• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Need help with MBLE full stereo 4-4 plus

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Hello, seeking info I stranded here on this forum. Apologize for my senses because my language is Dutch.
I hope someone can help me with my problem, I got a MBLE Full Stereo Amplifier 4 - 4 plus and I cleaned it. Removed dust, cleaned contacts end repaired the selector indicator. It works but not as it supposed to do. When it plays at a low volume the left side is much louder. When the volume goes up the balance need to correct to the center. Who knows whats wrong with it.

Peter
 
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Welcome to diyAudio Peter :)

If the left/right balance shifts with volume setting (and is basically normal at higher levels) then the problem may be nothing more than the two gangs of the volume control being poorly matched (a common issue). The only fix for that is replacement.

If the balance is consistently one sided throughout the whole volume range then more detailed investigation is needed as that would suggest a gain imbalance somewhere.
 
If you have not already tried, swap the valves over from side to side.
Try the ECC83s (shortest valves) first. Then the two EL84s. See if that changes anything. (The EZ81 will be fine.)

Have a look to see if any wires have come loose, especially the feedback wire from the output transformers. And round the volume / balance controls. You could try squirting a little switch cleaner into the pots as well.

I assume you have tested all the inputs and the fault is the same on all of them?
 
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