before the amp cuts out it reads about .01v on all channels when it cuts out
the good channel stays at the same voltage but it has no transistors in that channel
the output transistors are the ones getting hot but i don't know how hot they normally run so i will start up one of my other amps and run it for a while and compare the temperature between the two
yes i have always had the transistors clamped down when running it
the good channel stays at the same voltage but it has no transistors in that channel
the output transistors are the ones getting hot but i don't know how hot they normally run so i will start up one of my other amps and run it for a while and compare the temperature between the two
yes i have always had the transistors clamped down when running it
The 2 between the driver ICs may be the bias pots.
Connect your meter to one center leg and one outer leg of an emitter resistor in the working channel. Measure the DC voltage. Turn the pots to see if either affects the voltage across the legs of the resistor. Adjust it for something near 0.001v DC.
Turn the pots slowly. In some amps, a very small change can make a large difference in current draw.
Connect your meter to one center leg and one outer leg of an emitter resistor in the working channel. Measure the DC voltage. Turn the pots to see if either affects the voltage across the legs of the resistor. Adjust it for something near 0.001v DC.
Turn the pots slowly. In some amps, a very small change can make a large difference in current draw.
I'm not sure what the pot in the power supply is used for. It may be used to set the rail voltage. If it's fully clockwise, set it back to the middle of its range for now.
You'll have to find those parts locally. They all appear to be available in the US. I'm not sure what's available in NZ.
You'll have to find those parts locally. They all appear to be available in the US. I'm not sure what's available in NZ.
http://octopart.com/
http://www.findchips.com/
I don't know which ones ship internationally. Use the search engines above to find the parts. Check with them to see if they will ship to NZ.
http://www.findchips.com/
I don't know which ones ship internationally. Use the search engines above to find the parts. Check with them to see if they will ship to NZ.
Did you try reducing the bias current with the bias pot?
Turn it very slowly while watching the current draw from the DC power supply. Set it at the point where it just barely causes an increase in idle current.
If you want to set it by the voltage across the emitter resistors, connect your meter (set to the lowest range of DC volts) to the center and one of the outside legs of one of the emitter resistors in the channel in which you're adjusting the bias current. Set the bias pot so that it reads between 0.001 and 0.005 across the emitter resistor. Let the amp idle (no audio) and recheck it after a few minutes.
Readjust it if it drifts. After you get the idle current right when the amp is cool, you'll have to drive it hard enough to get it hot (too hot to hold your hand on continuously). Recheck the idle current every few minutes by removing the audio signal and measuring the DC voltage on the emitter resistor. You can leave your meter connected during testing. If it drifts upward, reduce the biasing. If it remains OK when it's hot, the bias current is properly set.
Turn it very slowly while watching the current draw from the DC power supply. Set it at the point where it just barely causes an increase in idle current.
If you want to set it by the voltage across the emitter resistors, connect your meter (set to the lowest range of DC volts) to the center and one of the outside legs of one of the emitter resistors in the channel in which you're adjusting the bias current. Set the bias pot so that it reads between 0.001 and 0.005 across the emitter resistor. Let the amp idle (no audio) and recheck it after a few minutes.
Readjust it if it drifts. After you get the idle current right when the amp is cool, you'll have to drive it hard enough to get it hot (too hot to hold your hand on continuously). Recheck the idle current every few minutes by removing the audio signal and measuring the DC voltage on the emitter resistor. You can leave your meter connected during testing. If it drifts upward, reduce the biasing. If it remains OK when it's hot, the bias current is properly set.
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