Beomaster 1900-2 to low volume

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nongrata Posted: Tue, Mar 15 2016 9:29 AM

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Bought a second hand Beomaster 1900-2 that should work good. But the sound was (left and right) to low on tape and radio (phono not tested).

It does not distort but the volume in general is simple to low. Changed the lamp and LDR module but no difference. 

The unit looks quite good when it comes to the capacitors (no cracks or brown stuff). 
The volume was so low even with headphones you could not listen to it.
I could increase the volume by adjusting the trimpot R136 to maximum

With headphones and the volume on maximum the units is now usable. 
When used with speakers full volume is however still to low.
As far as i can measure the output darlington look fine.
Ik think the problem is in the pre amp section.

The top PCB with treble , balance and bass sliders is fine (exchanged it, no difference) 

I changed the bad lamps so this can not cause any trouble.

Does anyone have an idea what might cause the low volume ? 
Maybe someone knows how to change the circuit to increase the level more then by adjusting r136 to the max ?