Hi,
I am biasing an Adcom GFA-5802 amplifier and discovered that the transistor matching in the left channel was not done accurately. To get a nominal 33 mV across the .33 ohm source resistors of the IRF244 Mosfets one of the resistors measures 60 mV, way above the maximum 43 mV I should see. Since these transistors are no longer available would it make sense to install a larger value source resistor for this Mosfet in an effort to match it?
Thanks,
Will
I am biasing an Adcom GFA-5802 amplifier and discovered that the transistor matching in the left channel was not done accurately. To get a nominal 33 mV across the .33 ohm source resistors of the IRF244 Mosfets one of the resistors measures 60 mV, way above the maximum 43 mV I should see. Since these transistors are no longer available would it make sense to install a larger value source resistor for this Mosfet in an effort to match it?
Thanks,
Will
Hi Will,
When I was doing warranty service for Adcom, we had to match the mosfets ourselves. There was a requirement and a procedure for this. I believe those are still available aren't they?
Buy many from the same lot number and match them. I disagree completely with changing the emitter resistor value. Fix the problem, don't create more.
Your amplifier must have been repaired before, as dealer stock or a return to the dealer if you got it originally and didn't have it serviced yourself.
-Chris
When I was doing warranty service for Adcom, we had to match the mosfets ourselves. There was a requirement and a procedure for this. I believe those are still available aren't they?
Buy many from the same lot number and match them. I disagree completely with changing the emitter resistor value. Fix the problem, don't create more.
Your amplifier must have been repaired before, as dealer stock or a return to the dealer if you got it originally and didn't have it serviced yourself.
-Chris
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