Buck Regulator with error on PCB

VK2RK

Active member
If using this voltage buck regulator be advised that the manufacturer has an error on the PCB that causes the unit not to behave as expected.
From the image it can be seen that one can select one of the seven output conditions, when I tested the unit I found that the output voltages were not as expected, selecting the 5V produced a voltage below this figure, that the variable control altered the output voltage but not reach 5 Volts.
Tracing the board revealed that the manufactures had the variable control permanently connected, requiring to cut the track.
After this the selected voltages behaved as expected.
s-l1600.jpg
 

VK3ZYZ

Moderator
Good find.
I suppose they may do that so it defaults to 1.25V, but it would help if it was noted as such.
 

VK2RK

Active member
Good find.
I suppose they may do that so it defaults to 1.25V, but it would help if it was noted as such.
No, it does not default to 1.25V, the pot is in parallel to any of the selected values, so you dont get the selected voltage, for example selecting the 8 Volts then via the pot you get to adjust to the five volts, defeating the concept.
As I said cut the track and any voltage selected on the pads then the output is what is stated on label.

The data sheet shows that the voltage is set via a divider.
 

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VK3ZYZ

Moderator
Oh, yes! I should have realized that. I was thinking it was at gnd for some reason.
Blame pre-coffee ;)
 
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