Board is inifhsed but there is problem, output is 5.5V with VR1 shorted and I need 5v.
any idea what the cause could be?
This is using the selected <7.5ma IDSS JFET for J3
any idea what the cause could be?
This is using the selected <7.5ma IDSS JFET for J3
All BC transistor Vbe are normal.
Vgs of M2 is 1.6V, 3-6V is the normal range according to an older post from you... could be the cause?
Vgs of M2 is 1.6V, 3-6V is the normal range according to an older post from you... could be the cause?
Yes all are correct, on negative reg all vbe between 0.6-0.7V and Vgs within 3-6V yet same problem.
Maybe a different resistor value than 270R for R5?
If all seems correct, replace LED1 with a regular diode.
If all seems correct, replace LED1 with a regular diode.
Yes, better have a try with more raw DC first. Because M1 drops enough out of it as Vgs and there is J1 to fit with enough VDS in that margin too.
R7 voltage is essentially 0 (0.04 on DMM)
Also -5.15V of neg reg does actually add up, vbe 0.65x2 + green led 1.9x2 , so dont think there is a problem. soekris can tolerate -5.5V so -5.15V is fine.
I upped to 15V input but behaviour is the same for pos reg.
Also -5.15V of neg reg does actually add up, vbe 0.65x2 + green led 1.9x2 , so dont think there is a problem. soekris can tolerate -5.5V so -5.15V is fine.
I upped to 15V input but behaviour is the same for pos reg.
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On R7 we need enough drop, say 0.54V, showing that 2mA bias is running in the J2 Q3 Q2 chain. More is ok depending on idss, but no less than one mA in any case.
OK so we exclude that. Check that Q4 gives a logical Vbe measurement too.
R1 voltage drop divided by R1 Ohms should also indicate the programmed constant current you targeted.