Got this amp, the owner reversed polarity. There is no protection against this.
Now the amp is switching on, only when Battery is connected. No remote is connected. Starts producing rail, but no audio.
I changed allready one transistor and a resistor in front of the tl494, which was damaged. But now i stuck.
Any suggestions?
Now the amp is switching on, only when Battery is connected. No remote is connected. Starts producing rail, but no audio.
I changed allready one transistor and a resistor in front of the tl494, which was damaged. But now i stuck.
Any suggestions?
Attachments
Pin 12 of tl494 is connected to collector of mmbta 56. Pin 11 is connected to emitter of mmbta 56. On Base i have +12V. The transistor is open and the tl starts work. If i connect - on the base of mmbta56, the amp starts producing audio and the mmbta start burning.
Without the transistor inside, i have 6.2V + on Base.
With new transistor inside, if i lift the es1g, which is connected to the ps fet and pin 11 of the tl494, the amp stays of. But also not possible to start with remote...
Without the transistor inside, i have 6.2V + on Base.
With new transistor inside, if i lift the es1g, which is connected to the ps fet and pin 11 of the tl494, the amp stays of. But also not possible to start with remote...
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Probably the remote, not only enables the tl494, but also manages the muting circuit.
In this way, if now the amplifier turns on and produces rail, not having connected the remote, the muting circuit does not come out and therefore the amplifier does not produce any sound.
Try to ignore the fact that the amplifier turns on without remote, applies the same 12v on the remote and see what happens.
When the amplifier turns on by itself without remote, there is probably a pair of NPN and PNP transistors, one of which does not work well and remains active even without the remote command.
Unfortunately I don't have the schematic and therefore I can't help you in a precise way, but the principle of operation is surely this.
In this way, if now the amplifier turns on and produces rail, not having connected the remote, the muting circuit does not come out and therefore the amplifier does not produce any sound.
Try to ignore the fact that the amplifier turns on without remote, applies the same 12v on the remote and see what happens.
When the amplifier turns on by itself without remote, there is probably a pair of NPN and PNP transistors, one of which does not work well and remains active even without the remote command.
Unfortunately I don't have the schematic and therefore I can't help you in a precise way, but the principle of operation is surely this.
Attachments
with remote connected, there is still no audio. I think, that there is a ground resistor broken. But difficult to find.
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