DIY - Change capacitors - Scott A436






hifi amp





Stereo Amplifier Scott A436




SERVICE MANUAL SCOTT A436

Free Download Service Manual


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danger

Purpose of the operation: Complete renewal of electrochemical capacitors.
Adjusting the BIAS output transistors (quiescent).
Cleaning the knobs and different contacts.
Note: For marking of components on the PCB, they can be wrong. Do not overheat welding because the tracks tend to peel off.


1 / Taking the measure of restoration before quiescent current.
2 / A photograph of the card.
3 / Use a marker to identify the polarity of the capacitors with a marker.
4 / Change capacitors one by one to avoid an error.
5 / Treat welds and pay close attention to the polarities.
6 / Before reconnection, do a check of the cards.

Adjusting the BIAS after changing all capacitors..

Setting the quiescent currents (powers of the amplifier circuits).
Do not apply signal to the input of the amplifier, volume 0.
Output terminals of senior speakers: nothing connected.
Use only a multimeter, and know the precautions and safety measures face a unit. The voltages in the device approaching 250 volts!

Left Channel:

Adjust the variable resistor (R808) check the voltage between (A and B) and adjust to 8 milivolts quiescent current.

Right Channel:

Adjust the variable resistor (R833) and check the voltage at points (A and B) and adjust to 8 milivolts quiescent current.

Results:

A transformed amplifier, very musical, a much more detailed.
A great device, this Scott amplifier A 436. A vintage amp that I recommend!



Transistors Equivalent Transistors Equivalent
2SC 733 BC 182L/2N 3710 2SC 372 BC 184L/BC 237B
2SA 495 BC 214LB 2SC 1000 BC 184L/2N 3707
2SA 682 BD 442/NTE 374 2SC 1382 BD 139/2N 5192
2SC 793 BU 123/2N 5157 2SC793 BDY20-2N3055


Change capacitors on Scott A436

Change capacitors on Scott A436

Change capacitors on Scott A436

Change capacitors on Scott A436

Change capacitors on Scott A436

Change capacitors on Scott A436

Change capacitors on Scott A436

Creating Loudness for Scott A436

More potentiometers with Loudness plug! Here is a trick to fix it: Resistance of a 1/2 W in series with the potentiometer (100 KB), on each channel, of course, the loudness function will be able to work, but at the expense of travel. A resistance of 100 k, but will increase the work stroke of significantly potentiometer. 50k is a better solution, to adjust to your taste also for more or less serious.



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