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If I were to re-bias my SS amp, how would I measure the DC offset voltage and quiescent current? At the speaker terminals with no signal going in? Should the speakers still be connected? Do I need some resistor there to measure the current?
Follow Ups:
Goto TNT website.click on tweak\diy then look for "put a tiger in your amp".You will need to make sure theres adequate Heatsinking in your amp.Emmiterresistors are usually the biggest resistor probably near the output transistor.
Happy listening mikee55
Thanks! I read it. There are two special looking resistors near the output devices in the amp. One has a coil wrapped around it and one is raised of the PCB (for heat?). Would one of those be the emitter resistor for the quiescent current?
Can you do a continuity check to see if the resistor connects to the emitter leg of the transistor?The other side is to gnd,I believe.I think the resistor with coil is a zobel network or somthing like that which is usualy on the output.Is the resistence low on the non-coil one?It usualy is.Put your voltmeter on the resistor,adjust the pot to see if the voltage changes.This is how you can set the bias
volts divided by resistor value = bias current
Mikee55.
Quiescent current may be computed by measuring the voltage across the emitter resistors on the output devices and dividing by the amount of resistance. DC offset may be measured at the speaker terminals. These measurements are taken with no signal and speakers disconnected.I agree with the other posters: if you've never done this before, it is best to have a professional do it.
Ed
Probably... But where do I find the emitter resistors?
Do you have the service manual? The service manual for my NAD S300 explains how to rebias the output stage via measurement points and trimpots for each dual mono channel. Maybe your amp's service manual will have this info too...
If you don't know the basic set-up and measurements for biasing a solid state amp, it is best left to someone who does. You run the risk of destroying the output devices very quickly.
Why do you need to re-bias anyway?
Since it's four years old and has probably drifted from the original set up.
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