Darlington transistors are more difficult to check because there are often internal resistors and diodes as well as two internal transistors. It's generally best to compare the transistor to another identical transistor when trying to determine if one is defective (when they're not simply shorted).
Ok, I have removed that one. Now under about a 2 watt load I am drawing about 5 amps.
There is one that has 14mv when the other have 7mv and another that has 13 mv when the others have 8mv. Should those be replaced?
Also, I have the bias set to just where it seems to remove crossover distortion at the 0V line at this wattage. It becomes pretty obvious when the bias is set to high as the current goes way up.
The FETs are not heating up at this point.
There is one that has 14mv when the other have 7mv and another that has 13 mv when the others have 8mv. Should those be replaced?
Also, I have the bias set to just where it seems to remove crossover distortion at the 0V line at this wattage. It becomes pretty obvious when the bias is set to high as the current goes way up.
The FETs are not heating up at this point.
If they're in parallel with others, remove them to see if the rest have approximately the same voltage across the resistors.
I'm assuming that the emitter resistors are all within tolerance and closely matched. If they're not, that could make it difficult to determine which transistors are passing the most current.
You should set the bias as low as possible it it doesn't affect the output (other than just a bit of crossover distortion).
I'm assuming that the emitter resistors are all within tolerance and closely matched. If they're not, that could make it difficult to determine which transistors are passing the most current.
You should set the bias as low as possible it it doesn't affect the output (other than just a bit of crossover distortion).
It's pretty clear that two I already replaced during this latest process are still carrying a majority of the load.
The closest meter I have to measure resistors that low is a Fluke 8050A which has a resolution of 0.01 ohms. After setting the relative point, I measured .13 ohms across the resistor that was on the first output I replaced and still has more load on it than the others.
The closest meter I have to measure resistors that low is a Fluke 8050A which has a resolution of 0.01 ohms. After setting the relative point, I measured .13 ohms across the resistor that was on the first output I replaced and still has more load on it than the others.
Class B and AB amps with high rail voltage will be very inefficient at low power. I'd suggest that you replace the emitter resistors (all of them, since you suspect that some are defective). clamp it into the heatsink and run it up to 100w/channel or so to see if the current draw still seems excessive.
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