You might want to copy this tutorial and the previous one to complete the pdf.
If one might still have questions feel free to ask in this thread or PM me.
Testing the C.H.Amp (
after the power supply checked out O.K.)
Insert the audio opamps (IC1, IC2, IC3, IC8, IC9 and IC10).
Solder the power supply connections (use a small wire and solder that, or simply put a blob of solder across the power jumpers (JP1, JP2, JP3, JP4).
Set jumper: JP13
remove ALL other jumpers
Connect a trafo (15V-0-15V) to CON4
Power up the amp.
Put the black lead of the multimeter (MM) on the GND pad (GND1)
Put the red MM lead on R51 (the pad next to the middle of the output relay)
The multimeter must be in DC-V position (if you need to select ranges, select 20V)
There should be almost 0V (+/- 100mV) output voltage.
Now set jumper JP18 and see if the the DC voltage is 0V (+/- 50mV)
With some IC's the DC offset voltage might even be below +/- 10mV, with others a bit higher.
If DC voltages are above the specified values, power down and figure out if any opamps are defective (by simply replacing them)
In case the voltages are still not within parameters … contact me.
Power down.
Set jumpers JP11, JP12,JP13
remove jumper JP18 again.
Do the same voltage check as above.
DC offset voltages are probably higher than before but should not exceed 0V (+/- 100mV)
Set jumper JP18 again.
The offset voltage should be smaller again 0V (+/- 50mV)
The output relay should be activated.
Check if the output connector CON6 has the same DC offset voltage as the pad on R51
Another way to check if the relay is activated is by checking the coil voltage or by checking for continuity (with the amp on) between the output pin (CON6) and R51 pad (next to the middle of the relay)
If this is O.K. the other channel must be checked:
Remove the trafo from CON4.
Set jumper: JP23
remove ALL other jumpers
Connect a trafo (15V-0-15V) to CON5
Power up the amp.
Put the black lead of the multimeter (MM) on the GND pad (GND2)
Put the red MM lead on R52 (the pad next to the middle of the output relay)
The multimeter must be in DC-V position (if you need to select ranges, select 20V)
There should be almost 0V (+/- 100mV) output voltage.
Now set jumper JP28 and see if the the DC voltage is 0V (+/- 50mV)
Power down.
Set jumpers JP21, JP22,JP23
remove jumper JP28 again.
Do the same voltage check as above.
DC offset voltages are probably higher than before but should not exceed 0V (+/- 100mV)
Set jumper JP28 again.
The offset voltage should be smaller again 0V (+/- 50mV)
The output relay should be activated.
Check if the output connector CON6 has the same DC offset voltage as the pad on R52
Another way to check if the relay is activated is by checking the coil voltage or by checking for continuity (with the amp on) between the output pin (CON6) and R52 pad (next to the middle of the relay)
If this checks out O.K. you must
check the DC protection for proper operation.
For L channel:
Set jumpers: JP10, JP13
remove all other jumpers.
Mount a 1 leg of a 390k resistor on the left input connector (CON7)
Connect only 1 trafo to CON4 (CON5 no transformer)
Switch on the amplifier.
The relay should be activated after a few seconds (LED must light up more)
Connect a 1.5V battery (size is not important) with the – ground of CON7
Connect the 1.5V battery with the + to the open leg of the 390k resistor.
The relay must switch off, the voltage on R51 should be around +0,9V (+/- 0,1V)
CHECK that there is NO voltage present on the output (CON6)
If O.K. disconnect the battery.
The relay should be activated again after a few seconds.
Now connect the + of the battery to ground and the – of the battery to the open leg of the resistor.
The relay should be deactivated again and the voltage on R51 should be around -0,9V (+/- 0,1V)
CHECK that there is NO voltage present on the output (CON6)
For R channel:
Set jumpers: JP20, JP23
remove all other jumpers.
Mount a 1 leg of a 390k resistor on the right input conector (CON8).
Connect the trafo to CON5 (CON4 no transformer)
Switch on the amplifier.
The relay should be activated after a few seconds (LED must light up more)
Connect a 1.5V battery (size is not important) with the – ground of CON8
Connect the 1.5V battery with the + to the open leg of the 390k resistor.
The relay must switch off, the voltage on R52 should be around +0,9V (+/- 0,1V)
CHECK that there is NO voltage present on the output (CON6)
If O.K. disconnect the battery.
The relay should be activated again after a few seconds.
Now connect the + of the battery to ground and the – of the battery to the open leg of the resistor.
The relay should be deactivated again and the voltage on R52 should be around -0,9V (+/- 0,1V)
CHECK that there is NO voltage present on the output (CON6)
If this procedure is completed the amp can be connected and tried with a cheap (sacrificial) headphone.
At first attempt I would remove JP10 and JP20.
If the amp sounds O.K. they can be set again (or left out as desired, see manual)