There are three opamps, so typical consumption is 12mA (but conditions for typical are not very clear in the datasheet), maximum 24mA.
The instability at unity gain unless an external compensation capacitor is used at OP2 is my concern
The instability at unity gain unless an external compensation capacitor is used at OP2 is my concern
The amp runned over 30 years like this, now there is a problem somewhere that make the BC640 to burn. Tell me if im wrong but there is probably something on the 18v negative rail shorted that take too much current for the BC640 and make it run too hot until it finish to burn.
Lift the emitters of the two regulator transistors and put 100R 1W in series.
Then you will be able to measure the drop and calculate current. A volt or so drop won't make any difference to the opamps
Then you will be able to measure the drop and calculate current. A volt or so drop won't make any difference to the opamps
If I do the same but instead of using a 100R I use the DMM in serie on the mA scale I will get the current or Im better with your method?
Using a current meter -
you can only do one side at a time
long leads may cause instability
unexpected high current blows meter fuses
you can only do one side at a time
long leads may cause instability
unexpected high current blows meter fuses
I recommend that you never use your ammeter function, unless there is no other way to do a current measurement.
Inserting a low value resistor and measuring volts drop is far more effective.
If you have a meter that resolves 0.1mVdc, you can resolve currents down to 0.1µA with 1k0 resistor, or down to 1µA with a 100r resistor. Even a 1r0 resistor allows resolution down to 0.1mA
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