earckens
Active Member
In the schematic attached there is transistor Q5 (C1815 SOT-23, spec sheet attached) that in theory should withstand the conditions to which it is subject:
Vcb max 60V, Vce max 50V, Ic max 150mA, Pc max 200mW.
When running this pcb in test modus, with a small 1000µF 63V condensor, all runs ok, hours on end.
Yet when even one single 4700µF 63V condensor is connected, the circuit output goes into oscillation after some time (ie output voltage fluctuates +/- 5 to 10V), and, as was the case just now, suddenly burns out Q1 (and takes the LM723 with it).
Condensor Vcc = 46V.
What could be going on, except for the fact that in theory things should be fine?
How to remedy?
EDIT: C7 has been replaced with a 100µF condensor, the 18Vdc line is free of any ripple.
Vcb max 60V, Vce max 50V, Ic max 150mA, Pc max 200mW.
When running this pcb in test modus, with a small 1000µF 63V condensor, all runs ok, hours on end.
Yet when even one single 4700µF 63V condensor is connected, the circuit output goes into oscillation after some time (ie output voltage fluctuates +/- 5 to 10V), and, as was the case just now, suddenly burns out Q1 (and takes the LM723 with it).
Condensor Vcc = 46V.
What could be going on, except for the fact that in theory things should be fine?
How to remedy?
EDIT: C7 has been replaced with a 100µF condensor, the 18Vdc line is free of any ripple.
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