Servo-Sound made in Belgium

[secret]

km processor pr2

Hello,

I'm talking about the one that is the pre-amplifier ( see attached fotos) BUT my description will help you to find out what is in any blackbox ( servo sound , KM )

Detail : the blackbox is just plastic and is surrounding the epoxy.

If you squeeze the plastic , it comes off, and shows you a brown epoxy box.

Also interesting : on the KM-52 speaker , there is no blackbox on the double-sided pcb !!

my english is very bad, y have tried to open a black box of processor KM PR2, but i have lost the values of resistors and capacitors.

Have you establish a schema of the circuit pro 05 and the black box so5

best regards

 

[dapepe]

blackbox preamplifier PR2 and PR6

Patent FR_2208155_A1-1.pdf is describing the idea what is inside the blackbox of the PR2 , PR6 pre-amplifier ( KM )

Compared blackboxes , some differences exist

Attached schematic of the servo-sound 15b amplifier

Whats next ?

 

[bentoronto]

Can somenody explain that circuit to me. It is drawn for maximum impenetrability - not to mention the crucial board that is blank.
B.

 

[dapepe]

servo-sound SL70 pre-amplifier

Hello,

In attachment you can find the schematic of the pre-amplifier.

T1 and T2 = RIAA amplifier , output 100mV

All line levels (100mV) .

Between T2 and T3 we find a lattice network (stereo crossing) that is described in patent US3659217
Due to this network , the 100mV line level is attenuated to 30mV.
This weak 30mV signal is then appied to T3

After T3 we find tone controle circuit with P1(10K) and P2(10K) bass , treble

P3(10K) : logically balance control

P4(10K) : volume control with RC equal loudness compensation network

Output of T4 = 30mV ?

250mV signal level goes to T5

T6 final amplifier stage , output signal 250mV

Signal coupling capacitors : phono : C1 and C7 = 2,2µF
line level : C15, C22, C24, C27, C29, C30

All transistors BC154

Power supply comes from speaker , RC filters : R45+C31 , R45+C17, R12+C6,

Power supply for phono : double RC filter : R12+C6 and R5+C3

Regards,

Peter

 

[bentoronto]

Can somebody now tell me how the amp works? Is it just a complicated way of mixing the bass?

B.

 

[dapepe]

Hello everybody,

First of all best whishes for 2017.

I finally finished dismantling the blackbox of the PR2-2 preamplifier.
I measured all the values .
Since I got expierenced in dismantling 2 blackboxes of preamplifiers I could now start with the blackbox inside de servo-sound speaker, pcb type 15b .....
if you folks are still interested ?

Regards,

Peter