HI,
I am done with the Pioneer amp. This morning a friend brought this Onkyo amp and ask me to fix it. This is an AV surround amp using a surround processor and a micro controller. I am unable to get the schematic for this amp. The power amp is an analog circuit, which I am familiar with but the rest is digital I guess, which I am not familiar with, but my friend insisted me to give a try. The amp was totally dead including the "standby LED". Upon checking, the standby transformer was blown, two (0.22 ohms) emmiter resistors and 3 power transistors were also blown. After replacing them, I turned ON the power switch and the standby LED comes ON, upon pressing the standby switch, the display comes on and after 2 secs, the front speaker relay turns ON. The speakers were connected but no signal plugged in. I left the amp ON for more than a minute. I realise that the power amp is active and connected because I hear slight click sounds when I turn the volume pot up and down. I OFF the amp connected a CD player to the CD input and turn ON the amp again. The amp came ON,the relay clicked on, the Display shows DVD. Now I pressed the CD button, and instantly the relay clicked OFF , Display went OFF and the standby LED was flicking. I turned OFF the power switch, disconnected the CD input and turned ON the amp again. The amp came back again and the relay ON again. The display shows CD. Now with the amp ON, I connected the input to DVD. The amp still ON. Now since the input is connected to DVD, I pressed the DVD selector button. Again instantly the amp went OFF. I noticed that, when there is no connected Input to the amp, the amp seems OK. When an input signal enters the circuit, it cuts OFF.
I hope someone experienced with AV amps and digital circuits can give me some guidance.
Thanks
Carlos
I am done with the Pioneer amp. This morning a friend brought this Onkyo amp and ask me to fix it. This is an AV surround amp using a surround processor and a micro controller. I am unable to get the schematic for this amp. The power amp is an analog circuit, which I am familiar with but the rest is digital I guess, which I am not familiar with, but my friend insisted me to give a try. The amp was totally dead including the "standby LED". Upon checking, the standby transformer was blown, two (0.22 ohms) emmiter resistors and 3 power transistors were also blown. After replacing them, I turned ON the power switch and the standby LED comes ON, upon pressing the standby switch, the display comes on and after 2 secs, the front speaker relay turns ON. The speakers were connected but no signal plugged in. I left the amp ON for more than a minute. I realise that the power amp is active and connected because I hear slight click sounds when I turn the volume pot up and down. I OFF the amp connected a CD player to the CD input and turn ON the amp again. The amp came ON,the relay clicked on, the Display shows DVD. Now I pressed the CD button, and instantly the relay clicked OFF , Display went OFF and the standby LED was flicking. I turned OFF the power switch, disconnected the CD input and turned ON the amp again. The amp came back again and the relay ON again. The display shows CD. Now with the amp ON, I connected the input to DVD. The amp still ON. Now since the input is connected to DVD, I pressed the DVD selector button. Again instantly the amp went OFF. I noticed that, when there is no connected Input to the amp, the amp seems OK. When an input signal enters the circuit, it cuts OFF.
I hope someone experienced with AV amps and digital circuits can give me some guidance.
Thanks
Carlos
Did you use the correct components and set the bias to avoid damage somewhere else on the amp?
The manual is under TX-SV373.
The manual is under TX-SV373.
I replaced the standby transformer with a 9V ac transformer. The 3 power transistors I replaced were One 2SC5197 and Two 2SA1940 and 2 (0.22 ohms3 watt) resistors , as what were in the amp. I do not know whether the other components and bias were set correct as the schematic was not in hand. I will check with the TX-SV373 schematic. I noticed that someone has meddled with the circuit earlier because the power transitors pins have been unsoldered from the board. I also noticed that most of the other transistors on the power amp board have been removed and resoldered back again.
Thanks
Carlos
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