08, 2006 at 7:59 PM

You have a shorted transistor on the turn on path. You can fix it without a schematic, just follow the remote trace and look for a small transistor in that path that is shorted, The remote trace goes from the connection on the outside of the amp to a 16 pin chip with the numbers 494 or 594 on it TL494 TL594 UPC494 UPC594 it goes to pin 12 of that chip

Posted By: zero signal
Date Posted: November 09, 2006 at 10:30 AM

I double-checked my ground. Less than .2ohms from the ground terminal on my amp to the chassis.

There are no IC chips in the remote 12VDC circuit. This amp uses the common tripod transistors. I'm currently researching the part numbers to see if I can find the specs on them. This afternoon I'm going to check them out with my meter. I'll reply back with my findings.

Thanks again!

Posted By: i am an idiot
Date Posted: November 09, 2006 at 8:51 PM

Trust me there is a 494, 594 IC controlling the power supply of your amp, Kenwood sometimes likes to put them off in left field way away from the rest of the supply.

Common Tripod transistors??????????????????