Premier 8 (2) led's stay on
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Premier 8 (2) led's stay on
I had the cable from my pre-amp go bad (intermittent connection to short when I bumped the preamp while listening. Loud noise came out then the lights came on. I figured I had blown the fuse or the tubes. The Premier 8 mono block now has (2) biasing lights stuck on (either powered up or not). I checked the fuse, swapped all tubes from the other amp and still the lights stay on. BUT, the amplifier seems to work fine. I don't really know how the Bias circuit and lights work, but there are some 2N5061 transistors tied into the led. I am trying not to risk shipping to CJ since during the last shipping, the foam deteriorated, and I almost had a disaster. Any suggestions on what to check, replace, or any schematics would be of great help.
Re: Premier 8 (2) led's stay on
First, welcome to CJO! Great to have you with us.
Sorry you are having this issue. It seems like you did the correct investigation by checking the fuse and the tubes. When the LED light stays on like that, it's supposed to be signaling a bad tube I believe. But if you swapped in a new set of tubes and it's still good, then perhaps something went wrong in the biasing circuit. Just for clarity, did you swap all the tubes or just the ones with the LED staying on?
Luckily, we do have the Premier 8's schematics in our database so you can download those and take a look: https://www.conradjohnsonowners.com/viewtopic.php?t=128
Good luck, and let us know how it goes.
Sorry you are having this issue. It seems like you did the correct investigation by checking the fuse and the tubes. When the LED light stays on like that, it's supposed to be signaling a bad tube I believe. But if you swapped in a new set of tubes and it's still good, then perhaps something went wrong in the biasing circuit. Just for clarity, did you swap all the tubes or just the ones with the LED staying on?
Luckily, we do have the Premier 8's schematics in our database so you can download those and take a look: https://www.conradjohnsonowners.com/viewtopic.php?t=128
Good luck, and let us know how it goes.
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Home Theater in Member Gallery
Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
Home Theater in Member Gallery
Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
Re: Premier 8 (2) led's stay on
Hola accjohn,
Reading you, I know you had tried to adjust the bias too. If the bias tube variable pot is all the way to the top counterclockwise direction, it is indicating that the tube is bad or the 5Watt 20 ohms bias resistor is open. Usually bad tubes could make to burn this resistor. Also swap the 6550 for the one that is not lit. If the same tube in other position the bias LED is on and so for on bias leds, those tubes need to be replaced. You do not need to change all the tubes. In other brands of power amps, you need to use matched pair tubes. With Conrad Johnson, you don't need this.
This is the procedure for adjusting the bias:
Biasing the amplifier is a simple procedure that can easily be done by the owner. Only a plastic screwdriver is required. A red plastic screw- driver has been included with your amplifier for this purpose. After replacing the tubes, the amplifier should be connected to a load (your loudspeakers will work fine) and there should be no signal applied to the amp. It should be connected to you preamplifier with the volume control turned fully down. Turn the amplifier on. After about one minute, turn each of the four screwdriver adjustable controls counterclockwise until the associated indicator LED just goes off. Clockwise rotation may be necessary first to turn the LED on; do not turn the adjusting screw any further in the clockwise direction once the LED has come on.
Happy listening!
Reading you, I know you had tried to adjust the bias too. If the bias tube variable pot is all the way to the top counterclockwise direction, it is indicating that the tube is bad or the 5Watt 20 ohms bias resistor is open. Usually bad tubes could make to burn this resistor. Also swap the 6550 for the one that is not lit. If the same tube in other position the bias LED is on and so for on bias leds, those tubes need to be replaced. You do not need to change all the tubes. In other brands of power amps, you need to use matched pair tubes. With Conrad Johnson, you don't need this.
This is the procedure for adjusting the bias:
Biasing the amplifier is a simple procedure that can easily be done by the owner. Only a plastic screwdriver is required. A red plastic screw- driver has been included with your amplifier for this purpose. After replacing the tubes, the amplifier should be connected to a load (your loudspeakers will work fine) and there should be no signal applied to the amp. It should be connected to you preamplifier with the volume control turned fully down. Turn the amplifier on. After about one minute, turn each of the four screwdriver adjustable controls counterclockwise until the associated indicator LED just goes off. Clockwise rotation may be necessary first to turn the LED on; do not turn the adjusting screw any further in the clockwise direction once the LED has come on.
Happy listening!
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