Bias - DC offset - Luxman 5L15

[søren krabbe]

hey all
I´ve got a Luxman 5L15 amp. its running ok - but - the right channel have a little higher dc offset than the left channel 26mV compared to left channels less than 10 mV. One funny thing is that the DC-offset indicator blinks red according to the music played, BUT only for the left channel, which is the one with the lowest DC offset???? Strange
Also you can feel that the rightside heatsink is warmer that the leftside heatsink, so is the powertransistors.
I have tried to adjust the bias by turning the (vr)TR701, but it doesn´t seem to make any difference.
Any good advice in this matter?

link to schematics: https://drive.google.com/file/d/1CvCbhkGZnEBsA8fLxjPyDDbtm0EjZub1/view?usp=sharing

by the way - does anybody have a better copy of schematics?
thanks in advance
Søren

 

[Binkman]

https://www.hifiengine.com/manual_library/luxman/5l15.shtml
Sorry no time to dig up a SM.

I read through the owners manual and describes the LED...
This unit may not have dc offset setting / bias.. for which are unrelated.. but curious that you readings aren't all the high for dc offset. So maybe fire and forget. Q? the balance knob has no effect on the offset lamp.. like does it really matter or just some engineers idea of another led.

 

[petehall347]

set to input capacitor

 

[søren krabbe]

https://www.hifiengine.com/manual_library/luxman/5l15.shtml
Sorry no time to dig up a SM.

I read through the owners manual and describes the LED...
This unit may not have dc offset setting / bias.. for which are unrelated.. but curious that you readings aren't all the high for dc offset. So maybe fire and forget. Q? the balance knob has no effect on the offset lamp.. like does it really matter or just some engineers idea of another led.

Yes the balance knob has effect on the red offst lamp - it only blink away to the music in the left side. When the balanceknop is turn to the right there is no red light

 

[søren krabbe]

set to input capacitor

can you elaborate on that I don´t understand what you mean

 

[petehall347]

it is in the manual . says when red light blinks to flick the switch up on the rear panel ..
you try swapping inputs over first as i suspect dc is coming from the source .

 

[søren krabbe]

it is in the manual . says when red light blinks to flick the switch up on the rear panel ..
you try swapping inputs over first as i suspect dc is coming from the source .

Thanks - Now it makes a lot of sense - I´ll try that switch

 

[petehall347]

yes ..send dc in and dc comes out . hoping its that simple .

 

[Blue Shadow]

yes ..send dc in and dc comes out . hoping its that simple .

And that DC is usually amplified so this can cause the red light.

Good idea to swap left and right inputs to the amp, too just to see if that changes the red light indicator to the other channel.

 

[Goldie99]

Maybe worth checking with an alternative source as well.

In the worst case, a couple of the guys above have 'been there before'. It may not be totally relevant yet, but worth a read anyway..... http://audiokarma.org/forums/index.php?threads/luxman-5l15-dc-offset.462506/#post-5964905