The bias in one of the channel is not holding.After a few seconds the output start to over heat.I see about 1.567v pulsing on the output terminal .
I did not find anything bad in that channel.
Any suggestions?
I did not find anything bad in that channel.
Any suggestions?
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Does heating the bias transistor bring the current draw down when it starts to increase?
Is there a load on the amp when the current draw increases?
Is there a load on the amp when the current draw increases?
Do you have the same problem with the amp fully assembled (transistors tightly clamped to the heatsink, heatsink compound...)?
What work has been done to that channel?
What work has been done to that channel?
No work had been done on that channel.I removed a few transistors to test them.
Original problem is amp goes in protect so I by-pass the protection and realize that problem .
Original problem is amp goes in protect so I by-pass the protection and realize that problem .
Does the bias runaway with the outputs clamped down?
Have you tried swapping the bias transistors from one channel to the other to see if the problem follows that transistor?
Have you tried swapping the bias transistors from one channel to the other to see if the problem follows that transistor?
When clamp down it’s still behaving the same way.I installed another bias transistor same thing.
The dc offset on the output is what I think is putting the amp in protect in protect.
The dc offset on the output is what I think is putting the amp in protect in protect.
If you clamp the bias transistor down (temporarily), will it hold the bias?
Could it have a leaky driver transistor?
It's rare to have DC offset protection on the cheap amps but you could be right.
Are the emitter resistors within tolerance?
Could it have a leaky driver transistor?
It's rare to have DC offset protection on the cheap amps but you could be right.
Are the emitter resistors within tolerance?
It originally gets clamp down together with the outputs.I try two new drivers same.
Emitter resistors test ok.
I remember i had a similar problem years and you told me to increase or decrease the value of one of the transistor near the bias transistor but i
dont remember exactly.
Emitter resistors test ok.
I remember i had a similar problem years and you told me to increase or decrease the value of one of the transistor near the bias transistor but i
dont remember exactly.
That's sometimes an option when both/all channels are over/under biased. You would make the bias transistor conduct more to reduce idle current. That can generally be done by increasing the B-E value or decreasing the B-C value slightly.
There appears to be another problem, causing the DC offset.
Can you simply clamp the outputs and heat the bias transistor to see if the amp will produce clean audio rail to rail?
The 1.2v offset won't hurt a dummy load or a high-power woofer.
Knowing if the amp can produce clean rail-rail audio may help in troubleshooting.
There appears to be another problem, causing the DC offset.
Can you simply clamp the outputs and heat the bias transistor to see if the amp will produce clean audio rail to rail?
The 1.2v offset won't hurt a dummy load or a high-power woofer.
Knowing if the amp can produce clean rail-rail audio may help in troubleshooting.