Shruthi-1 SMR-4 mkII filter board power supply testing

Hello everybody,

My power supply testing shows + 3.73V (red points) and 3.73V (green points). I checked the regulators and capacitors polarities. Everything is looking good. I used a 9V adapter (Center positive), Output 9V 1700mA. All the red and green points are consistent 3.73V + red and green.

I did had to source a single 10pF capacitor with a number 100. The one and only that came with the kit got damaged (my fault). The self sourced 10pF capacitor looks a bit different but they are what they supposed to be and have a number 100 on them.

Any ideas on why my Voltage measurements are way off?

Thank you,


Multimeter battery? Multimeter set to AC mode?

That was the first thing I did. Changed the 9V battery. No change.
Multimeter is set to 20V.

I am going to try a friends multimeter just to be sure.

What voltage are you measuring at the input connector (9V)?

20V what? AC or DC?

I am positive that its 20V DC. The multimeter will show a power thunder logo if its in AC mode.

The input connector is measuring 9.52V

I tried another power adapter. 9V DC 500mA center pin positive. Now its + 6.62V Red points and

  • 6.31V Green points.

Its a cheap Gardner Bender Multimeter GDT-311. Could it be just a shitty multimeter by any chance?

Maybe you have swapped the two regulators?

Yes thats what it was. I swapped the regulators. Now I have +5.01V on Red Points and -4.97V on Green points. That seems to be right.

Thank you for your help.