Andrew the data I supplied may have been misleading Vg13.1 and Vd 13.1 just happened to be equal. I don't get continuity between them (at least when power is off).
I took another data point with variac a bit higher to give -18.7 at source pin.
Now Vg is -15.3 and Vd is still -13.1.
So Vgd is 2.2
It seems to me that on the CCS FET the gate to drain relationship is wrong?
So it seems to me there are two possible causes:
A) the gate to drain relationship for the CCS FET is wrong or
B ) The shunt FET is not conducting enough current to ground.
Now I notice that Vg for the shunt FET is about 3 volts bigger on the side that is out of range (negative side).
So perhaps I need to troubleshoot the part of the circuit that sets the gate voltage at the shunt FET?
Does tha sound right or am I off course?
I took another data point with variac a bit higher to give -18.7 at source pin.
Now Vg is -15.3 and Vd is still -13.1.
So Vgd is 2.2
It seems to me that on the CCS FET the gate to drain relationship is wrong?
So it seems to me there are two possible causes:
A) the gate to drain relationship for the CCS FET is wrong or
B ) The shunt FET is not conducting enough current to ground.
Now I notice that Vg for the shunt FET is about 3 volts bigger on the side that is out of range (negative side).
So perhaps I need to troubleshoot the part of the circuit that sets the gate voltage at the shunt FET?
Does tha sound right or am I off course?
Today i've rebuilt the DCB1 on a better pcb (etched by myself) and used only good quality components but on the positive reg something is wrong.
I have the following measured parameters:
IN=15v,
Out=14,25V,
Across 3 leds=5,5v
Across 5 Leds=12,75v
Across R that sets the current (10ohm)= 0,83
Any clue what to check ?
I have the following measured parameters:
IN=15v,
Out=14,25V,
Across 3 leds=5,5v
Across 5 Leds=12,75v
Across R that sets the current (10ohm)= 0,83
Any clue what to check ?
Attachments
The negative rail is working and measuring good without load.
I've measured Gate-Souce voltage and i have 4.6V on CCS and on the other mosfet i have 0v.
The leds are a bit lower than the other rail. The red leds are 1.8 and the green ones are 2v.
After the other channel is working i will install also some heatsinks. Is strange because i had the DCB working but i wanted to use a better pcb and the delay based on relay.
I've measured Gate-Souce voltage and i have 4.6V on CCS and on the other mosfet i have 0v.
The leds are a bit lower than the other rail. The red leds are 1.8 and the green ones are 2v.
After the other channel is working i will install also some heatsinks. Is strange because i had the DCB working but i wanted to use a better pcb and the delay based on relay.
I've solved the shunt. The problem was a resistor not soldered well.
Now i'm fighting with the relay part. The relay does not click, after few seconds voltage goes to 0.8V across relay. If i make a shortcircuit between Base and Colector of the second transistor the relay clicks. I'm using 2xBC546C and two paraleled resistors 560R as i'm using a 5V relay. I tried to change the electrolitic from 100uf to 47 uf but only change is the time when reaches 0.8V and that's all.
The circuit is so simple ... and is impossible to find the problem.
Now i'm fighting with the relay part. The relay does not click, after few seconds voltage goes to 0.8V across relay. If i make a shortcircuit between Base and Colector of the second transistor the relay clicks. I'm using 2xBC546C and two paraleled resistors 560R as i'm using a 5V relay. I tried to change the electrolitic from 100uf to 47 uf but only change is the time when reaches 0.8V and that's all.
The circuit is so simple ... and is impossible to find the problem.
Attachments
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