Hello,
Got amp with blown output transistor. Replaced output transistors and powered up, it powered up fine, when i tried to feed signal in amp - it went straight in protection. After testing i saw that i dont have +15V on opamps and also +20V from the regulators.
Had blown FU701 - 0.375 fuse next to the regulators, replaced the fuse, but amp now is triggering my 10amp power supply when it tries to power up, i am afraid connect to 40amp supply.
What could it be? TDA7570 blown? When its cycling in/out, i can confirm that i have +/-20V and +/-15V.
Got amp with blown output transistor. Replaced output transistors and powered up, it powered up fine, when i tried to feed signal in amp - it went straight in protection. After testing i saw that i dont have +15V on opamps and also +20V from the regulators.
Had blown FU701 - 0.375 fuse next to the regulators, replaced the fuse, but amp now is triggering my 10amp power supply when it tries to power up, i am afraid connect to 40amp supply.
What could it be? TDA7570 blown? When its cycling in/out, i can confirm that i have +/-20V and +/-15V.
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You stated that it powered up fine. Does that mean that you have rail-rail oscillation on the output transistors if you don't drive a signal into it?
I didnt check the oscillation before replacing the fuse. With "powered up fine" i mean, that amp power up without going in protection. I should write more clearly.
I can remove the fuse, so the amp stops triggering my supply and can check oscillation on the output transistors, but i will lost +20V and +15V.
I will gonna see the oscillation if TDA7570 will not have +20V?
I can remove the fuse, so the amp stops triggering my supply and can check oscillation on the output transistors, but i will lost +20V and +15V.
I will gonna see the oscillation if TDA7570 will not have +20V?
Do you have a current limiter that would allow it to attempt to power up for a few seconds so that you could see which transistors are heating up?
I tried 55W car light bulb in B+ line, the bulb was flashing and amp was cycling in/out.
I left amp 10minutes and i didn't managed to see which transistor was heating up, also TDA7570 wasn't even warm.
All transistors was clamped to the heat sink.
I left amp 10minutes and i didn't managed to see which transistor was heating up, also TDA7570 wasn't even warm.
All transistors was clamped to the heat sink.
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When it was cycling, was the power supply drive switching off or did the supply stay on and the output stage was cycling on and off?
Scoped - the power supply drive signal is switching off.
Also i saw the PCB other side of TDA7570 is a bit discolored, nothing much, but there is sign of heat stress.
Also i saw the PCB other side of TDA7570 is a bit discolored, nothing much, but there is sign of heat stress.
You're going to have to defeat the protection circuit and power it through the limiter so it will stay on and you can troubleshoot it.
Soldering a bridge between the collector and emitter of Q602 and Q603 should keep the power supply on.
Remember that you must have a current limiter inline.
Remember that you must have a current limiter inline.
Tried, the PS drive signal keeps cycling on and off.
The PS stays on only, when one of the +/-15 and +/-20V regulator fuses (FU701,FU702) are discconected.
I tried to check voltages, when one of the regulator fuses were off the PCB and power supply wasnt cycling on/off. For the output fets i got strange voltages, IRF9640 gate and source got +84v, but IRF640 gate and source go -84v. I hope that i remember correctly the voltage polarity when i did measure it. 84vdc to the gates, could be right? Or its only because the TDA7570 dont have supply voltage?
The PS stays on only, when one of the +/-15 and +/-20V regulator fuses (FU701,FU702) are discconected.
I tried to check voltages, when one of the regulator fuses were off the PCB and power supply wasnt cycling on/off. For the output fets i got strange voltages, IRF9640 gate and source got +84v, but IRF640 gate and source go -84v. I hope that i remember correctly the voltage polarity when i did measure it. 84vdc to the gates, could be right? Or its only because the TDA7570 dont have supply voltage?
I am starting to think, is there point to remove TDA7570 from the board and check if the power supply stays on and not drawing excessive current?
What pins on the 494 are pulsing to make it go on and off?
Removing the outputs would be easier than removing the7570 IC and would allow you to troubleshoot the 7570 IC.
I think it would be best to find a way to keep te supply on and power it up through a limiter.
Removing the outputs would be easier than removing the7570 IC and would allow you to troubleshoot the 7570 IC.
I think it would be best to find a way to keep te supply on and power it up through a limiter.
Ok, maybe i had a bad solder bridge between legs, soldered new bridges using wires. Powered up via light bulb, now amp power supply stays on but it draws current - light bulb shines, have good drive signal on power supply fet gates.
The only i can see for now, that 7570 is slowly getting warm, all other transistors are clamped to heatsink.
The only i can see for now, that 7570 is slowly getting warm, all other transistors are clamped to heatsink.
output gonna be drive signal to the output fet gates?
No dc on the speaker terminals.
Tried to feed signal in amp - the 100hz sine wave on speaker output was like sawtooth wave.
No dc on the speaker terminals.
Tried to feed signal in amp - the 100hz sine wave on speaker output was like sawtooth wave.
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