1. A thump sound when switching sources is normal.

2. Check the idle currents. If set too high the transformer will be heavily loaded (and the bottom of the Beomaster 1200 will run warm). 

Martin 

Thanks Martin (again)

I will accept the tbumb :- ) just strange when it is only in L position....

Idle current is good 7,5 mV.…tge trafo dont go escpecially hot.
I think its mecanical - the bottom plate have been "twisted" a bit, due to what I dont know….

Torben

Hi

The thumb switching to phono input in LO position is yet too loud.....one day, when I or someone forget to turn volume down to min., it will blow my speakers.

Switching other inputs is good, a nice little thumb is heard :- ) only problem is "to" and "from" phono in LO. Not in HI.

Investigating the schematic I could see that parts of the preampsection has separate L and R "grounds" connected to switch 37/38. And that these, when set LO, are lead to common ground on phono input (switch 37/38). 

When on another input than phono, these two "grounds" are different voltage, ca. 1 v. 
My theory is that when these are connected or disconnected the voltagedifference (amplified in powersection) gives the loud thumb.

Changing/matching transistors 21 and 22 a lot of times has reduced the difference in voltage to ca. 0,2 V - and reduced thumb.

Question: Could I place a large resistor ex. 700K between to two grounds to reduce thumb further?

Regards Torben

Schematic preampsection

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