Question about Legacy Audio LA720 Car Audio Amplifier
Ok i'm having a little problem with this amplifier. it started when a ground wire that travels from the chasis of the amplifier to the PCB came off the PCB and shorted 4 IRFZ46 transistors causing those 4 transistors to smoke. so i have replaced those transistors and have also replaced 5 2200uF 25v Capacitors in this unit as the tops were bulged. now the unit powers up as the power LED lights up. now here's where the fun begins, if i leave the Amplifier in Stereo mode i can't get any sound through the unit and the protection light comes on. now if i bridge the unit and go to Mono the protection light shuts off, but still get no audio through it(exept for a loud hum) and this happens on all 4 channels. if you can think of anything that would help my cause it would be greatly appreciated.
I would first check for "rail votage" at the rectifiers... If all of your audio transistors are not getting around 40 volts then check the transistors you replaced. They should be getting a 5 volt (10 volt square wave is checked with a scope) "drive" signal. If half of your power supply transistors are not getting a drive signal then replace the kia494/tl494/kia594/tl594---whatever it is. thats the ic chip that supplies the "drive" signal to the power supply transistors. Also follow the board closely out of the power supply transistor to the 494 chip.. there should be some small driver transistors in between.. make sure they are not shorted or fried as well... let me knoe if you need more help
Posted on Aug 18, 2007
Tips for a great answer:
May 11, 2011 | Dual XPA2100 2/1 Channel 300 Watt...
Apr 24, 2011 | Sony XMGTX1852 Car Amp
Aug 05, 2010 | Clarion APX200.2M 2/1 CHANNEL POWER...
May 18, 2010 | Eclipse EA3422 Car Audio Amplifier
May 10, 2010 | Boss AUDIO SYSTEMS D13002 Car Audio...
Dec 11, 2009 | Sony Xplod XM-554ZR Car Audio Amplifier
Sep 22, 2008 | Rockford Fosgate Audio Players & Recorders
Mar 10, 2007 | Sony XM-2200GTX Car Audio Amplifier
Usually answered in minutes!
Step 2: Please assign your manual to a product: